@article{KastenmeierSchmidEhrlichetal., author = {Kastenmeier, Andreas and Schmid, Vinzent and Ehrlich, Ingo and Petratos, P. and Mourtos, N. and Trafalis, T.}, title = {Specimen Preparation and Material Characterization of Filament Wound GFRP Composite Tubes}, series = {Athens Journal of Technology \& Engineering}, volume = {4}, journal = {Athens Journal of Technology \& Engineering}, number = {3}, pages = {191 -- 205}, abstract = {Filament wound composite structures are widely used in the field of pressure vessels, tubes, pipelines or rocket cases. The mechanical behavior of these structures is typically different from those of flat laminated structures due to an alternating lay-up sequence, winding tension and manufacturing induced imperfections. However, design and analysis issues require the same engineering data as used for laminated structures in general. It has therefore become necessary to establish an accompanying quality assurance procedure following the production process to identify the material properties of the manufactured tubes especially for the single layer. Consequently, there are three different approaches of determining the elastic moduli and tensile strengths of a filament wound laminate. Either specimens are resected from a curved tube, from a tube with plane areas or standardized flat specimens are manufactured under deviating production conditions. All approaches entail disadvantages, whether in terms of manufacturing or testing parameters including geometry, lay-up sequence, porosity, fiber tension and load direction. This study presents the discrepancies in the determination of mechanical properties of a filament wound glass-fiber-reinforced polymer tube on curved or cylindrical specimens and flat specimens produced to meet the specifications of international standards. In order to obtain material properties not only in longitudinal but also in transverse direction of the tubes, the so-called split-disk tensile test modeled after ASTM Standard D 2290, is used with tube segments.The procedures of specimen production and preparation are described in detail. Material properties such as the fiber volume and void content of the composite specimens are conducted in order to consider quality and production differences. Finally tensile tests are performed and the results are compared and discussed.}, language = {en} } @article{FrazzicaBrancatoDawoud, author = {Frazzica, Andrea and Brancato, Vincenza and Dawoud, Belal}, title = {Unified Methodology to Identify the Potential Application of Seasonal Sorption Storage Technology}, series = {Energies}, volume = {13}, journal = {Energies}, number = {5}, publisher = {MPDI}, address = {Basel}, doi = {10.3390/en13051037}, pages = {1 -- 17}, abstract = {In this study, the definition of a new methodology for a preliminary evaluation of the working boundary conditions under which a seasonal thermal energy storage (STES) system operates is described. The approach starts by considering the building features as well as the reference heating system in terms of solar thermal collectors' technology, ambient heat sinks/source, and space heating distribution systems employed. Furthermore, it is based on a deep climatic analysis of the place where the STES needs to be installed, to identify both winter and summer operating conditions. In particular, the STES energy density is evaluated considering different space heating demands covered by the STES (ranging from 10\% up to 60\%). The obtained results demonstrate that this approach allows for the careful estimation of the achievable STES density, which is varies significantly both with the space heating coverage guaranteed by the STES as well as with the ambient heat source/sink that is employed in the system. This confirms the need for careful preliminary analysis to avoid the overestimation of the STES material volume. The proposed approach was then applied for different climatic conditions (e.g., Germany and Sweden) and the volume of one of the most attractive composite sorbent materials reported in the literature, i.e., multi-wall carbon nanotubes (MWCNT)-LiCl, using water as the working fluid, needed for covering the variable space heating demand in a Nearly Zero Energy Building (NZEB) was calculated. In the case of Swedish buildings, it ranges from about 3.5 m3 when 10\% of the space heating demand is provided by the STES, up to 11.1 m3 when 30\% of the space heating demand is provided by the STES.}, language = {en} } @article{VoyerPeterlechnerNoster, author = {Voyer, Joel and Peterlechner, Christian and Noster, Ulf}, title = {Flame sprayed Al-12Si coatings for the improvement of the adhesion of composite casting profiles}, series = {Journal of Thermal Spray Technology}, volume = {17}, journal = {Journal of Thermal Spray Technology}, number = {5-6}, publisher = {Springer}, address = {Boston, Mass.}, issn = {1544-1016}, doi = {https://doi.org/10.1007/s11666-008-9235-8}, pages = {824 -- 830}, abstract = {In this study, flame sprayed Al-12Si coatings were produced on the surface of inlays (aluminum profiles) of composite castings parts. The aim was to enhance the strength between the joining partners inlay and cast. Due to the high surface roughness and the presence of pores in the coatings, combined with the formation of an intermetallic phase at the interface, the adhesion of flame sprayed inlays could be enhanced by a factor of 2 compared to blank inlays and by a factor of 1.3 when compared to sand-blasted inlays. However, results also show that gaps are present, mostly at the interface between the inlays and the flame sprayed coatings, and these gaps have a negative effect on the joining strength of the composite casting parts. Therefore, optimizing the adhesion of the coating on the Al profiles via an improvement in both the sand-blasting and the flame spraying parameters would be beneficial for further enhancement of the adhesion of composite casting parts.}, language = {de} } @inproceedings{LangBeckeSchlegl, author = {Lang, Jonas and Becke, Mark and Schlegl, Thomas}, title = {A Systematic Approach for the Parameterisation of the Kernel-Based Hough Transform Using a Human-Generated Ground Truth}, series = {Intelligent Robotics and Applications}, volume = {9244}, booktitle = {Intelligent Robotics and Applications}, editor = {Liu, Honghai and Kubota, Naoyuki and Zhu, Xiangyang and Dillmann, R{\"u}diger and Zhou, Dalin}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-22878-5}, doi = {10.1007/978-3-319-22879-2_44}, pages = {473 -- 486}, abstract = {Lines are one of the basic features that are used to characterise the content of an image and to detect objects. Unlike edges or segmented blobs, lines are not only an accumulation of certain feature pixels but can also be described in an easy and exact mathematical way. Besides a lot of different detection methods, the Hough transform has gained much attention in recent years. With increasing processing power and continuous development, computer vision algorithms get more powerful with respect to speed, robustness and accuracy. But there still arise problems when searching for the best parameters for an algorithm or when characterising and evaluating the results of feature detection tasks. It is often difficult to estimate the accuracy of an algorithm and the influences of the parameter selection. Highly interdependent parameters and preprocessing steps continually lead to only hardly comprehensible results. Therefore, instead of pure trial and error and subjective ratings, a systematic assessment with a hard, numerical evaluation criterion is suggested. The paper at hand deals with the latter ones by using a human-generated ground truth to approach the problem. Thereby, the accuracy of the surveyed Kernel-based Hough transform algorithm was improved by a factor of three. These results are used for the tracking of cylindrical markers and to reconstruct their spatial arrangement for a biomedical research application.}, language = {en} } @article{ProverbioCalabreseCaprietal., author = {Proverbio, Edoardo and Calabrese, Luigi and Capri, Angela and Bonaccorsi, Lucio Maria and Dawoud, Belal and Frazzica, Andrea}, title = {Susceptibility to corrosion of aluminium alloy components in ethanol adsorption chiller}, series = {Renewable energy}, volume = {110}, journal = {Renewable energy}, publisher = {Elsevier}, doi = {10.1016/j.renene.2016.08.042}, pages = {174 -- 179}, abstract = {Methanol, and more recently ethanol, have been deeply employed as adsorbate phase (refrigerant) in adsorption chiller and heat pump applications (e.g. refrigerator adsorption ice maker). The use of anhydrous alcohols however can cause several problems related to the corrosiveness of such molecules towards light alloys (from titanium to aluminium). The problem was already highlighted in bio-fuel technology where bio-ethanol was considered as a promise alternative to fossil hydrocarbons. Water content was observed as one of the main factors influencing corrosion rate. In the present works several accelerated corrosion tests on 6061 Aluminium alloy have been carried out in autoclave in a temperature range from 110 to 135 degrees C with different ethanol to aluminium mass ratio. Highly exothermic reactions related to aluminium oxidation, coupled to hydrogen evolution, have been recorded. The main drawback of hydrogen evolution is the formation of a stagnant layer over the heat exchangers surface, which can limit the ethanol vapour diffusion, thus reducing adsorption condensation rate. (C) 2016 Elsevier Ltd. All rights reserved.}, language = {en} } @inproceedings{SchulzMulski, author = {Schulz, Carsten and Mulski, Steve}, title = {About the Necessity of Flexible Gears}, series = {VDI International Conferences on Gears, October 5-7 2015, M{\"u}nchen}, booktitle = {VDI International Conferences on Gears, October 5-7 2015, M{\"u}nchen}, publisher = {VDI Verlag}, address = {D{\"u}sseldorf}, isbn = {978-3-18-092255-3}, pages = {471 -- 482}, language = {en} } @article{ChatzitakisDawoud, author = {Chatzitakis, Paris and Dawoud, Belal}, title = {An alternative approach towards absorption heat pump working pair screening}, series = {Renewable Energy}, volume = {110}, journal = {Renewable Energy}, publisher = {Pergamon-Elsevier}, organization = {PERGAMON-ELSEVIER SCIENCE LTD}, doi = {10.1016/j.renene.2016.08.014}, pages = {47 -- 58}, abstract = {The successful market penetration of modern absorption heat pumps (AHP) today is critically dependent on their thermodynamic performance as well as other key factors like cost, reliability and inherent safety. Conventional AHPs have a proven record in the first two aspects but crucial shortcomings in the last two. For this reason it has been imperative to search for alternative working pairs that could potentially provide comparable performance while also satisfying the rest of the conditions to the best extent possible. As part of a systematic approach towards this direction, a detailed cycle analysis was performed, utilizing an idealized AHP system containing a real working pair, which enabled the identification of five dimensionless parameters and key thermophysical properties that influence the system's thermodynamic efficiency and the circulation ratio. In order to validate those findings, these parameters were calculated and compared between conventional and alternative AHP refrigerants. It turned out that low molecular weight ratios between absorbent and refrigerant have a beneficial effect on both coefficient of performance and the circulation ratio. Furthermore, both the refrigerant acentric factor and the absorbent vaporization enthalpy shall be minimized to obtain better performance. (C) 2016 Elsevier Ltd. All rights reserved.}, language = {en} } @article{WeberHuberBorchseniusetal.2020, author = {Weber, Felix and Huber, Peter and Borchsenius, Fredrik and Braun, Christian}, title = {Performance of TMDI for Tall Building Damping}, series = {Actuators}, volume = {9}, journal = {Actuators}, number = {4}, publisher = {MPDI}, doi = {10.3390/act9040139}, pages = {1 -- 13}, year = {2020}, abstract = {This study investigates the vibration reduction of tall wind-excited buildings using a tuned mass damper (TMD) with an inerter (TMDI). The performance of the TMDI is computed as a function of the floor to which the inerter is grounded as this parameter strongly influences the vibration reduction of the building and for the case when the inerter is grounded to the earth whereby the absolute acceleration of the corresponding inerter terminal is zero. Simulations are made for broadband and harmonic excitations of the first three bending modes, and the conventional TMD is used as a benchmark. It is found that the inerter performs best when grounded to the earth because, then, the inerter force is in proportion to the absolute acceleration of only the pendulum mass, but not to the relative acceleration of the two inerter terminals, which is demonstrated by the mass matrix. However, if the inerter is grounded to a floor below the pendulum mass, the TMDI only outperforms the TMD if the inerter is grounded to a floor within approximately the first third of the building's height. For the most realistic case, where the inerter is grounded to a floor in the vicinity of the pendulum mass, the TMDI performs far worse than the classical TMD.}, language = {en} } @inproceedings{OttawaRomanoEhrlichetal., author = {Ottawa, Patrycja and Romano, Marco and Ehrlich, Ingo and Wagner, Marcus and Gebbeken, Norbert}, title = {The influence of ondulation in fabric reinforced composites on dynamic properties in a mesoscopic scale}, series = {11. LS-DYNA Forum, 9. - 10. Oktober 2012, Ulm}, booktitle = {11. LS-DYNA Forum, 9. - 10. Oktober 2012, Ulm}, pages = {171 -- 172}, abstract = {Structural mechanic properties of fiber reinforced plastics depend on the single components' properties, namely matrix and fiber [5]. Simple micromechanic homogenization theories reach a limit when a laminate consists of fabric reinforced layers instead of unidirectional layers. The ondulations of warp and fill yarn caused by the textile semi-finished product are the reason why the mesoscopic scale, which is in between the microscopic and the macroscopic scale, has to be taken into account when mechanically characterizing fabric reinforced composites [3]. In this scale a mesomechanic kinematic can be derived analytically. Especially, when considering free damped vibrations of structures the repeated acting of the kinematic correlation significantly affects the damping behaviour to higher values compared to theoretically predicted damping ratios. The model is investigated using Finite-Element-Analyses and basically validated experimentally.}, language = {en} } @article{KofianiNonnWierzbicki, author = {Kofiani, Kirki and Nonn, Aida and Wierzbicki, Tomasz}, title = {New calibration method for high and low triaxiality and validation on SENT specimens of API X70}, series = {International Journal of Pressure Vessels and Piping}, volume = {111-112}, journal = {International Journal of Pressure Vessels and Piping}, doi = {10.1016/j.ijpvp.2013.07.004}, pages = {187 -- 201}, abstract = {The determination of the exact mechanical properties of material is essential for an optimal and safe design of linepipes. It is especially important for the prevention of over-engineering and the reliable assessment of complex accidental loading, such as extreme bending due to loss of buoyancy of support, or abrupt ground movement. Currently, the focus of research in offshore deepwater installations and linepipes is towards pre-cracked structures with high triaxiality stress states and complex loading histories. At the same time, low triaxiality stress states must be correctly studied in order to represent shear dominated failure in pipes. A comprehensive experimental and numerical program was undertaken to determine the mechanical properties of the traditional API X70 grade of steel. The material was characterized for anisotropic plasticity, fracture initiation and uncracked ductility for various states of stress. The same material was also used for pre-cracked fracture toughness assessment. The experimental program included flat and round specimens. The first type of tests on flat butterfly-shaped, central hole, notched and circular disk specimens; were selected to address the low stress triaxiality range. Tests on round notched bar specimens and SENT fracture mechanics tests extended the characterization and verification process to higher stress triaxiality values. This program covered a wide range of stress conditions and demonstrated their effect on the material resistance to crack extension. Each test conducted was numerically simulated using solid finite element models, matching the exact geometric and loading history features. The numerical simulation provided information on the local stress and strain fields around the location of the potential or existing cracks. Based on the above hybrid experimental/numerical technique tailored for pipe applications, the MMC fracture model was calibrated. The model relates the material ductility not only to stress triaxiality but also to the Lode parameter. The predictive capabilities of the MMC were then evaluated in the case of SENT testing, used extensively in the pipeline industry. It was shown that the present fracture model calibration can describe fracture behavior of SENT experiments.}, language = {en} } @article{KeimParedesNonnetal., author = {Keim, Vincent and Paredes, Marcelo and Nonn, Aida and M{\"u}nstermann, Sebastian}, title = {FSI-simulation of ductile fracture propagation and arrest in pipelines}, series = {International Journal of Pressure Vessels and Piping}, volume = {182}, journal = {International Journal of Pressure Vessels and Piping}, number = {May}, publisher = {Elsevier}, doi = {10.1016/j.ijpvp.2020.104067}, abstract = {The fracture propagation and arrest control for pipelines transporting rich natural gases and high vapor pressure liquids is based on the Battelle Two-Curve Model (BTCM). Distinct limitations of this model were demonstrated for past and modern steels and gas mixtures. These can be related to the insufficient description of individual physical processes and interactions between the pipe material and transported mixture during the running ductile fracture. In the past, fluid-structure interaction (FSI) models enabled a more sophisticated, coupled analysis of the failure scenario. To quantify their capability of describing the multi-physical processes, the FSI models need to be verified by experimental data from full-scale burst tests (FSBT). Therefore, this paper deals with the simulation of five FSBTs from the literature on API grade X65 pipes with different pipe geometries, mixtures and initial conditions. The FSI is modeled by the coupled Euler-Lagrange (CEL) method. The modified Mohr-Coulomb (MMC) model is implemented in the CEL framework to describe the deformation and ductile fracture in the X65/L450 pipes. 3D Euler equations are used to calculate the mixture decompression with the GERG-2008 equation of state defining the volumetric behavior of a CO2-rich mixture, CH4 and H2. The extended model considers the effect of soil backfill on the pipe deformation and inertia. The numerical predictions agree well with the experimental findings in terms of the crack propagation speed and arrest length underlining the capability of the developed numerical tool.}, subject = {Bruchmechanik}, language = {en} } @phdthesis{Romano, author = {Romano, Marco}, title = {Charakterisierung von gewebeverst{\"a}rkten Einzellagen aus kohlenstofffaserverst{\"a}rktem Kunststoff (CFK) mit Hilfe einer mesomechanischen Kinematik sowie strukturdynamischen Versuchen}, publisher = {Shaker}, address = {Aachen}, isbn = {978-3-8440-5177-3}, doi = {10.2370/9783844051773}, pages = {254}, abstract = {Die vorliegende Arbeit behandelt die analytische und numerische Identifikation einer mesomechanischen Kinematik in gewebeverst{\"a}rkten Einzellagen sowie deren Validierung {\"u}ber die Strukturdynamik von flachen stabf{\"o}rmigen Probek{\"o}rpern aus kohlenstofffaserverst{\"a}rktem Kunststoff (CFK). Unter der Voraussetzung, dass das wiederholte Wirken der Kinematik Energie dissipiert, tr{\"a}gt sie bei zyklischer viskoelastischer Deformation zus{\"a}tzlich zur reinen viskoelastischen Werkstoffd{\"a}mpfung in gewebeverst{\"a}rkten Einzellagen bei. Die analytischen und numerischen Untersuchungen beschr{\"a}nken sich auf die Betrachtung des ebenen, zweidimensionalen Zusammenhangs einer vollst{\"a}ndigen Ondulation bzw. einer repr{\"a}sentativen Sequenz in Dickenrichtung. Zur Parameteridentifikation werden die geometrischen Abmessungen in definierten Schritten variiert. Daf{\"u}r wird der Grad der Ondulation in gewebeverst{\"a}rkten Einzellagen {\~O}=A/L als dimensionslose Kennzahl eingef{\"u}hrt. Zur Validierung der d{\"a}mpfungserh{\"o}henden Wirkung der in den analytischen und numerischen Untersuchung identifizierten mesomechanischen Kinematik in gewebeverst{\"a}rkten Einzellagen werden in experimentellen strukturdynamischen Untersuchungen frei abklingende Transversalschwingungen von einseitig fest eingespannten Probek{\"o}rpern untersucht. Im Detail werden flache stabf{\"o}rmige Probek{\"o}rper aus kohlenstofffaserverst{\"a}rktem Epoxidharz mit Lagenaufbauten aus 0°-unidirektionalen und gewebeverst{\"a}rkten Einzellagen untersucht. Die Ergebnisse der experimentellen strukturdynamischen Untersuchungen dienen schließlich der Validierung des analytischen Modells und der numerischen Berechnungen. Die d{\"a}mpfungserh{\"o}hende Wirkung der identifizierten mesomechanischen Kinematik wird schließlich in Abh{\"a}ngigkeit des eingef{\"u}hrten Grades der Ondulation {\~O} quantifiziert.}, language = {de} } @article{NonnDahlBleck, author = {Nonn, Aida and Dahl, Winfried and Bleck, Wolfgang Peter}, title = {Numerical modelling of damage behaviour of laser-hybrid welds}, series = {Engineering Fracture Mechanics}, volume = {75}, journal = {Engineering Fracture Mechanics}, doi = {10.1016/j.engfracmech.2007.10.015}, pages = {3251 -- 3263}, abstract = {The effect of laser-hybrid welds on deformation and failure behaviour of fracture mechanics specimens is investigated in order to provide quantitative prediction of damage tolerance and residual strength. The simulation of crack initiation and crack extension in hybrid welds is performed by applying GTN damage model. The identification of damage parameters requires combined numerical and experimental analyses. The tendency to crack path deviation during crack growth depends strongly on the constraint development at the interface between base and weld metal. In order to quantify the influence of local stress state on the crack path deviation, the initial crack location is varied. Finally, the results from fracture mechanics tests are compared to real component, beam-column-connection, with respect to fracture resistance.}, language = {en} } @inproceedings{NonnCerroneStallybrassetal., author = {Nonn, Aida and Cerrone, Albert R. and Stallybrass, C. and Meuser, H.}, title = {Microstructure-based modeling of high-strength linepipe steels}, series = {6th Pipeline Technology Conference 2013, 6-9 October, Ostend, Belgium}, booktitle = {6th Pipeline Technology Conference 2013, 6-9 October, Ostend, Belgium}, doi = {10.13140/2.1.2797.4404}, abstract = {HE MODERN LONGITUDINALLY WELDED pipes with new generation of steel materials exhibit excellent mechanical properties due to the continuous improvements in thermomechanical controlled processing of plates (TMCP) and pipe (UOE) production processes. While the adjustment of process parameters allows for optimized design of microstructure, safe installation and operation of these pipes for long distance, gas transmission pipelines require a detailed knowledge and characterization of their deformation and fracture performance for specific application. Although the influence of texture on the material properties can be qualitatively estimated, a quantitative link between the microstructural constituents and mechanical behavior is still missing. This paper aims to present the procedure for the development of microstructure-based model to quantitatively describe the mechanical behavior of bainitic X80 pipeline steel. In the first step, the metallographic analysis is conducted to identify the microstructural characteristics, such as volume fractions of microstructure constituents (granular and lower bainite, M-A phase) and their distributions. The strength properties in terms of flow curves are determined by tensile tests on mini-flat and round bar specimens with different sizes. Subsequently, a 2D three-phase model is developed based on the results from the quantitative analyses of microstructure with each phase modeled using the von-Mises plasticity theory. The flow curves of single phases are estimated by considering experimental findings, the chemical composition and microstructural description of each phase. This 2D FE model is then applied to predict ielding and hardening behavior. In addition to the 2D three-phase model, a 3D two-phase model is developed for the purposes of exploring the viability of using a spectral solver to analyze X80 synthetic microstructures. Here, the FFT-based approach is compared against the crystal-plastic finite-element method. The results contribute to a better understanding of the mechanical behavior and allow a more precise microstructure design of the bainitic steels.}, language = {en} } @inproceedings{NonnKalwa, author = {Nonn, Aida and Kalwa, Christoph}, title = {Analysis of dynamic ductile fracture propagation in pipeline steels}, series = {6th Pipeline Technology Conference (2013), Ostend, Belgium}, booktitle = {6th Pipeline Technology Conference (2013), Ostend, Belgium}, doi = {10.13140/2.1.4370.3046}, abstract = {Analysis of dynamic ductile fracture propagation in pipeline steels: a damage-T IS A WELL-ESTABLISHED fact that the successful application of new generation of high-strength steel grades for long-distance gas transmission depends strongly on full understanding and appropriate characterization of fracture resistance. A damage mechanics approach has found to be a very promising tool in supporting the experimental characterization of ductile fracture propagation. The major advantage of this approach lies in the consideration of the influence of local stress and strain variables on the damage evolution and thus its capability to describe the fracture resistance of the pipelines with different stress triaxiality level by using the same set of parameters. However, the wider application of this approach has been limited due to the issues such as reliable determination of input parameters and required material properties, mesh size dependence, etc.. The objective of this paper is to characterize dynamic ductile fracture resistance of X65 and X80 pipeline materials and to demonstrate the potential of damage mechanics approach for the simulation of dynamic fracture propagation by using two damage models: (1) Cohesive Zone (CZ) model and (2) Gurson-Tvergaard-Needleman (GTN) model. In the first step, results from quasi-static and dynamic tensile tests are used to describe plasticity in terms of flow curves. The calibration of input parameters for both models is performed by using the load-deformation curves from quasi-static tests on non-standard drop-weight tear (DWT) specimens with pre-fatigued crack. b. In the next step, estimated damage model parameters are verified by means of the dynamic tests on the pressed and Chevron notch DWT specimens. Different amounts of crack growth are established by varying the drop height. The experimental fracture resistance is quantified in terms of J-integral at specific crack length. The numerical results are evaluated with respect to global load-deformation and fracture resistance behavior. Furthermore, damage simulations are applied for quantification of local stress conditions in order to identify the major factors controlling the crack propagation. The results reported here serve as a basis for better understanding of fracture performance in dependences of geometry and material properties.}, language = {en} } @inproceedings{NonnKalwa, author = {Nonn, Aida and Kalwa, Christoph}, title = {Failure modeling of pipeline X100 Material in temperature transition region}, series = {22nd International Society of Offshore and Polar Engineering 2012 (ISOPE 2012), Rhodes, Greece}, booktitle = {22nd International Society of Offshore and Polar Engineering 2012 (ISOPE 2012), Rhodes, Greece}, abstract = {This paper focuses on the characterization of the fracture performance of X100 material in transition temperature region using both experimental and numerical methods. The ductile fracture has been analyzed using tests on round notched bar specimens and standard fracture mechanics tests performed at room temperature. In previous publications the damage model Gurson-Tvergaard-Needleman (GTN) has been applied and verified by existing experimental data to describe ductile fracture behavior. The brittle fracture and the fracture in temperature transition region have been studied by means of deep and shallow notched SENB specimens at two different temperatures T=- 80°C and -40°C. Besides elastic-plastic analyses to quantify constraint levels for different initial crack configurations at the onset of cleavage fracture, the brittle failure has been described using modified Beremin model. The influence of the stable crack growth on the cleavage failure probability in temperature transition region has been captured by coupling the ductile fracture model (GTN) with the modified Beremin model. Finally, examples have been presented for the practical application of the numerical results on the fracture assessment of the flawed high-strength pipelines.}, language = {en} } @inproceedings{NonnKalwa, author = {Nonn, Aida and Kalwa, Christoph}, title = {The effect of microstructure, strain hardening and strain rate on the fracture behavior of high strength pipeline steels}, series = {2nd International Conference on Material Modelling (ICMM2), 31th August - 2nd September, 2011 at Mines Paris Tech, France}, booktitle = {2nd International Conference on Material Modelling (ICMM2), 31th August - 2nd September, 2011 at Mines Paris Tech, France}, language = {en} } @inproceedings{NonnVoelling, author = {Nonn, Aida and V{\"o}lling, Alexander}, title = {Lokale Spannungsanalyse bei Rissinitiierung}, series = {4. Workshop Kompetenzverbund Kerntechnik "Komponentensicherheit und Werkstoffverhalten", MPA Stuttgart, Germany}, booktitle = {4. Workshop Kompetenzverbund Kerntechnik "Komponentensicherheit und Werkstoffverhalten", MPA Stuttgart, Germany}, subject = {Rissverhalten}, language = {en} } @inproceedings{NonnKalwa, author = {Nonn, Aida and Kalwa, Christoph}, title = {Application of probabilistic fracture mechanics for safety assessment of longitudinally welded linepipes}, series = {6th Pipeline Technology Conference (2013), Ostend, Belgium}, booktitle = {6th Pipeline Technology Conference (2013), Ostend, Belgium}, language = {en} } @inproceedings{NonnKalwa, author = {Nonn, Aida and Kalwa, Christoph}, title = {Application of damage mechanics approach for crack propagation in pipeline}, series = {19th Biennial Joint Technical Meeting (JTM) on Pipeline Research, April 29 - May 3, 2013, Sydney, Australia}, booktitle = {19th Biennial Joint Technical Meeting (JTM) on Pipeline Research, April 29 - May 3, 2013, Sydney, Australia}, language = {en} } @inproceedings{NonnErdelenPepplerWesseletal., author = {Nonn, Aida and Erdelen-Peppler, Marion and Wessel, Waldemar and Mahn, Denise}, title = {How reliable are the current testing procedures for the safety assurance against crack propagation in seamless gas pipelines}, series = {Proceedings of the ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering (OMAE2014), Volume 4A: Structures, Safety and Reliability, June 8-13, 2014, San Francisco, USA}, booktitle = {Proceedings of the ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering (OMAE2014), Volume 4A: Structures, Safety and Reliability, June 8-13, 2014, San Francisco, USA}, doi = {10.13140/2.1.3190.6567}, abstract = {The worldwide growing energy demand with the exploration of new gas fields has promoted the development of high toughness seamless pipeline steels which should sustain the increasing demands resulting from the complex loading situations. One of the most important prerequisites for safe installation and operation of long distance gas transmission pipelines is the detailed knowledge and characterization of their fracture performance for specific applications. However, recent industry experience has revealed concerns related to the limitations and reliability of current test methods for brittle-to-ductile transition evaluation. Regarding the transition temperature evaluation, the critical issues involve Drop-Weight Tear Testing (DWTT) and full-scale West-Jefferson (WJ) test applied to the smaller pipes with diameter less than 500mm. The DWTT leads frequently to invalid results in terms of abnormal fracture appearance and inverse fracture occurrence. It is still not clear if this behavior is only owed to a testing effect, which material characteristics cause it and how far it reflects the full-scale behavior. Similar observations were made for the West-Jefferson tests, which could not be assessed in the standard manner either. Again, the question was towards testing effects and the behavior of the pipeline transporting gaseous media remains unanswered. Therefore, this paper aims at identifying open questions on basis of a literature study and own experimental results and showing possible ways forward in demonstrating safety in design against propagating fracture.}, language = {en} } @inproceedings{NonnWesselSchmidt, author = {Nonn, Aida and Wessel, Waldemar and Schmidt, Tanja}, title = {Application of finite element analysis for assessment of fracture behavior of modern high toughness seamless pipeline steels}, series = {23rd International Society of Offshore and Polar Engineering 2013 (ISOPE 2013), Anchorage, USA}, booktitle = {23rd International Society of Offshore and Polar Engineering 2013 (ISOPE 2013), Anchorage, USA}, doi = {10.13140/2.1.4239.2322}, abstract = {Fracture behavior of seamless pipeline material X65Q acc. to API 5L has been studied both experimentally and numerically at different loading conditions (quasi-static vs. dynamic) and temperatures. The recent findings have shown difficulties in applying well established methods for determination of transition behavior or prediction of ductile crack arrest for the new generation of high-toughness steels. The irregular fracture performance (e.g. so-called "abnormal inverse fracture" appearance, significant scattering in ductile-to-brittle-transition-temperature region, etc.) suggests that the influence of pipe dimensions, loading parameters, crack initiation resistance as well as testing procedure on the fracture behavior has been neither understood nor properly described. This work aims to shed light on these questions regarding the applicability of conventional methods and to better illuminate most relevant parameters affecting fracture behavior of high toughness steels. To achieve this goal, experimental data basis for analysis of fracture behavior in transition and upper shelf regime has been established by conducting quasi-static fracture mechanics tests and dynamic tests on Battelle Drop Weight Tear (BDWT or DWT) specimens at different temperatures. The evaluation of obtained test results in upper shelf has been additionally complemented by numerical simulation of damage behavior. The results highlight the influence of stress conditions on fracture behavior with reference to pipe dimensions and loading conditions and, subsequently, may be used as a basis for revision of existing design methods.}, subject = {Rissfortschritt}, language = {en} } @inproceedings{NonnBrauer, author = {Nonn, Aida and Brauer, Holger}, title = {Establishing the correlation between impact energies for different sized specimens using damage models}, series = {Proceedings of the 10th International Pipeline Conference 2014 (IPC2014), September 29 - October 3, 2014, Calgary, Alberta, Canada, Vol. 3: Materials and joining, risk and reliability}, booktitle = {Proceedings of the 10th International Pipeline Conference 2014 (IPC2014), September 29 - October 3, 2014, Calgary, Alberta, Canada, Vol. 3: Materials and joining, risk and reliability}, doi = {10.1115/IPC2014-33164}, abstract = {The safety assessment of flawed pressurized pipes requires the knowledge of toughness properties which are usually provided in terms of impact energy from standard full-sized CVN notch specimens. For pipes with wall thickness less than 10mm different Charpy standards allow for the application of sub-sized specimens. However, it is still not fully clear how the impact energy from sub-sized specimens can be used to evaluate the fracture resistance of the pipes and how this energy correlates to the one from the full-sized specimen. Although different empirical correlations between sub-sized and full-sized specimens exist in the literature their validity is questionable since they are based on the results for older generation of steels. In the recent years the application of damage mechanics models has been promoted to assess the fracture behavior and deformation capacity of pipelines. The main advantage of these models can be found in their capability to link the damage evolution and the underlying stress/strain condition. In this paper damage mechanics approach is applied to describe fracture behavior of X65 pipeline material. Within the damage mechanics approach, Gurson-Tvergaard-Needleman (GTN) model is considered to be adequate for the simulation of ductile fracture. For brittle fracture, GTN model is extended by a propagation criterion which examines if the cleavage fracture stress is reached by the maximal principal stresses. The model parameters are calibrated and verified by means of load-displacement curves obtained from instrumented impact tests on different sized CVN specimens. This damage model is subsequently employed to simulate ductile-brittle transition behavior.}, language = {en} } @inproceedings{NonnParedesKeimetal., author = {Nonn, Aida and Paredes, Marcelo and Keim, Vincent and Wierzbicki, Tomasz}, title = {Comparison of Fracture Models to Quantify the Effects of Material Plasticity on the Ductile Fracture Propagation in Pipelines}, series = {Proceedings of the 2018 12th International Pipeline Conference, Volume 3: Operations, Monitoring, and Maintenance, Materials and Joining, September 24-28, 2018, Calgary, Alberta, Canada}, booktitle = {Proceedings of the 2018 12th International Pipeline Conference, Volume 3: Operations, Monitoring, and Maintenance, Materials and Joining, September 24-28, 2018, Calgary, Alberta, Canada}, doi = {10.1115/IPC2018-78366}, abstract = {Various numerical approaches have been developed in the last years aimed to simulate the ductile fracture propagation in pipelines transporting CO2 or natural gas. However, a reliable quantification of the influence of material plasticity on the fracture resistance is still missing. Therefore, more accurate description of the material plasticity on the ductile fracture propagation is required based on a suitable numerical methodology. In this study, different plasticity and fracture models are compared regarding the ductile fracture propagation in X100 pipeline steel with the objective to quantify the influence of plasticity parameters on the fracture resistance. The plastic behavior of the investigated material is considered by the quadratic yield surface in conjunction with a non-associated quadratic plastic flow potential. The strain hardening can be appropriately described by the mixed Swift-Voce law. The simulations of ductile fracture are conducted by an uncoupled, modified Mohr-Coulomb (MMC) and the micromechanically based Gurson-Tvergaard-Needleman (GTN) models. In contract to the original GTN model, the MMC model is capable of describing ductile failure over wide range of stress states. Thus, ductile fracture resistance can be estimated for various load and fracture scenarios. Both models are used for the simulation of fracture propagation in DWTT and 3D pressurized pipe sections. The results from the present work can serve as a basis for establishing the correlation between plasticity parameters and ductile fracture propagation.}, language = {en} } @inproceedings{NonnErdelenPepplerWesseletal., author = {Nonn, Aida and Erdelen-Peppler, Marion and Wessel, Waldemar and Harksen, Silke and Mahn, Denise}, title = {How to assure fracture-propagation control for seamless gas pipelines?}, series = {Proceedings of the 2014 10th International Pipeline Conference (IPC2014), Volume 3: Operations, Monitoring, and Maintenance, Materials and Joining, September 29-October 3, 2014, Calgary, Canada}, booktitle = {Proceedings of the 2014 10th International Pipeline Conference (IPC2014), Volume 3: Operations, Monitoring, and Maintenance, Materials and Joining, September 29-October 3, 2014, Calgary, Canada}, doi = {10.1115/IPC2014-33169}, abstract = {Fracture propagation control in gas transmission gas pipelines belongs to the major design requirements for safe operation at high internal pressures. However, the current tests such as Drop-Weight-Tear Test (DWTT) and full-scale West-Jefferson (WJ) test reach the limits of their applicability with respect to transition temperature evaluation for seamless quenched and tempered small diameter pipes reflecting nowadays alloying concepts related to mechanical properties. Hereby, different geometry and material effects are evident which might lead to misinterpretation and unreliability of testing results. This paper aims to discuss open issues addressed in the literature and in own experimental findings with respect to reliability and transferability of testing methods, fracture parameters and their representativeness of seamless quenched and tempered pipeline behavior. By applying damage mechanics approach, it is possible to quantify the prevailing stress state and thus to understand the mechanisms controlling specific fracture appearance (ductile or brittle). Furthermore, studies were performed with objective to quantify the effect of different parameters (geometry, material and loading) on the fracture performance of the pipeline. The results from these investigations will serve as a basis for a safe pipeline design against propagating fracture.}, language = {en} } @inproceedings{NonnParedesNordhagenetal., author = {Nonn, Aida and Paredes, Marcelo and Nordhagen, H. O. and Munkejord, S. T. and Wierzbicki, Tomasz}, title = {Challenges in fluid-structure modeling of crack propagation and arrest in modern steel pipelines}, series = {14th International Congress on Fracture (ICF14), 18-23 June 2017, Rhodes, Greece}, booktitle = {14th International Congress on Fracture (ICF14), 18-23 June 2017, Rhodes, Greece}, pages = {1351 -- 1352}, language = {en} } @inproceedings{KarbasianGrossWeegeNonnetal., author = {Karbasian, H. and Groß-Weege, J. and Nonn, Aida and Zimmermann, S. and Kalwa, Christoph}, title = {Assessment of collapse resistance of UOE pipes - comparison of full-scale and ring collapse tests}, series = {Proceedings of the 10th International Pipeline Conference 2014 (IPC 2014), September 29 - October 3, 2014, Calgary, Alberta, Canada}, booktitle = {Proceedings of the 10th International Pipeline Conference 2014 (IPC 2014), September 29 - October 3, 2014, Calgary, Alberta, Canada}, language = {en} } @inproceedings{NonnDahlBleck, author = {Nonn, Aida and Dahl, Winfried and Bleck, Wolfgang Peter}, title = {Damage Modelling and Safety Assessment of the Hybrid Welded Structures}, series = {5th German-Japanese Seminar "Materials, Processes and Components", Fraunhofer Institute for Mechanics of Materials, Freiburg, Germany}, booktitle = {5th German-Japanese Seminar "Materials, Processes and Components", Fraunhofer Institute for Mechanics of Materials, Freiburg, Germany}, language = {en} } @inproceedings{NonnKalwa, author = {Nonn, Aida and Kalwa, Christoph}, title = {Modeling of damage behavior of high strength pipeline steel}, series = {18th European Conference on Fractur: Fracture of Materials and Structures from Micro to Macro Scale, August 30 - September 03, 2010, Dresden, Germany}, booktitle = {18th European Conference on Fractur: Fracture of Materials and Structures from Micro to Macro Scale, August 30 - September 03, 2010, Dresden, Germany}, language = {en} } @inproceedings{Nonn, author = {Nonn, Aida}, title = {Failure modeling of hybrid-laser welds in transition temperature region}, series = {18th European Conference on Fracture, Fracture of Materials and Structures from Micro to Macro Scale, August 30 - September 03, 2010 Dresden, Germany}, booktitle = {18th European Conference on Fracture, Fracture of Materials and Structures from Micro to Macro Scale, August 30 - September 03, 2010 Dresden, Germany}, address = {Dresden}, language = {en} } @article{BohmannSchlampEhrlich, author = {Bohmann, T. and Schlamp, Matthias and Ehrlich, Ingo}, title = {Acoustic emission of material damages in glass fibre-reinforced plastics}, series = {Composites Part B: Engineering}, volume = {155}, journal = {Composites Part B: Engineering}, number = {December}, publisher = {Elsevier}, doi = {10.1016/j.compositesb.2018.09.018}, pages = {444 -- 451}, abstract = {The aim of this study is to compare two different standardized testing procedures, tensile testing and Mode-I double cantilever beam (DCB) testing, to evaluate a possible correlation between the dominant failure in glass fibre-reinforced plastics and their according acoustic emissions (AE). AE is processed by using a burst collection of all recorded transient signals and is further analysed with the k-means clustering algorithm. To generate damage related AE, a series of experiments for tensile testing and Mode-I DCB testing is performed on 16-layer glass fibre/epoxy specimens with a cross-ply lay-up for tensile and an unidirectional lay-up for Mode-I DCB testing. Three sensors at tensile testing and one sensor at Mode-I DCB testing gather AE data. The results of clustered burst signals show a good accordance between both testing procedures, with a similar weighted peak frequency (WPF) range in each classified cluster. In total, three different clusters are determined. An assignment of these three clusters to the three dominant damage mechanisms, visually observed by microscopy, is suggested.}, language = {en} } @techreport{ValentinoRomanoEhrlichetal., author = {Valentino, Piergiorgio and Romano, Marco and Ehrlich, Ingo and Furgiuele, Franco and Gebbeken, Norbert}, title = {Mechanische Charakterisierung von basaltfaser-verst{\"a}rkten Kunststoffen mit Gewebeverst{\"a}rkung - Numerische und experimentelle Untersuchungen}, series = {Forschungsbericht 2013}, journal = {Forschungsbericht 2013}, publisher = {inixmedia GmbH Marketing \& Medienberatung}, organization = {Ostbayerische Technische Hochschule Regensburg}, language = {de} } @inproceedings{Afanasev, author = {Afanasev, Anna}, title = {Force-oriented 3D printing of continuous fiber-reinforced plastic structures}, series = {Applied Research Conference 2019 - ARC 2019, 08 July 2019, Regensburg}, booktitle = {Applied Research Conference 2019 - ARC 2019, 08 July 2019, Regensburg}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus}, publisher = {Pro Business GmbH}, address = {Berlin}, isbn = {978-3-96409-182-6}, pages = {213 -- 218}, subject = {Faserverbundwerkstoff}, language = {en} } @inproceedings{BaumerKastenmeierEhrlich, author = {Baumer, A. and Kastenmeier, Andreas and Ehrlich, Ingo}, title = {Investigation of Bolted Composite Joints with Different Reinforcement Elements at the Bolt Hole}, series = {4th Applied Research Conference, 5th July 2014, Ingolstadt}, booktitle = {4th Applied Research Conference, 5th July 2014, Ingolstadt}, editor = {Ziemann, Olaf and Mottok, J{\"u}rgen and Pforr, Johannes}, publisher = {Shaker}, pages = {255 -- 258}, language = {en} } @inproceedings{FritzSchmidEhrlich, author = {Fritz, B. and Schmid, Vinzent and Ehrlich, Ingo}, title = {Analytical and numerical shear stress analysis of adhesive structural bonded joints under tension load}, series = {Applied Research Conference 2014 - ARC 2014, 5th July 2014, Ingolstadt}, booktitle = {Applied Research Conference 2014 - ARC 2014, 5th July 2014, Ingolstadt}, editor = {Ziemann, Olaf and Mottok, J{\"u}rgen and Pforr, Johannes}, publisher = {Shaker}, address = {Aachen}, pages = {266 -- 271}, language = {de} } @inproceedings{BaumerKastenmeierEhrlich, author = {Baumer, A. and Kastenmeier, Andreas and Ehrlich, Ingo}, title = {A Numerical Study of Reinforced Bolted Composite Joints}, series = {Applied Research Conference 2015: ARC 2015 - N{\"u}rnberg, 3rd July 2015}, booktitle = {Applied Research Conference 2015: ARC 2015 - N{\"u}rnberg, 3rd July 2015}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Scharfenberg, J. and Ziemann, Olaf}, publisher = {Book-on-demand-Verlag}, pages = {278 -- 282}, language = {en} } @inproceedings{WaetzigSchmidEhrlich, author = {W{\"a}tzig, A. and Schmid, Vinzent and Ehrlich, Ingo}, title = {Damage Modelling of Adhesive Joints Using the Cohesive Zone Model}, series = {Applied Research Conference 2016 - ARC 2016, Augsburg, 24 June 2016}, booktitle = {Applied Research Conference 2016 - ARC 2016, Augsburg, 24 June 2016}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Stolle, Reinhard}, publisher = {Pro Business Verlag}, address = {Berlin}, language = {en} } @inproceedings{DinnebierEhrlich, author = {Dinnebier, Heinrich and Ehrlich, Ingo}, title = {The Effects of Severe Temperature Changes and High Humidity on Porous CFRP}, series = {Proceedings of the 15th International Materials Symposium (IMSP´2014), Pamukkale University (Denizli, Turkey), 15./17. October 2014}, booktitle = {Proceedings of the 15th International Materials Symposium (IMSP´2014), Pamukkale University (Denizli, Turkey), 15./17. October 2014}, editor = {Meran, C.}, pages = {433 -- 440}, abstract = {Purpose: A route to manufacture porous carbon fiber reinforced plastic (CFRP) for study purposes is described. Design/methodology/approach: The porous CFRP is characterized using standard techniques such as matrix digestion as well as the more sophisticated method of high resolution Microfocus X-Ray Tomography (μCT). A comparison of the results of those methods is presented. The mass gains of specimens with a wide range of porosity have been measured both in constant humidity and in alternating environments. Findings: It could be shown that severe temperature changes can temporarily increase the moisture content of porous CFRP. However, after the return to a constant environment, the moisture content returns back to saturation levels. Furthermore, it could be shown by X-Ray Tomography that even under severe climatic conditions no permanent liquid water condensates inside the pores. Research limitations/implications: Using Microfocus Computed Tomography it could be shown that even after nearly a year under hot-wet conditions and more than 150 severe temperature cycles there is no liquid water detectable inside the pores. Originality/value: In this paper the effects of severe temperature changes and high humidity on porous CFRP.}, language = {en} } @inproceedings{EhrlichDinnebierJost, author = {Ehrlich, Ingo and Dinnebier, Heinrich and Jost, C.}, title = {Comparison of Impact Delaminations in CFRP Using Ultrasonic Testing, Microfocus Computed X-Ray Tomography and Micrographic Cross-Section}, series = {Proceeding of the 15th International Materials Symposium (IMSP´2014), Pamukkale University (Denizli, Turkey), 15./17. October 2014}, booktitle = {Proceeding of the 15th International Materials Symposium (IMSP´2014), Pamukkale University (Denizli, Turkey), 15./17. October 2014}, editor = {Meran, C.}, pages = {441 -- 450}, language = {en} } @inproceedings{Wenzl, author = {Wenzl, C.}, title = {Comparison of Analytical and Numerical Results for the Deformation of Circular Curved Structures under Pressure Load}, series = {Applied Research Conference 2018 - ARC 2018, 10 July 2018 Deggendorf}, booktitle = {Applied Research Conference 2018 - ARC 2018, 10 July 2018 Deggendorf}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Bogner, Werner}, publisher = {Pro Business GmbH}, address = {Berlin}, isbn = {978-3-96409-018-8}, pages = {150 -- 155}, language = {en} } @inproceedings{FaberKastenmeierEhrlich, author = {Faber, M. and Kastenmeier, Andreas and Ehrlich, Ingo}, title = {Three-dimensional finite element analysis of a composite tube with multi-row bolted joints}, series = {Applied Research Conference 2016 - ARC 2016, Augsburg, 24 June 2016}, booktitle = {Applied Research Conference 2016 - ARC 2016, Augsburg, 24 June 2016}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Stolle, Reinhard}, publisher = {Pro Business Verlag}, address = {Berlin}, language = {de} } @inproceedings{Gebhardt, author = {Gebhardt, Jakob}, title = {Low Velocity Impact of GFRP Laminate - Experimental Observations and Numerical Modelling}, series = {Applied Research Conference 2018 - ARC 2018, 10 July 2018 Deggendorf}, booktitle = {Applied Research Conference 2018 - ARC 2018, 10 July 2018 Deggendorf}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Bogner, Werner}, publisher = {Pro Business GmbH}, address = {Berlin}, isbn = {978-3-96409-018-8}, pages = {211 -- 215}, language = {en} } @inproceedings{IbanezGomezKastenmeierEhrlich, author = {Ibanez Gomez, D. and Kastenmeier, Andreas and Ehrlich, Ingo}, title = {Development and construction of a winding machine for the production of composite tubes}, series = {4th Applied Research Conference - ARC 2014, 5th July 2014, Ingolstadt}, booktitle = {4th Applied Research Conference - ARC 2014, 5th July 2014, Ingolstadt}, editor = {Ziemann, Olaf and Mottok, J{\"u}rgen and Pforr, Johannes}, publisher = {Shaker}, address = {Aachen}, pages = {315 -- 318}, language = {en} } @inproceedings{BrulandSchmidEhrlich, author = {Bruland, Matthias and Schmid, Vinzent and Ehrlich, Ingo}, title = {Analyzing and Testing of a Single Solution of Self-cutting Thread Inserts in Composites}, series = {Applied Research Conference 2014 - ARC 2014, 5th July 2014, Ingolstadt}, booktitle = {Applied Research Conference 2014 - ARC 2014, 5th July 2014, Ingolstadt}, editor = {Ziemann, Olaf and Mottok, J{\"u}rgen and Pforr, Johannes}, publisher = {Shaker}, pages = {286 -- 288}, language = {en} } @article{SchimmerLadewigMotschetal., author = {Schimmer, Florian and Ladewig, Sven and Motsch, Nicole and Hausmann, Joachim M. and Ehrlich, Ingo}, title = {Comparison of Low-Velocity Impact Damage Behavior of Unidirectional Carbon Fiber-Reinforced Thermoset and Thermoplastic Composites}, series = {Key Engineering Materials}, volume = {809}, journal = {Key Engineering Materials}, publisher = {Trans Tech Publications}, issn = {1662-9795}, doi = {10.4028/www.scientific.net/KEM.809.9}, pages = {9 -- 14}, abstract = {This paper investigates the damage behavior of thermoset and thermoplastic fiber-reinforced composites. The specimens were subjected to low-velocity impacts (LVI) to produce barely visible impact damages (BVID). To compare the dependency of the matrix system and the laminate lay-up on the impact damage, four test series were set up. Therefore, laminates with an epoxy (EP) and a polyether ether ketone (PEEK) matrix in a quasi-isotropic (QI) [+45/0/-45/90]2s and an orthotropic (OT) fiber lay-up [0/90]4s were manufactured. To eliminate the influence of variant fiber systems, the thermoplastic tape and the thermoset prepreg contain similar carbon fibers (CF). After impact testing with three different impact energies, inner damages were investigated by using ultrasonic analyses. To get a deeper understanding of the interior damage mechanisms, cross sections of the damaged areas were examined via reflected light microscopy. By using these destructive and non-destructive test methods, significant differences in the damage behavior of composites with thermoplastic and thermoset matrix systems were identified for both laminate lay-ups.}, language = {en} } @inproceedings{SieglRiegerKovariketal., author = {Siegl, Marco and Rieger, David and Kov{\´a}r{\´i}k, Tom{\´a}š and Ehrlich, Ingo}, title = {Long-Term Behavior of Thermoplastics under UV Light tested by a self-build Device}, series = {3. OTH-Clusterkonferenz, 13. April 2018, Weiden, Tagungsband; Festschrift, 5 Jahre OTH-Verbund}, booktitle = {3. OTH-Clusterkonferenz, 13. April 2018, Weiden, Tagungsband; Festschrift, 5 Jahre OTH-Verbund}, organization = {Ostbayerische Technische Hochschule}, pages = {118 -- 122}, abstract = {This article presents first results of artificial aging experi-ments by ultraviolet (UV) irradiation on thermoplasticmaterials conducted as an intent of the research project Thermoplastic Composite Structures (TheCoS) in colla-boration of the Ostbayerische Technische Hochschule(OTH) Regensburg and the University of West Bohemia(UWB) in Pilsen as part of a cross-border cooperation. In technical applications, thermoplastic materials are oftenaffected by aging and a related deterioration of the mechanical properties. Therefore, it is necessary to identifythe aging behavior of thermoplastic materials. For this,experiments were performed for three thermoplasticmaterials, namely polypropylene (PP), ultra high mole -cular weight polyethylene (UHMWPE) and high impactstrength polystyrene (HIPS). For these experiments, a UV chamber was constructed according to the internationalstandard EN ISO 4892-3 for simulation of exposurebehind window glass. The results are evaluated by testing the flexural strength and the dynamic mechanicalresponse after a selected period of time under UV lightand then compared to untreated test specimens.}, language = {en} } @inproceedings{ValentinoRomanoEhrlichetal., author = {Valentino, Piergiorgio and Romano, Marco and Ehrlich, Ingo and Furgiuele, Franco and Gebbeken, Norbert}, title = {Mechanical characterization of basalt fibre reinforced plastic with different fabric reinforcements - Tensile tests and FE-calculations with representative volume elements (RVEs)}, series = {Acta Fracturae - XXll Convegno Nazionale IGF (Italiano Gruppo Frattura)}, booktitle = {Acta Fracturae - XXll Convegno Nazionale IGF (Italiano Gruppo Frattura)}, editor = {Iacovello, F. and Risitano, G. and Susmel, L.}, abstract = {This paper describes the results of tensile tests and finite element (FE) calculations with representative volume elements (RVEs) of basalt fibre reinforced plastic with two different types of fabric reinforcements. As fabric reinforcements show repeating ondulations of warp and fill yarn, simple mixtures laws reach their limits. That is the reason why the mesoscopic dimension, lying between the microscopic and the macroscopic dimension, has to be taken into account when a mechanical characterization of fabric reinforced composites is carried out. The aim of this work is to determine the stiffness of a fabric reinforced composite in warp and fill direction with numerical investigations. The simulations are based on FE-calculation with two different RVEs. The tensile tests and the FE-calculations have been carried out for two different types of basalt fabrics, namely twill 2/2 and twill 1/3. The comparison between the experimental data and the results of the FE-calculations are provided in order to support the validity of the proposed model.}, language = {en} } @inproceedings{Seppenhauser, author = {Seppenhauser, P.}, title = {Examinations of the Printer Head Prototype for UV Resins with Continous Fiber-Reinforcement}, series = {Applied Research Conference 2019 - ARC 2019, 8 July 2019, Regensburg}, booktitle = {Applied Research Conference 2019 - ARC 2019, 8 July 2019, Regensburg}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus}, publisher = {Pro Business GmbH}, address = {Berlin}, isbn = {978-3-96409-182-6}, pages = {241 -- 248}, subject = {3D-Druck}, language = {en} } @article{MicklitzRomanoEhrlichetal., author = {Micklitz, Matthias and Romano, Marco and Ehrlich, Ingo and Gebbeken, Norbert}, title = {The influence of ondulations in fabric reinforced layers on the damping properties of fibre-reinforced plastics}, series = {Applied Research Conference 2014 - ARC 2014, 5th July 2014, Ingolstadt}, journal = {Applied Research Conference 2014 - ARC 2014, 5th July 2014, Ingolstadt}, editor = {Ziemann, Olaf and Mottok, J{\"u}rgen and Pforr, Johannes}, publisher = {Shaker}, address = {Aachen}, pages = {306 -- 310}, language = {de} } @inproceedings{NiebauerSchmidEhrlich, author = {Niebauer, M. and Schmid, Vinzent and Ehrlich, Ingo}, title = {Failure Criteria of Adhesively Bonded Joints}, series = {Applied Research Conference 2015 - ARC 2015, N{\"u}rnberg, 3rd July 2015 - 16. Juli 2015}, booktitle = {Applied Research Conference 2015 - ARC 2015, N{\"u}rnberg, 3rd July 2015 - 16. Juli 2015}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Scharfenberg, J. and Ziemann, Olaf}, publisher = {Pro Business Verlag}, address = {Berlin}, isbn = {978-3863869458}, pages = {347 -- 351}, language = {en} } @techreport{HedererWagner, author = {Hederer, Sebastian and Wagner, Marcus}, title = {Entwicklung und Implementierung eines konstitutiven Modells zur Beschreibung der Plastizit{\"a}t von Dualphasenst{\"a}hle bei großen plastischen Deformationen}, series = {Forschungsbericht 2018 / Ostbayerische Technische Hochschule Regensburg}, journal = {Forschungsbericht 2018 / Ostbayerische Technische Hochschule Regensburg}, editor = {Baier, Wolfgang}, organization = {Ostbayerische Technische Hochschule Regensburg}, isbn = {9783981820911}, pages = {68 -- 69}, language = {de} } @techreport{ThumannSwidergalWagner, author = {Thumann, Philipp and Swidergal, Krzysztof and Wagner, Marcus}, title = {Experimentelle Ermittlung von Materialkennwerten und numerische Untersuchungen an einem gef{\"u}llten Elastomer}, series = {Forschungsbericht 2015 / Ostbayerische Technische Hochschule Regensburg}, journal = {Forschungsbericht 2015 / Ostbayerische Technische Hochschule Regensburg}, editor = {Baier, Wolfgang}, organization = {Ostbayerische Technische Hochschule Regensburg}, isbn = {978-3-00-048589-3}, pages = {49 -- 50}, language = {de} } @inproceedings{KochThumannWagner, author = {Koch, F. and Thumann, Philipp and Wagner, Marcus}, title = {Simulation with implicit time integration of high loaded areas of a forming tool for large presses using LS-DYNA}, series = {13. LS-DYNA Forum 2014, 6.-8. Oktober, Bamberg}, booktitle = {13. LS-DYNA Forum 2014, 6.-8. Oktober, Bamberg}, language = {en} } @inproceedings{MartinsWagnerWagnerHaufeetal., author = {Martins-Wagner, Magda and Wagner, Marcus and Haufe, Andr{\´e} and Liebold, Christian}, title = {A Graphical User Interface for Simulating Resin-Transfer-Molding Combining LS-DYNA and OpenFOAM}, series = {10th European LS-DYNA Conference 2015, W{\"u}rzburg, Germany}, booktitle = {10th European LS-DYNA Conference 2015, W{\"u}rzburg, Germany}, abstract = {The paper describes parts of the joint research project Swim-RTM including several industrial and academic partners. Its goal is to combine LS-DYNA and the open-source CFD solver OpenFOAM to simulate the production process of continuous fiber-reinforced plastics, particularly the resin-transfer-molding (RTM) process, in which the layers of dry fabric (unidirectional or woven) are formed in the mold (draping) and then filled with liquid resin with high pressure at injection points. Through a combined analysis of both the structural mechanical and the fluid dynamical phases, a better prediction and thereby optimization of the textile components properties as well as injection points can be achieved, improving the manufacturing process. The draping simulation of the fabric layers is carried out with LS-DYNA, while the injection simulation of the matrix material is performed in full 3D with OpenFOAM. A key question in this research project is how local porosities can be derived from the structural computation in the draping step. The purpose of the presented subproject is to develop a graphical user interface (GUI) to enable the simulation of the entire RTM process of long-fiber-reinforced components including the transfer of results between the draping and injection phases. The complete simulation task is relatively complex and involves several software packages, meaning a high effort for the user to get familiarized with. To circumvent this, the GUI aims at requiring from the user only the minimum necessary input data, creating and running the simulation and mapping tasks in the background, and showing graphically all demanded intermediate and final results. For the draping step several current fabric materials such as *MAT_034, *MAT_234, *MAT_235, *MAT_249 are available. Several modelling techniques for the composite setup are also conceivable, including a workflow similar to metal forming applications. In the injection step the fabric is modelled as a porous medium and different transport models and liquid resin types are at hand. For the data transfer between the draping and injection models, i.e. the mapping of data between shell and volume meshes within the developed GUI, first the OpenFOAM volume mesh is converted to LS-DYNA format and the necessary passing parameters are extracted from the output files, then the mapping tool DYNAmap [3] from DYNAmore GmbH is invoked, and finally the OpenFOAM command files are created. After the injection simulation is started and successfully terminated, information, such as the distribution of air inclusions or the shear stress distribution to analyze the reorientation of component fibers, is available and can be transferred from the 3D fluid mesh to an LS-DYNA shell mesh for further computations, for instance a crash simulation. This backward data mapping between volume and shell meshes can then be performed inside the GUI.}, language = {en} } @inproceedings{ThumannSwidergalWagner, author = {Thumann, Philipp and Swidergal, Krzysztof and Wagner, Marcus}, title = {Calculation and validation of material tests with specimens made out of filled elastomers}, series = {10th European LS-DYNA Conference 2015, W{\"u}rzburg}, booktitle = {10th European LS-DYNA Conference 2015, W{\"u}rzburg}, abstract = {In deep-drawing dies for steel sheet parts of car bodies huge masses are moved. To prevent vibrations, which occur by sudden acceleration or stopping of those masses, elastomeric tubular dampers [1] are used. The dampers are made out of carbon filled elastomers. A good knowledge about the material behaviour of metals is available. But for the numerical investigation of complete deep-drawing dies the elastomeric dampers must be taken into account, too. To characterize the material behaviour of the elastomers tensile tests and pressure tests were carried out. The received material data from the tests were read into LS-DYNA [2]. Simulation models of the tensile test and the pressure test were created for LS-DYNA according to the real dimensions and boundary conditions. For validation purposes, calculations of loading cycles were done to enable a comparison between test data and simulation results. For the calculations the implemented material model *MAT_SIMPLIFIED_RUBBER_WITH_DAMAGE (*MAT_183) was used. The comparison shows a good fitting between the test data and the calculation results with respect to the mechanical material behaviour by using this material model in single loading cases. The settings from the simulations of material tests were transferred to simulations of dampers, which are used in deep-drawing dies.}, language = {en} } @inproceedings{NonnErdelenPepplerKalwa, author = {Nonn, Aida and Erdelen-Peppler, Marion and Kalwa, Christoph}, title = {Numerical and experimental investigation of the influence of HAZ on the fracture behavior of longitudinal welded linepipes}, series = {18th European Conference on Fracture, Fracture of Materials and Structures from Micro to Macro Scale, Dresden, Germany}, booktitle = {18th European Conference on Fracture, Fracture of Materials and Structures from Micro to Macro Scale, Dresden, Germany}, abstract = {The present paper deals with the influence of heat affected zone (henceforth HAZ) on the fracture performance of longitudinal welded linepipes in dependence on constraint level. It has been shown that toughness values of HAZ obtained from standard fracture mechanics tests lead to uneconomic linepipe design for two reasons. The first reason is that laboratory specimens with higher constraint level generally exhibit lower fracture resistance compared to flawed linepipes. The second one has to do with a higher probability of cleavage failure occurrence in the laboratory specimen than in the linepipes due to larger areas of lower toughness (so called local brittle zones (LBZ)) intersected by crack front. In recent years numerous studies have been initiated with the objective to quantify the constraint level and thus to allow for less conservative linepipe safety assessment by applying constraint corrected toughness values. However, the main focus of these studies has hitherto been on the homogeneous materials, failing to account for the possible effects of different microstructures within the heterogeneous HAZ. This paper seeks to close this gap by reporting on results from tests on fracture mechanics specimens of a high strength X80 steel, i.e. SENB and SENT specimens as well as results from ring expansion tests. Both, deep and shallow cracks are inserted in the fracture mechanics specimens and rings targeting the fusion line (FL). By varying the initial crack size and sample type, different constraint levels are achieved and subsequently quantified using numerical methods. Besides constraint observations, post metallographic analyses are performed to identify exact HAZ microstructure involved at the crack tip. Finally, the influence of HAZ properties, flaw size and geometry on the failure behaviour of the linepipes has been demonstrated and assessed. Based on the combination of the results from constraint studies and the post metallographic analyses, the methodology is proposed which enables simple quantitative prediction of toughness values for safe and economic design of linepipes with flaws located in HAZ.}, language = {en} } @inproceedings{SchneiderNonnVoellingetal., author = {Schneider, Ingo and Nonn, Aida and V{\"o}lling, Alexander and Mondry, A. and Kalwa, Christoph}, title = {A damage mechanics based evaluation of dynamic fracture resistance in gas pipelines}, series = {Procedia Materials Science, Volume 3}, volume = {3}, booktitle = {Procedia Materials Science, Volume 3}, doi = {10.1016/j.mspro.2014.06.315}, pages = {1956 -- 1964}, abstract = {Investigation of running ductile fracture in gas transmission pipelines and the derivation of reliable crack arrest prediction methods belong to major topics in pipeline research. The yet available crack arrest criterion, known as the Battelle Two-Curve Method (BTCM), leads to reliable predictions up to grade X70 line pipe steels for which it has been validated. This includes specific limits in terms of mechanical properties, pressure and geometry. The application of this criterion to modern pipeline steels, i.e. especially grades X80 and beyond in combination with larger diameters and high pressure, has led to mispredictions of the BTCM. Hence, in order to ensure safe design of pipelines, new methods are required based on in depth knowledge and appropriate characterization of material resistance. This paper presents a procedure for the assessment of dynamic ductile fracture resistance based on combined experimental and numerical investigations. The procedure involves quasi-static and dynamic drop- weight tear testing (DWTT) on modified specimens with pre-fatigued crack for grades X65, X80 and X100 materials, and the application of cohesive zone (CZ) and Gurson-Tveergard-Needleman (GTN) models to describe ductile material damage. The damage model parameters are calibrated on basis of DWTT results and subsequently used to simulate dynamic crack propagation in a pipeline. The influence of material properties (strain hardening, toughness), pipe geometry, usage factor and decompression behaviour on ductile fracture propagation behaviour is studied and evaluated. The results will contribute to an enhanced understanding of major parameters controlling ductile fracture propagation and will help to establish a reliable procedure for safe design of new high-capacity pipelines with regard to crack arrest.}, language = {en} } @inproceedings{KofianiNonnWierzbickietal., author = {Kofiani, Kirki and Nonn, Aida and Wierzbicki, Tomasz and Kalwa, Christoph and Walters, Carey}, title = {Experiments and fracture modeling of high-strength pipelines for high and low stress triaxiality}, series = {22nd International Society of Offshore and Polar Engineering 2012 (ISOPE 2012), Rhodes, Greece, June 2012}, booktitle = {22nd International Society of Offshore and Polar Engineering 2012 (ISOPE 2012), Rhodes, Greece, June 2012}, abstract = {This paper provides results from a comprehensive study on mechanical characterization of high-strength pipeline steel, grade X100 using experimental and numerical methods. The material was characterized for anisotropic plasticity, fracture initiation for various states of stress, (pre-cracked) fracture toughness and uncracked ductility. The experimental program included tests on flat butterfly-shaped, central hole, notched and circular disk specimens for low stress triaxiality levels; as well as tests on round notched bar specimens and SENT fracture mechanics tests, for high values of stress triaxiality. This program covered a wide range of stress conditions and demonstrated its effect on the material resistance. Parallel to the experimental study, detailed numerical investigations were carried out to simulate all different experimental tests. Using an inverse method, a 3-parameter calibration was performed on the Modified Mohr-Coulomb (MMC) fracture model. Subsequently, the predictive capabilities of the MMC were evaluated by the comparison to the fracture toughness tests results, used extensively in the pipeline industry. The capabilities of the MIT fracture model have been demonstrated on an example of high strength offshore steel, X100. The outcome of this study was not only to provide, the overall characterization of the fracture behavior of this material as an example, but also to present the methodology on how to use the MMC model as a practical tool in pipeline design.}, language = {en} } @article{DinnebierEhrlich, author = {Dinnebier, Heinrich and Ehrlich, Ingo}, title = {The effects of severe temperature changes and high humidity on porous CFRP}, series = {Journal of Achievements in Materials and Manufacturing Engineering (JAMME)}, volume = {67}, journal = {Journal of Achievements in Materials and Manufacturing Engineering (JAMME)}, number = {1}, pages = {14 -- 20}, abstract = {Purpose: A route to manufacture porous carbon fiber reinforced plastic (CFRP) for study purposes is described. Design/methodology/approach: The porous CFRP is characterized using standard techniques such as matrix digestion as well as the more sophisticated method of high resolution Microfocus X-Ray Tomography (μCT). A comparison of the results of those methods is presented. The mass gains of specimens with a wide range of porosity have been measured both in constant humidity and in alternating environments. Findings: It could be shown that severe temperature changes can temporarily increase the moisture content of porous CFRP. However, after the return to a constant environment, the moisture content returns back to saturation levels. Furthermore, it could be shown by X-Ray Tomography that even under severe climatic conditions no permanent liquid water condensates inside the pores. Research limitations/implications: Using Microfocus Computed Tomography it could be shown that even after nearly a year under hot-wet conditions and more than 150 severe temperature cycles there is no liquid water detectable inside the pores. Originality/value: In this paper the effects of severe temperature changes and high humidity on porous CFRP.}, language = {en} } @techreport{EisenriedRomanoJungbaueretal., author = {Eisenried, Michael and Romano, Marco and Jungbauer, Bastian and Ehrlich, Ingo and Gebbeken, Norbert}, title = {Herstellung von unidirektional verst{\"a}rkten Prepregs im Labormaßstab - Einfluss von Fertigungsparametern auf die Materialqualit{\"a}t}, series = {Forschungsbericht 2013 / Ostbayerische Technische Hochschule Regensburg}, journal = {Forschungsbericht 2013 / Ostbayerische Technische Hochschule Regensburg}, address = {Regensburg}, pages = {51 -- 52}, language = {de} } @phdthesis{Ehrlich, author = {Ehrlich, Ingo}, title = {Impactverhalten schwach gekr{\"u}mmter Strukturen aus faserverst{\"a}rkten Kunststoffen}, address = {M{\"u}nchen}, language = {de} } @article{BodeEhrlich, author = {Bode, J. and Ehrlich, Ingo}, title = {Entwicklung eines finiten Elements f{\"u}r Sandwichanwendungen}, series = {Zeitschrift f{\"u}r Angewandte Mathematik und Mechanik (ZAMM), Journal of Applied Mathematics and Mechanics}, volume = {77}, journal = {Zeitschrift f{\"u}r Angewandte Mathematik und Mechanik (ZAMM), Journal of Applied Mathematics and Mechanics}, number = {1}, pages = {41 -- 42}, language = {de} } @article{RomanoHoinkesEhrlichetal., author = {Romano, Marco and Hoinkes, Carl J. J. and Ehrlich, Ingo and H{\"o}cherl, Johannes and Gebbeken, Norbert}, title = {Experimental investigation of energy dissipation properties of fibre reinforced plastics with hybrid layups under high-velocity impact loads}, series = {Journal of Achievements in Materials and Manufacturing Engineering (JAMME)}, volume = {64}, journal = {Journal of Achievements in Materials and Manufacturing Engineering (JAMME)}, number = {1}, pages = {14 -- 20}, abstract = {Purpose: The present work deals with the experimental investigation concerning the energy dissipation capacity of different kinds of reinforcement fibres in monolithic and hybrid layups under high velocity impact loads. The investigated kinds of fibres are carbon, glass and basalt. Design/methodology/approach: The test panels have been impregnated with thermoset resin. Curing was done by autoclave processing. In order to obtain comparable fibre volume contents of approx. 60 \% in the different layups (monolithic and hybrid without and with separating layer), curing cycles adapted to the type of layup have been identified. The resulting fibre volume content of the test panels has been determined both by weighing and experimentally by chemical extraction and calcination. The impact load was applied by an instrumented experimental setup. Thereby both commercially available bullets and bearing balls accelerated with weighted propellant in a sabot have been used as impactors. The measured values are the velocities of the bearing balls as the impactor before and after penetration of the test panels. Findings: In both cases the results show the energy dissipation capacity of each single kind of fibre in case of the monolithic layups as well as the enhanced properties of the hybrid stacked layups without and with the separating layer as a core material. Typical failure modes on the impact surface and on the outlet areas are identified. Research limitations/implications: The influence of the respective kind of impactors, namely bullets and bearing balls, on the evaluated results is identified. Thereby the bearing balls exhibited a higher degree of reproducibility due to several reasons. Originality/value: Fibre reinforced plastics with hybrid stacking sequences can be used as load-bearing structures and at the same time as safety structures for passengers in automotive or aerospace applications. Moreover, with the hybrid stacked composites lightweight concepts can efficiently be realized regarding energy saving issues.}, language = {en} } @article{SieglEhrlich, author = {Siegl, Marco and Ehrlich, Ingo}, title = {Transformation of the Mechanical Properties of Fiber-Reinforced Plastic Tubes from the Cartesian Coordinate System into the Cylindrical Coordinate System for the Application of Bending Models}, series = {Athens Journal of Technology \& Engineering}, volume = {4}, journal = {Athens Journal of Technology \& Engineering}, number = {1}, pages = {47 -- 62}, abstract = {Fiber-reinforced plastic (FRP) tubes are used in many different industries, such as electrical engineering and pipeline construction. The tubes are frequently subjected to bending loads, depending on the application. In order that the dimensioning of the tubes can be ensured, analytical bending models are used to calculate the resulting stresses, strains and displacements in the individual layers of the laminate. This enables the making of a statement about the failure of the fiber-reinforced tube by choosing an appropriate failure criterion. For the use of these bending models, it is necessary to understand the respective underlying theory. The theory provides the basis for the mathematical description of the mechanical properties for a single-layered tube and using the relationships between the stresses and strains that occur in the Cylindrical coordinate system for this calculation step. For this reason, a redefinition of the compliance matrix from the transformation about the winding angle to the Cylindrical coordinate system and a modification of the stress and strain vectors is necessary, because the defined Cartesian coordinate system of the model cannot be used for wounded FRP tubes. The transformation causes an exchange of entries in the compliance matrix, which remain in the correct relationship between the particular stress and strains. This step is not specified and may lead to incorrect results due to the incorrect entry of compliances. The present publication refers to sketch on this issue and represent a simplification of the changeover to the level required by the bending models notation of vectors in the form of a permutation. In addition, a new name for the pre-acquisition of the redefined compliances is given to prevent confusion when entering the material law of a bending model. Finally, the permuted and redefined compliances are proved in an example to determine their accuracy.}, language = {en} } @article{RomanoEhrlichGebbeken, author = {Romano, Marco and Ehrlich, Ingo and Gebbeken, Norbert}, title = {Parametric characterization of a mesomechanic kinematic in plain and twill weave 2/2 reinforced composites by FE-calculations}, series = {Archives of Materials Science and Engineering (ArchivesMSE)}, volume = {97}, journal = {Archives of Materials Science and Engineering (ArchivesMSE)}, number = {1-2}, publisher = {Index Copernicus}, issn = {1897-2764}, doi = {10.5604/01.3001.0013.2869}, pages = {20 -- 38}, abstract = {Purpose: A parametric characterization of a mesomechanic kinematic caused by ondulation in fabric reinforced composites is investigated by numerical investigations. Design/methodology/approach: Due to the definition of plain representative sequences of balanced plain-weave and twill-weave 2/2 fabric reinforced single layers based on sines the variable geometric parameters are the amplitude and the length of the ondulation. Findings: The mesomechanic kinematic can be observed in the FE analyses for both kinds of fabric constructions. Research limitations/implications: The FE analyses consider elasticity and contraction due to Poisson effects, respectively, of the model under selected longitudinal strains. Practical implications: The results are evaluated at relevant positions on the centre-line of the ondulated warp-yarn of the plain representative model. A direct and linear coupling in case of the transversal kinematic behaviour, and thereby a corresponding definite reduction of the evaluated longitudinal strains in terms of the difference of the applied and determined longitudinal strains is identified. Originality/value: Both characteristic purely kinematic reactions due to geometric constraints directly depend on the introduced degree of ondulation. This non-dimensional parameter relates amplitude and length of one complete ondulation, and thus represents the intensity of the ondulation of the respective fabric construction.}, language = {en} } @article{RomanoEhrlichGebbeken, author = {Romano, Marco and Ehrlich, Ingo and Gebbeken, Norbert}, title = {Structural mechanic material damping in fabric reinforced composites}, series = {Archives of Materials Science and Engineering (ArchivesMSE)}, volume = {88}, journal = {Archives of Materials Science and Engineering (ArchivesMSE)}, number = {1}, doi = {10.5604/01.3001.0010.7747}, pages = {12 -- 41}, abstract = {Purpose: A review regarding the acting mechanisms of structural dynamic material damping in fabric reinforced composites is presented. Design/methodology/approach: Mechanical acting principles identified by different investigations are considered. Aspects of the determination and calculation of structural mechanical material properties of fabric reinforced composites are described. Approaches intending the description and classification of ondulations in fabrics reinforced single layers are demonstrated. Findings: The mesomechanic geometry of fabrics is not considered sufficiently by relatively simple homogenization approaches. Yet, it significantly affects its structural dynamic material properties, especially the dynamic ones. Research limitations/implications: In each case the different damping mechanisms act coupled and occur at the same time. Therefore a separation procedure is required in any case. Practical implications: Against the background of the comparison and remarks of the presented papers a reasonable further procedure is recommended. Thereby, FE-calculations with a parametrical variation of the mesomechanic geometry in order to identify kinematic correlations due to geometric constraints are suggested. Originality/value: The idea of the representation of the geometric conditions in terms of a degree of ondulation is described. Such a non-dimensional specific value representing the intensity of the ondulation would enable the comparability of the results of different kinds of investigations.}, language = {en} } @article{ValentinoSgambitterraFurgiueleetal., author = {Valentino, Piergiorgio and Sgambitterra, Emanuele and Furgiuele, Franco and Romano, Marco and Ehrlich, Ingo and Gebbeken, Norbert}, title = {Mechanical characterization of basalt woven fabric composites}, series = {Frattura ed Integrit{\`a} Strutturale (Fracture and Structural Integrity)}, volume = {8}, journal = {Frattura ed Integrit{\`a} Strutturale (Fracture and Structural Integrity)}, number = {28}, doi = {10.3221/IGF-ESIS.28.01}, pages = {1 -- 11}, abstract = {Basalt fabric composite, with different twill wave reinforcements, i.e. twill 2/2 and twill 1/3, have been studied in this work by means of experimental tests and numerical finite element (FE) simulations. As fabric reinforcements show repeating undulations of warp and fill yarn, simple mixtures law cannot be applied. As a consequence, the mesoscopic scale, lying between the microscopic and the macroscopic one, has to be taken into account to mechanically characterize a fabric reinforced composite. The aim of this work is to evaluate the stiffness of a fabric reinforced composite in warp and fill direction. In particular a numerical FE model, assuming elliptical sections and sinusoidal shape of the yarns, has been implemented and experimental tests have been carried out in order to validate the proposed model. Finally, the strength and the failure modes le orientation, have been experimentally investigated.}, language = {en} } @techreport{SchlampEhrlich, author = {Schlamp, Matthias and Ehrlich, Ingo}, title = {Analyse des Impact-Verhaltens gekr{\"u}mmter Strukturbauteile von Luftfahrzeugen zur Entwicklung eines Struktur{\"u}berwachungssystems f{\"u}r faserverst{\"a}rkte Kunststoffe - BIRD}, series = {Forschung 2019 / Ostbayerische Technische Hochschule Regensburg}, journal = {Forschung 2019 / Ostbayerische Technische Hochschule Regensburg}, editor = {Baier, Wolfgang}, publisher = {VMK Verlag f{\"u}r Marketing \& Kommunikation GmbH \& Co. KG}, organization = {Ostbayerische Technische Hochschule Regensburg}, isbn = {978-3-9818209-6-6}, pages = {40 -- 41}, abstract = {Die in Flugvorausrichtung weisenden Bauteile von Luftfahrzeugen sind oftmals durch Einschl{\"a}ge aufgrund von Vogelschlag, Hagel oder aufgewirbelten Kleinteilen gef{\"a}hrdet. Diese Einschl{\"a}ge, sogenannte Impacts, weisen bei faserverst{\"a}rkten Kunststoffen ein stark kr{\"u}mmungs- und materialabh{\"a}ngiges Verhalten und Schadensausmaß auf. Impact-Sch{\"a}digungen f{\"u}hren oftmals zu hohen Reparaturkosten, welche durch eine genauere Kenntnis des Schadens verringert werden k{\"o}nnen. Zur Klassifizierung dieser Sch{\"a}digungen steht dabei vor allem das auftretende Frequenz signal des Impacts im Fokus der Untersuchungen.}, language = {de} } @article{RomanoHoinkesEhrlichetal., author = {Romano, Marco and Hoinkes, Carl J. J. and Ehrlich, Ingo and H{\"o}cherl, Johannes and Gebbeken, Norbert}, title = {Experimental investigation of fibre reinforced plastics with hybrid layups under high-velocity impact loads}, series = {Frattura ed Integrit{\`a} Strutturale (Fracture and Structural Integrity)}, volume = {8}, journal = {Frattura ed Integrit{\`a} Strutturale (Fracture and Structural Integrity)}, number = {29}, doi = {10.3221/IGF-ESIS.29.34}, pages = {384 -- 398}, abstract = {This paper deals with experimental investigations concerning energy dissipation capacity of different kinds of reinforcement fibres in monolithic and hybrid layups under high-velocity impact loads. The investigated kinds of fibres are carbon, glass and basalt fibres. Therefore test panels, using the same thermoset resin, were built up and cured by autoclave processing. The fibre volume content of the test panels has been determined. Furthermore the influence of a separating layer at selected positions in the hybrid stacked panels was investigated. The results show the influence and the energy dissipation capacity of each single kind of fibre and the enhanced properties for the hybrid layups by hybrid stacking sequences and the use of a separating core material.}, language = {en} } @techreport{PutzerRasmussenEhrlichetal., author = {Putzer, Michael and Rasmussen, John and Ehrlich, Ingo and Gebbeken, Norbert and Dendorfer, Sebastian}, title = {Muskuloskelettale Simulation zur Untersuchung des Einflusses geometrischer Parameter der Wirbelk{\"o}rper auf die Belastung der Lendenwirbels{\"a}ule}, series = {Forschungsbericht 2013 / Ostbayerische Technische Hochschule Regensburg}, journal = {Forschungsbericht 2013 / Ostbayerische Technische Hochschule Regensburg}, editor = {Baier, Wolfgang}, address = {Regensburg}, organization = {Ostbayerische Technische Hochschule Regensburg}, pages = {60 -- 61}, language = {de} } @article{RomanoMicklitzOlbrichetal., author = {Romano, Marco and Micklitz, Matthias and Olbrich, Florian and Bierl, Rudolf and Ehrlich, Ingo and Gebbeken, Norbert}, title = {Experimental investigation of damping properties of unidirectionally and fabric reinforced plastics by the free decay method}, series = {Journal of Achievements in Materials and Manufacturing Engineering}, volume = {63}, journal = {Journal of Achievements in Materials and Manufacturing Engineering}, number = {2}, pages = {65 -- 80}, abstract = {Purpose: of this paper is experimental investigation of damping properties of unidirectionally and fabric reinforced plastics by the free decay method. Design/methodology/approach: For the evaluation of the presumed effect experimental structural dynamic investigations comparing unidirectionally and fabric reinforced plastics are carried out. In detail the free decay behaviour of flat beamlike specimens under fixed-free boundary conditions and relatively constant and reproducible displacement excitation is investigated. Findings: The vibrating structure has been measured by a laser scanning vibrometer PSV 400 from POLYTEC. In both cases evaluation of the results yields enhanced damping properties of the specimens with fabric reinforcement compared to the unidirectionally reinforced specimens. The results justify the presumed acting of a mesomechanic kinematic. Research limitations/implications: The results show that in either case the material damping in terms of the logarithmic decrement of the fabric reinforced material is higher than the material damping in of the unidirectionally reinforced material. Additionally, when the fabric reinforced specimens are addressed, in each case the plain weave reinforced specimens exhibited higher values of the material damping as the twill weave 2/2 reinforced ones. Originality/value: Ondulations in fabrics as a textile semi-finished product are caused by the alternating crossing of warp and fill yarns. In the mesoscopic scale the acting of a mesomechanic kinematic is presumed to enhance the damping properties under cyclic elastic deformation. For the evaluation of the presumed effect experimental structural dynamic investigations comparing unidirectionally and fabric reinforced plastics are carried out.}, language = {en} } @article{LedentsovDuesterVolketal., author = {Ledentsov, Dmitry and D{\"u}ster, Alexander and Volk, Wolfram and Wagner, Marcus and Heinle, Ingo and Rank, Ernst}, title = {Model adaptivity for industrial application of sheet metal forming simulation}, series = {Finite Elements in Analysis and Design}, volume = {46}, journal = {Finite Elements in Analysis and Design}, number = {7}, doi = {10.1016/j.finel.2010.02.006}, pages = {585 -- 600}, abstract = {finite element simulation of sheet metal forming, shell elements are widely used. The limits of applicability of the shell elements are sometimes disregarded, which leads to an error in predictions of important values such as springback geometry. The underlying kinematic assumptions of the shell elements do not hold where the thickness of In the metal sheet approaches the value of the radius of curvature. Complex three-dimensional material behavior effects cannot be represented precisely as the result of the simplified kinematics. Here we present a model adaptivity scheme based on a model error indicator. The model-adaptive technique presented in this paper aides to resolve only the critical areas of the structure with a three-dimensional discretization while keeping reasonable computational cost by utilizing shell elements for the rest of the structure. The model error indicator serves as a guide for subsequent automatic adaptive re-meshing of the work-piece followed by a model-adaptive finite element analysis. The accuracy of the approximation obtained by the model-adaptive technique coincides well with that of a more expensive solution obtained with solid elements only.}, language = {en} } @inproceedings{WeghWagnerGaudlitzetal., author = {Wegh, Niels and Wagner, Marcus and Gaudlitz, Daniel and Finckh, Hermann and Klein, Markus}, title = {Numerical Simulation of Filling Process in Resin Transfer Molding}, series = {13th International Conference on Flow Processes in Composites Materials (FPCM-13), Kyoto, Japan}, booktitle = {13th International Conference on Flow Processes in Composites Materials (FPCM-13), Kyoto, Japan}, language = {en} } @inproceedings{MecklLubesederZausingeretal., author = {Meckl, D. and Lubeseder, Christian and Zausinger, C. and Wurmb, Ingo von and Meinhardt, Josef and Swidergal, Krzysztof and Wagner, Marcus}, title = {Simulation of press dies for large presses using the flexible multibody dynamics in Recurdyn}, series = {4th RecurDyn TechnologyDays 2014, M{\"u}nchen}, booktitle = {4th RecurDyn TechnologyDays 2014, M{\"u}nchen}, language = {en} } @inproceedings{GeithWagner, author = {Geith, Markus A. and Wagner, Marcus}, title = {Numerical Analysis Of Stent Delivery Systems During Pre- And Intraoperative Processes}, series = {Deutsches LS-DYNA Forum 2018, Bamberg}, booktitle = {Deutsches LS-DYNA Forum 2018, Bamberg}, language = {en} } @article{WiesentSpearNonn, author = {Wiesent, Lisa and Spear, Ashley and Nonn, Aida}, title = {Computational analysis of the effects of geometric irregularities on the interaction of an additively manufactured 316L stainless steel stent and a coronary artery}, series = {Journal of the Mechanical Behavior of Biomedical Materials}, volume = {125}, journal = {Journal of the Mechanical Behavior of Biomedical Materials}, publisher = {Elsevier}, issn = {1751-6161}, doi = {10.1016/j.jmbbm.2021.104878}, abstract = {Customized additively manufactured (laser powder bed fused (L-PBF)) stents could improve the treatment of complex lesions by enhancing stent-artery conformity. However, geometric irregularities inherent for L-PBF stents are expected to influence not only their mechanical behavior but also their interaction with the artery. In this study, the influence of geometrical irregularities on stent-artery interaction is evaluated within a numerical framework. Thus, computed arterial stresses induced by a reconstructed L-PBF stent model are compared to those induced by the intended stent model (also representing a stent geometry obtained from conventional manufacturing processes) and a modified CAD stent model that accounts for the increased strut thickness inherent for L-PBF stents. It was found that, similar to conventionally manufactured stents, arterial stresses are initially related to the basic stent design/topology, with the highest stresses occurring at the indentations of the stent struts. Compared to the stent CAD model, the L-PBF stent induces distinctly higher and more maximum volume stresses within the plaque and the arterial wall. In return, the modified CAD model overestimates the arterial stresses induced by the L-PBF stent due to its homogeneously increased strut thickness and thus its homogeneously increased geometric stiffness compared with the L-PBF stent. Therefore, the L-PBF-induced geometric irregularities must be explicitly considered when evaluating the L-PBF stent-induced stresses because the intended stent CAD model underestimates the arterial stresses, whereas the modified CAD model overestimates them. The arterial stresses induced by the L-PBF stent were still within the range of values reported for conventional stents in literature, suggesting that the use of L-PBF stents is conceivable in principle. However, because geometric irregularities, such as protruding features from the stent surface, could potentially damage the artery or lead to premature stent failure, further improvement of L-PBF stents is essential.}, language = {en} } @article{AndersBriemNovaketal., author = {Anders, M. and Briem, Ulrich and Novak, G. and Steinbach, G.}, title = {Inspektionsintervalle im Blick}, series = {Technische Logistik}, journal = {Technische Logistik}, publisher = {Huss-Medien}, address = {Berlin}, pages = {14 -- 17}, language = {de} } @article{ChatzitakisSafarovOpferkuchetal., author = {Chatzitakis, Paris and Safarov, Javid and Opferkuch, Frank and Dawoud, Belal and Hassel, Egon}, title = {Vapor pressures and activity coefficients of 2,2,2-trifluoroethanol in binary mixtures with 1,3-dimethyl-2-imidazolidinone and 2-pyrrolidone}, series = {Journal of Molecular Liquids}, volume = {305}, journal = {Journal of Molecular Liquids}, number = {May}, publisher = {Elsevier}, issn = {0167-7322}, doi = {10.1016/j.molliq.2020.112828}, abstract = {The vapor pressures of two binary mixtures containing 2-trifluoroethanol (TFE) + 1,3-dimethyl-2-imidazolidinone (DMI) and TFE + 2-pyrrolidone (PYR), were investigated at temperatures T = (274.15 to 423.15) K using two different static method installations. Both combinations were modelled using an extended Clausius-Clapeyron equation with concentration dependent parameters and the NRTL equation with temperature dependent parameters. The best fit was obtained using the NRTL equation.}, language = {en} } @article{Briem, author = {Briem, Ulrich}, title = {Die neue VDI 2500 : Faserseilwissen kompakt}, series = {Logistik f{\"u}r Unternehmen}, journal = {Logistik f{\"u}r Unternehmen}, number = {11-12}, pages = {36 -- 37}, abstract = {Die Richtlinie VDI 2500 „Faserseile" hat 1990 erstmals zusammenfassend den Stand der Technik auf dem Gebiet der Faserseile dargestellt und wertvolle Infor-mationen {\"u}ber Aufbau, Auswahl, Konfek-tionierung und {\"U}berwachung von Faser-seilen gegeben. Die jetzt erscheinende zweite Auflage enth{\"a}lt eine Vielzahl wichtiger technischer Neuerungen f{\"u}r die Praxis. Zu nennen sind hier die hochfesten Fasern und deren Beschichtung sowie die erstmals systematisch aufgef{\"u}hrten Sei-lendverbindungen und ein Ausblick auf die zuk{\"u}nftig bedeutsamen sogenannten Hybridseile. Eine Checkliste hilft bei der richtigen Auswahl und Bemessung von Faserseilen. Bei den Normen wurde - soweit m{\"o}glich - auf europ{\"a}ische Normen verwiesen.}, language = {de} } @article{Briem, author = {Briem, Ulrich}, title = {Umlaufbiegewechselzahl von verdichteten Seildr{\"a}hten}, series = {Draht}, journal = {Draht}, number = {6}, pages = {14 -- 15}, language = {de} } @article{Briem, author = {Briem, Ulrich}, title = {Biegesteifigkeit von Drahtseilen}, series = {Technische Logistik}, journal = {Technische Logistik}, number = {11-12}, publisher = {Huss-Medien}, address = {Berlin}, pages = {24 -- 25}, language = {de} } @article{GeilfussDawoud, author = {Geilfuß, Kristina and Dawoud, Belal}, title = {Analytical investigation of a zeolite-NaY-water adsorption heat and cold storage and its integration into a steam power process}, series = {Energy}, volume = {195}, journal = {Energy}, number = {March}, publisher = {Elsevier}, doi = {10.1016/j.energy.2020.116977}, abstract = {tabilizing the effects of greenhouse gas emissions on the atmosphere is a key step towards solving the global climate change problems. Storage technologies play an essential role in compensating the discrepancy between surplus energy and peak times. Sorption processes, in particular, offer an environment friendly way for almost loss-free heat (of adsorption or absorption) and cold storage. This work is dedicated first to analytically investigate the potential of applying NaY-Water/Zeolite as a working pair for heat and cold storage upon utilizing high temperature heat. It turned out that, the mass of the adsorber heat exchanger increases the useful specific heat stored from 229 kWh/tzeolite for the ideal storage to 538 kWh/tzeolite or even higher depending on the thermal capacity of the adsorber heat exchanger (AdsHX). Contrary to that trend, COP will decrease with increasing the thermal capacity of the AdsHX. Sensible heat losses between charging and discharging phases do have a negative effect on both stored heating capacity and COP. In addition, an innovative hybrid steam power cum adsorption storage process is introduced and analytically investigated at different ambient conditions and time scenarios for on-peak and off-peak durations over the day. The introduced hybrid process seems quite promising in achieving electrical power production and efficiency enhancements during peak load durations. The extent of enhancing both performance indicators increases with increasing the ambient temperature difference between peak and off-peak times.}, language = {en} } @article{SchorrCarrilloLiKaufholdetal., author = {Schorr, Philipp and Carrillo Li, Enrique Roberto and Kaufhold, Tobias and Rodriguez Hernandez, Jorge Antonio and Zentner, Lena and Zimmermann, Klaus and B{\"o}hm, Valter}, title = {Kinematic analysis of a rolling tensegrity structure with spatially curved members}, series = {Meccanica}, volume = {56}, journal = {Meccanica}, publisher = {Springer}, organization = {Springer}, issn = {0025-6455}, doi = {10.1007/s11012-020-01199-x}, pages = {953 -- 961}, abstract = {In this work, a tensegrity structure with spatially curved members is applied as rolling locomotion system. The actuation of the structure allows a variation of the originally cylindrical shape to a conical shape. Moreover, the structure is equipped with internal movable masses to control the position of the center of mass of the structure. To control the locomotion system a reliable actuation strategy is required. Therefore, the kinematics of the system considering the nonholonomic constraints are derived in this paper. Based on the resulting insight in the locomotion behavior a feasible actuation strategy is designed to control the trajectory of the system. To verify this approach kinematic analyses are evaluated numerically. The simulation data confirm the path following due to an appropriate shape change of the tensegrity structure. Thus, this system enables a two-dimensional rolling locomotion.}, language = {en} } @article{SteiningerGadererDawoudetal., author = {Steininger, Peter and Gaderer, Matthias and Dawoud, Belal and Gaderer, Matthias}, title = {Experimental and numerical study on the solar gain and heat loss of typical existing and refurbished German buildings}, series = {iCRBE Procedia}, volume = {1}, journal = {iCRBE Procedia}, number = {1}, publisher = {Weentech}, doi = {10.32438/icrbe.202035}, pages = {75 -- 93}, abstract = {This communication introduces an experimental setup for investigating the effect of solar radiation on the reduction of transmission heat losses and the steady state thermal conductance of uninsulated and insulated multi-layer wall samples. The setup consists of two adjacent climatic chambers, which share a common wall, in which the multi-layer wall samples are mounted. A solar simulator is applied within the outdoor air climatic chamber, whose radiation spectrum and radiation intensity are approximately equivalent to those of the sun. The first tests have been carried out on a wall sample with a typical structure of existing buildings from the year 1930 in Germany. In addition, a high-performance insulating plaster layer has been applied on a basic test sample (with existing building structure) to replicate and assess the refurbished scenario. Furthermore, a numerical investigation on the transient heat transfer process is carried out by using the simulation software COMSOL Multiphysics®. The experimental results of both uninsulated and insulated wall samples are validated against 1D and 3D models. As seen, the uninsulated wall, whose thermal conductance was experimentally determined to be equal to 1.79 W/(m²K), absorbs a heat flux of 208 W/m² through its external wall surface over a period of 8 hours. A fraction of 9.8 \% of the absorbed heat arrives as a gain on the internal wall and reduces the transmission heat losses by 11.7 \% over a period of 55 hours. On the other hand, the thermal conductivity of the insulation layer of the refurbished wall sample with micro hollow glass spheres was estimated by a parameter estimation procedure using the 3D model and the obtained experimental data. Using the estimated thermal conductivity, a thermal conductance of 0.42 W/(m²K) has been obtained for the refurbished wall sample.}, language = {en} } @inproceedings{BuenteRillRuggaberetal., author = {B{\"u}nte, Tilman and Rill, Georg and Ruggaber, Julian and Tobol{\´a}ř, Jakub}, title = {Modelling and Validation of the TMeasy Tyre Model for Extreme Parking Manoeuvres}, series = {Advances in Dynamics of Vehicles on Roads and Tracks II, Proceedings of the 27th Symposium of the International Association of Vehicle System Dynamics (IAVSD 2021): August 17-19, 2021, Saint Petersburg, Russia}, booktitle = {Advances in Dynamics of Vehicles on Roads and Tracks II, Proceedings of the 27th Symposium of the International Association of Vehicle System Dynamics (IAVSD 2021): August 17-19, 2021, Saint Petersburg, Russia}, editor = {Orlova, Anna and Cole, David}, publisher = {Springer}, address = {Cham}, isbn = {978-3-031-07305-2}, doi = {10.1007/978-3-031-07305-2_94}, pages = {1015 -- 1025}, abstract = {The TMeasy is a tyre model suitable for vehicle handling analyses and enables easy parametrisation. Recently, a convenient interface to Modelica was implemented by DLR to support the TMeasy also for vehicle modelling in multi-physical domains. This paper focuses especially on the particular problem of reliable reproduction of the tyre's bore torque which occurs during parking manoeuvres. It outlines the theory behind it, discusses the Modelica interface implementation, and presents the results of parameter identification which were achieved based on real experiments with DLR's research platform ROboMObil.}, language = {en} } @article{RillBauerTopcagic, author = {Rill, Georg and Bauer, Florian and Topcagic, Edin}, title = {Performance of leaf spring suspended axles in model approaches of different complexities}, series = {Vehicle System Dynamics}, volume = {60}, journal = {Vehicle System Dynamics}, number = {8}, publisher = {Taylor\&Francis}, doi = {10.1080/00423114.2021.1928249}, pages = {2871 -- 2889}, abstract = {Axles with leaf spring suspension systems are still a popular choice in many commercial vehicles. However, leaf springs are not in perfect conformity to standard multibody vehicle models because they combine guidance and suspension in one single element. Combining standard multibody vehicle models with sophisticated finite element leaf spring models results in rather complex and computing time-consuming solutions. Purely kinematic models, defined by lookup tables or the design kinematics approach, cover only some but not all features of the leaf spring suspension. As shown here, the five-link model, which incorporates a quasi-static solution of the leaf spring compliance, provides a very practical model. It is comparatively lean and provides results of sufficient accuracy in the whole application range.}, language = {en} } @inproceedings{SchorrSchaleOtterbachetal., author = {Schorr, Philipp and Schale, Florian and Otterbach, Jean Marc and Zentner, Lena and Zimmermann, Klaus and B{\"o}hm, Valter}, title = {Investigation of a Multistable Tensegrity Robot applied as Tilting Locomotion System}, series = {Proceedings of the 2020 IEEE International Conference on Robotics and Automation (ICRA): 31 May-31 August 2020, Paris}, booktitle = {Proceedings of the 2020 IEEE International Conference on Robotics and Automation (ICRA): 31 May-31 August 2020, Paris}, doi = {10.1109/ICRA40945.2020.9196706}, pages = {2932 -- 2938}, abstract = {This paper describes the development of a tilting locomotion system based on a compliant tensegrity structure with multiple stable equilibrium configurations. A tensegrity structure featuring 4 stable equilibrium states is considered. The mechanical model of the structure is presented and the according equations of motion are derived. The variation of the length of selected structural members allows to influence the prestress state and the corresponding shape of the tensegrity structure. Based on bifurcation analyses a reliable actuation strategy to control the current equilibrium state is designed. In this work, the tensegrity structure is assumed to be in contact with a horizontal plane due to gravity. The derived actuation strategy is utilized to generate tilting locomotion by successively changing the equilibrium state. Numerical simulations are evaluated considering the locomotion characteristics. In order to validate this theoretical approach a prototype is developed. Experiments regarding to the equilibrium configurations, the actuation strategy and the locomotion characteristics are evaluated using image processing tools and motion capturing. The results verify the theoretical data and confirm the working principle of the investigated tilting locomotion system. This approach represents a feasible actuation strategy to realize a reliable tilting locomotion utilizing the multistability of compliant tensegrity structures.}, language = {en} } @article{LotterBrebantEigenbergeretal., author = {Lotter, Luisa and Brebant, Vanessa and Eigenberger, Andreas and Hartmann, Robin and Mueller, Karolina and Baringer, Magnus and Prantl, Lukas and Schiltz, Daniel}, title = {"Topographic Shift": a new digital approach to evaluating topographic changes of the female breast}, series = {Archives of Gynecology and Obstetrics}, volume = {303}, journal = {Archives of Gynecology and Obstetrics}, number = {2}, publisher = {Springer Nature}, doi = {10.1007/s00404-020-05837-3}, pages = {515 -- 520}, abstract = {Purpose To assess precise topographic changes of the breast, objective documentation and evaluation of pre- and postoperative results are crucial. New technologies for mapping the body using digital, three-dimensional surface measurements have offered novel ways to numerically assess the female breast. Due to the lack of clear demarcation points of the breast contour, the selection of landmarks on the breast is highly dependent on the examiner, and, therefore, is prone to error when conducting before-after comparisons of the same breast. This study describes an alternative to volumetric measurements, focusing on topographic changes of the female breast, based on three-dimensional scans. Method The study was designed as an interventional prospective study of 10 female volunteers who had planned on having aesthetic breast augmentation with anatomical, textured implants. Three dimensional scans of the breasts were performed intraoperatively, first without and then with breast implants. The topographic change was determined as the mean distance between two three-dimensional layers before and after augmentation. This mean distance is defined as the Topographic Shift. Results The mean implant volume was 283 cc (SD = 68.6 cc, range = 210-395 cc). The mean Topographic Shift was 7.4 mm (SD = 1.9 mm, range = 4.8-10.7 mm). The mean Topographic Shifts per quadrant were: I: 8.0 mm (SD = 3.3 mm); II: 9.2 mm (SD = 3.1 mm); III: 6.9 mm (SD = 3.5 mm); IV: 1.9 mm (SD = 4.3 mm). Conclusion The Topographic Shift, describing the mean distance between two three-dimensional layers (for example before and after a volume changing therapy), is a new approach that can be used for assessing topographic changes of a body area. It was found that anatomical, textured breast implants cause a topographic change, particularly on the upper breast, in quadrant II, the decollete.}, language = {en} } @article{MikhaeilGadererDawoud, author = {Mikhaeil, Makram and Gaderer, Matthias and Dawoud, Belal}, title = {On the application of adsorber plate heat exchangers in thermally driven chillers}, series = {Applied Thermal Engineering}, volume = {220}, journal = {Applied Thermal Engineering}, publisher = {Elsevier}, doi = {10.1016/j.applthermaleng.2022.119713}, abstract = {The effect of both heat and mass transfer characteristic lengths (HTCL, MTCL) of two different adsorber plate heat exchangers (APHE), for application in an adsorption chiller, on the adsorption and desorption kinetics is investigated. Three representative test frames (TF1-TF3) are prepared to examine small-scale adsorbent samples of the microporous silica gel (Siogel of Oker-Chemie, Germany) applying the volumetric large-temperature-jump methodology at different operating conditions. Based on the obtained kinetic data, an analytical model has been developed to predict the specific cooling power (SCP) and the coefficient of performance (COP) of a single-bed adsorption chiller comprising the studied APHEs. It turned out that, within the tested range of HTCL and MTCL, it can be concluded that, the adsorption kinetics are mainly influenced by the MTCL, while the desorption kinetics are dominated by the HTCL of the adsorbent domain. Applying Siogel as loose pellets inside a newly introduced APHE results in of 423.3 and 182.7 W⋅kg-1, at the evaporator temperatures of 15 °C and 5 °C, respectively. Herein, the condenser and adsorber-end temperatures amount to 30 °C and the desorption-end temperature to 90 °C. The corresponding s amount to 0.50 and 0.40, respectively, which represent quite promising results for further design optimizations.}, language = {en} } @article{VerezBorriCrespoetal., author = {V{\´e}rez, David and Borri, Emiliano and Crespo, Alicia and Zsembinszki, Gabriel and Dawoud, Belal and Cabeza, Luisa F.}, title = {Experimental Study of a Small-Size Vacuum Insulated Water Tank for Building Applications}, series = {Sustainability}, volume = {13}, journal = {Sustainability}, number = {10}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/su13105329}, pages = {1 -- 11}, abstract = {Insulation of thermal energy storage tanks is fundamental to reduce heat losses and to achieve high energy storage efficiency. Although water tanks were extensively studied in the literature, the enhancement of the insulation quality is often overlooked. The use of vacuum insulation has the potential to significantly reduce heat losses without affecting the dimension of the storage system. This paper shows for the first time the results of the heat losses tests done for a 0.535 m3 water tank for residential building applications built with a double wall vacuum insulation. The different tests show that the rate of heat losses strictly depends on the temperature distribution inside the tank at the beginning of the experiment. Compared to a conventional water tank insulated with conventional materials, the U-value of the lateral surface was reduced by almost three times (from 1.05 W/K·m2 to 0.38 W/K·m2) using vacuum insulation. However, the bottom part, which is usually used to place the support parts and the piping, is the critical design part of those tanks acting as a thermal bridge with the ambient and enhancing heat losses.}, language = {en} } @inproceedings{SchorrBoehmZentneretal., author = {Schorr, Philipp and B{\"o}hm, Valter and Zentner, Lena and Zimmermann, Klaus}, title = {Design of a Vibration Driven Motion System Based on a Multistable Tensegrity Structure}, series = {ICINCO 2018: proceedings of the 15th International Conference on Informatics in Control, Automation and Robotics, Porto, Portugal, July 29-31, 2018}, volume = {613}, booktitle = {ICINCO 2018: proceedings of the 15th International Conference on Informatics in Control, Automation and Robotics, Porto, Portugal, July 29-31, 2018}, editor = {Gusikhin, Oleg and Madani, Kurosh}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-31992-2}, doi = {10.1007/978-3-030-31993-9_14}, pages = {302 -- 317}, abstract = {In this paper a novel approach to realize a uniaxial bidirectional vibration driven motion system with controllable direction of motion is investigated. The considered motion system bases on a tensegrity structure with multiple stable equilibrium configurations. The structure is in contact with a horizontal plane due to gravity and the actuation is realized by the harmonic change of the length of a selected member. Beside varying the actuation parameters, the direction of motion can be controlled by changing the equilibrium configuration of the tensegrity structure. In this paper the topology of the tensegrity structure and the parameter values are chosen appropriately to provide two symmetric equilibrium configurations. A change of the equilibrium state yields a novel configuration of the entire motion system which is symmetric to the original state. Utilizing the symmetry of the system the same actuation yields an opposite motion. This approach represents a reliable opportunity to control the direction of motion by changing the equilibrium state for constant actuation parameters. This paper focuses on the parameter selection and the design of the actuation of the vibration driven motion system. The working principle of the vibration driven motion system is verified by numerical simulations. This contribution represents the theoretical investigation for the further development of a prototype.}, language = {en} } @inproceedings{SchorrBoehmStepanetal., author = {Schorr, Philipp and B{\"o}hm, Valter and Stepan, G. and Zentner, Lena and Zimmermann, Klaus and St{\´e}p{\´a}n, G.}, title = {Multi-mode motion system based on a multistable tensegrity structure}, series = {Advances in Mechanism and Machine Science : Proceedings of the 15th IFToMM World Congress on Mechanism and Machine Science}, volume = {73}, booktitle = {Advances in Mechanism and Machine Science : Proceedings of the 15th IFToMM World Congress on Mechanism and Machine Science}, editor = {Uhl, Tadeusz}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-20130-2}, doi = {10.1007/978-3-030-20131-9_296}, pages = {3007 -- 3016}, abstract = {This paper presents a multi-mode motion system based on a compliant tensegrity structure with multiple stable equilibrium configurations. The motion system is in contact to an arbitrarily shaped rigid ground due to gravity. The movement is realized by changing successively between different equilibrium states. Depending on the strategy of changing the equilibrium configuration, different motion types occur. The reachable area of the motion system can be enlarged by adapting the motion type depending on the given environmental characteristics. Furthermore, the efficiency of the motion can be improved by choosing the most suitable motion mode. Theoretical studies regarding the change of the equilibrium states are introduced. Moreover, simulation results for the different motion modes tilting, vibration driven and jumping are illustrated. The resulting motion characteristics emphasize the advantageous adaptability of the motion system regarding to varying environmental conditions.}, language = {en} } @inproceedings{ChavezVegaJhohanScharffHelbigetal., author = {Chavez Vega Jhohan, and Scharff, Moritz and Helbig, Thomas and Alencastre, Jorge H. and B{\"o}hm, Valter and Behn, Carsten}, title = {Analysis of the Dynamic Behavior of Beams Supported by a Visco-Elastic Foundation in Context to Natural Vibrissa}, series = {Interdisciplinary Applications of Kinematics : Proceedings of the Third International Conference (IAK)}, volume = {71}, booktitle = {Interdisciplinary Applications of Kinematics : Proceedings of the Third International Conference (IAK)}, editor = {Kecskem{\´e}thy, Andr{\´e}s}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-030-16422-5}, doi = {10.1007/978-3-030-16423-2_5}, pages = {51 -- 59}, abstract = {Rodents use their mystacial vibrissae, e.g., to recognize the shape or determine the surface texture of an object. The vibrissal sensory system consists of two components: the hair shaft and the follicle-sinus complex (FSC). Both components affect the collection of information, but the impacts of the different properties are not completely clear. Borrowing the natural example, the goal is to design a powerful artificial sensor. The influence of a continuous visco-elastic support is analyzed for an artificial sensor following hypotheses about the FSC. Starting with a theoretical treatment of this scenario, the vibrissa is modeled as an Euler-Bernoulli bending beam with a partially continuous visco-elastic support. The numerical simulations are validated by experiments. Using a steel strip as a technical vibrissa and a magneto-sensitive elastomer (MSE) as representation of the artificial continuous visco-elastic support, FSC respectively, the first resonance frequency is determined.}, language = {en} } @inproceedings{Briem, author = {Briem, Ulrich}, title = {Automatically Inspection of Wire Ropes}, series = {2019 BTKS Proceedings : Xth INTERNATIONAL MAINTENANCE TECHNOLOGIES CONGRESS AND EXHIBITION : X. ULUSLARARASI BAKIM TEKNOLOJILERI, 26-27-28 SEPTEMBER 2019 DENIZLI / TURKEY}, booktitle = {2019 BTKS Proceedings : Xth INTERNATIONAL MAINTENANCE TECHNOLOGIES CONGRESS AND EXHIBITION : X. ULUSLARARASI BAKIM TEKNOLOJILERI, 26-27-28 SEPTEMBER 2019 DENIZLI / TURKEY}, isbn = {978-605-01-1288-7}, pages = {65 -- 74}, language = {en} } @inproceedings{Briem, author = {Briem, Ulrich}, title = {Neue Methode zur Bestimmung der Biegesteifigkeit von Drahtseilen}, series = {Der Kran - Leistungssteigerung, Leichtbau und Automatisierung : 27. Internationale Kranfachtagung 2019 : Begleitband zur Kranfachtagung am 07. M{\"a}rz 2019 in Bochum}, booktitle = {Der Kran - Leistungssteigerung, Leichtbau und Automatisierung : 27. Internationale Kranfachtagung 2019 : Begleitband zur Kranfachtagung am 07. M{\"a}rz 2019 in Bochum}, editor = {Scholten, Jan}, publisher = {Selbstverlag der Ruhr-Universit{\"a}t Bochum}, address = {Bochum}, isbn = {3-89194-226-5}, pages = {103 -- 112}, language = {de} } @incollection{Briem, author = {Briem, Ulrich}, title = {Rope line of free bent ropes}, series = {Exploring opportunities - synthetic/steel}, booktitle = {Exploring opportunities - synthetic/steel}, editor = {Dohm, Martin}, publisher = {OIPEEC}, address = {Meylan, France}, isbn = {978-1-7336004-0-8}, language = {en} } @inproceedings{CarrilloLiSchorrKaufholdetal., author = {Carrillo Li, Enrique Roberto and Schorr, Philipp and Kaufhold, Tobias and Rodr{\´i}guez Hern{\´a}ndez, Jorge Antonio and Zentner, Lena and Zimmermann, Klaus and B{\"o}hm, Valter}, title = {Kinematic analysis of the rolling locomotion of mobile robots based on tensegrity structures with spatially curved compressed components}, series = {Applicable Solutions in Non-Linear Dynamical Systems; 15th International Conference "Dynamical Systems - Theory and Applications" (DSTA 2019, 2-5 December, 2019, Lodz, Poland}, booktitle = {Applicable Solutions in Non-Linear Dynamical Systems; 15th International Conference "Dynamical Systems - Theory and Applications" (DSTA 2019, 2-5 December, 2019, Lodz, Poland}, editor = {Awrejcewicz, Jan and Ka{\'{z}}mierczak, Markek and Olejnik, Paweł}, publisher = {Wydawnictwo Politechniki Ł{\´o}dzkiej}, address = {Ł{\´o}d{\'{z}}, Polen}, isbn = {978-83-66287-30-3}, pages = {335 -- 344}, abstract = {In this work, a tensegrity structure with spatially curved members is applied as rolling locomotion system. The actuation of the structure allows a variation of the originally cylindrical shape to a conical shape. Moreover, the structure is equipped with internal movable masses to control the position of the center of mass of the structure. To control the locomotion system a reliable actuation strategy is required. Therefore, the kinematics of the system considering the nonholonomic constraints are derived in this paper. Based on the resulting insight in the locomotion behavior a feasible actuation strategy is designed to control the trajectory of the system. To verify this approach kinematic analyses are evaluated numerically. The simulation data confirm the path following due to an appropriate shape change of the tensegrity structure. Thus, this system enables a two-dimensional rolling locomotion. The use of mechanically compliant tensegrity structures in mobile robots is an attractive research topic, due to the possibility to adjust their mechanical properties reversibly during locomotion. In this paper rolling locomotion of mobile robots based on simple tensegrity structures, consisting of three compressed spatially curved members connected to a continuous net of prestressed tensional members, is discussed. Planar locomotion of these robots is induced by the movement of internal masses. The movement direction can be changed by changing the robot's shape between a cylinder and a truncated cone. The paper focuses on the description of the kinematics of these systems with respect to the shape change.}, language = {en} } @inproceedings{SchorrBoehmZentneretal., author = {Schorr, Philipp and B{\"o}hm, Valter and Zentner, Lena and Zimmermann, Klaus}, title = {Investigation of a tensegrity structure with multiple equilibrium configurations as jumping motion system}, series = {Theoretical Approaches in Non-Linear Dynamical Systems : Proceedings of the 15th Conference on Dynamical Systems -Theory and Applications}, booktitle = {Theoretical Approaches in Non-Linear Dynamical Systems : Proceedings of the 15th Conference on Dynamical Systems -Theory and Applications}, publisher = {Wydawnictwo Politechniki Ł{\´o}dzkiej}, address = {Ł{\´o}d{\'{z}}, Polen}, isbn = {978-83-66287-29-7}, pages = {465 -- 476}, abstract = {Often, the operating range of mobile robots is limited by environ- mental circumstances like obstacles or gaps. Therefore, an adaptation of the motion principle is required to enable an operating continuation of such robots. A jumping motion is a promising approach. This motion type allows to cross gaps or to overcome obstacles where common motion principles which bases on wheels or legs fail. However, especially during landing large forces occur as a consequence of the impact with the ground. This issue encourages the use of compliant tensegrity structures which feature a great shock resistance. In this paper a tensegrity structure with multiple equilibrium configurations is considered. The two-dimensional structure is equipped with two actuators to vary the prestress of the system. The tensegrity structure is in contact to a horizontal plane due to gravity. Two actuation strategies are derived. Beside varying the prestress state of the structure, a jump can be realized by changing the equilibrium configuration. Both actuation strategies and the corresponding motion characteristics are evaluated by numeric simulations. The results emphasize the advantageous properties of tensegrity structures for a jumping motion system. In particular, the multistabilty of the structure allows a simple actuation strategy for a reliable jumping motion.}, language = {en} } @phdthesis{Putzer, author = {Putzer, Michael}, title = {Development of subject-specific musculoskeletal models for studies of lumbar loading}, publisher = {Shaker Verlag}, address = {D{\"u}ren}, isbn = {978-3-8440-6695-1}, doi = {10.2370/9783844066951}, pages = {142}, abstract = {Anatomical differences between individuals are often neglected in musculoskeletal models, but they are necessary in case of subject-specific questions regarding the lumbar spine. A modification of models to each subject is complex and the effects on lumbar loading are difficult to assess. One objective of this work is to create a validated musculoskeletal human model, which facilitates a subject-specific modification of the lumbar geometry. In a second step, important parameters are identified in sensitivity studies and at last, a case study regarding multifidus muscle atrophy after a disc herniation is conducted. The results of the studies indicate that lumbar motion and loading is dependent on lumbar ligament stiffness. Furthermore, subject-specific modelling of the lumbar spine should include at least the vertebral height, disc height and lumbar lordosis. The results of the case study suggest that an overloading of the multifidus muscle could follow disc herniation. Additionally, a subsequent atrophy of the muscles could expose adjacent levels to an increased loading, but these findings are highly dependent on the individual.}, language = {en} } @techreport{SieglEhrlich, author = {Siegl, Marco and Ehrlich, Ingo}, title = {Internationale Forschung zum Biege- und Deformationsverhalten von faserverst{\"a}rkten Kunststoffrohren}, series = {Forschung 2019 / OTH Regensburg}, journal = {Forschung 2019 / OTH Regensburg}, editor = {Baier, Wolfgang}, publisher = {VMK Verlag f{\"u}r Marketing \& Kommunikation}, organization = {Ostbayerische Technische Hochschule Regensburg}, isbn = {978-3-9818209-6-6}, pages = {42 -- 43}, language = {de} }