@article{QiaoGradNonn, author = {Qiao, Yu and Grad, Marius and Nonn, Aida}, title = {Toward an Efficient and Robust Process-Structure Prediction Framework for Filigree L-PBF 316L Stainless Steel Structures}, series = {Metals}, volume = {15}, journal = {Metals}, number = {7}, publisher = {MDPI}, issn = {2075-4701}, doi = {10.3390/met15070812}, pages = {22}, abstract = {Additive manufacturing (AM), particularly laser powder bed fusion (L-PBF), provides unmatched design flexibility for creating intricate steel structures with minimal post-processing. However, adopting L-PBF for high-performance applications is difficult due to the challenge of predicting microstructure evolution. This is because the process is sensitive to many parameters and has a complex thermal history. Thin-walled geometries present an added challenge because their dimensions often approach the scale of individual grains. Thus, microstructure becomes a critical factor in the overall integrity of the component. This study focuses on applying cellular automata (CA) modeling to establish robust and efficient process-structure relationships in L-PBF of 316L stainless steel. The CA framework simulates solidification-driven grain evolution and texture development across various processing conditions. Model predictions are evaluated against experimental electron backscatter diffraction (EBSD) data, with additional quantitative comparisons based on texture and morphology metrics. The results demonstrate that CA simulations calibrated with relevant process parameters can effectively reproduce key microstructural features, including grain size distributions, aspect ratios, and texture components, observed in thin-walled L-PBF structures. This work highlights the strengths and limitations of CA-based modeling and supports its role in reliably designing and optimizing complex L-PBF components.}, language = {en} } @article{AfanasevHoeferHoltmannspoetteretal., author = {Afanasev, Anna and H{\"o}fer, Philipp and Holtmannsp{\"o}tter, Jens and Zimmer, Felix and Ehrlich, Ingo}, title = {Development of a continuous fiber-reinforced 3D printing process with a 6-axis robot arm: Process design and equipment}, series = {The International Journal of Advanced Manufacturing Technology}, journal = {The International Journal of Advanced Manufacturing Technology}, publisher = {Springer}, issn = {0268-3768}, doi = {10.1007/s00170-025-17263-3}, pages = {20}, abstract = {The utilisation of 3D printing processes in the fabrication of continuous fiber-reinforced composites confers a multitude of advantages, in particular flexible design based on structural requirements. In order to achieve greater flexibility, there is a necessity for 3D printing systems that allow for customisable material selection and fiber positioning. This paper presents the design of a robot-based 3D printing system that incorporates an in-situ impregnation line and flexibility regarding the machine code generation for fiber positioning. The development of the system enabled the attainment of an average fiber volume content of up to 37.12\%. In the tensile tests, material characteristics up to E1 = 24.7 GPa and strength of up to RM1 = 0.51 GPa were determined.}, language = {en} } @inproceedings{NonnMarx, author = {Nonn, Aida and Marx, P.}, title = {Validated Multiphysics Modeling For Advanced Pipeline Integrity Management}, series = {ADIPEC, November 4-7, 2024, Abu Dhabi, UAE}, booktitle = {ADIPEC, November 4-7, 2024, Abu Dhabi, UAE}, organization = {Society of Petroleum Engineers}, doi = {10.2118/222279-MS}, abstract = {The aim of this paper is to present practical steps for utilizing a validated multiphysics approach for fracture control in CO2 pipelines within the framework of Carbon Capture Transport and Storage (CCTS). Ensuring the arrest of running ductile fracture (RDF) is a crucial safety requirement for the transportation of dense-phase CO2. However, current standards rely on outdated and restrictive methods, imposing severe limitations on pipeline material and structural design. As a result, projects that fall outside these standards face the need for extremely costly tests, often leading to delays or cancellations of CCTS initiatives. This study introduces an advanced, validated, fully-coupled fluid-structure interaction (FSI) model designed to accurately predict fracture propagation in CO2 pipelines. A key advantage of this approach is its use of robust and reproducible calibration and validation procedures combined with high-quality material characterization data. The full coupling of structural, fluid, and backfill models is essential for obtaining precise results, not only in determining arrest occurrence but also in analyzing properties such as fracture velocity history, 3D pressure distributions behind the propagating crack, wall thinning, and crack tip opening angle. The FSI model has demonstrated its value as a cost-effective tool for safety assessments, enabling the development of fracture control plans that specify minimum required material properties and fluid compositions for optimized pipeline design, both onshore and offshore. Additionally, performing virtual studies with the parameterized FSI model enables the generation of synthetic data for training and validating a machine learning surrogate model. This surrogate model can be integrated into industrial practices, facilitating the application of multiphysics modeling without the need for extensive expertise.}, language = {en} } @article{PongratzTixWolfrumetal., author = {Pongratz, Christian and Tix, Janek and Wolfrum, Johannes and Gerke, Steffen and Ehrlich, Ingo and Br{\"u}nig, Michael}, title = {Test Setup for Investigating the Impact Behavior of Biaxially Prestressed Composite Laminates}, series = {Experimental Techniques}, journal = {Experimental Techniques}, publisher = {Springer Nature}, issn = {0732-8818}, doi = {10.1007/s40799-024-00701-4}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-70355}, pages = {14 S.}, abstract = {Instrumented impact testing and compression-after-impact testing are important to adequately qualify material behavior and safely design composite structures. However, the stresses to which fiber-reinforced plastic components are typically subjected in practice are not considered in the impact test methods recommended in guidelines or standards. In this paper, a test setup for investigating the impact behavior of composite specimens under plane uniaxial and biaxial preloading is presented. For this purpose, a special test setup consisting of a biaxial testing machine and a specially designed drop-weight tower was developed. The design decisions were derived from existing guidelines and standards with the aim of inducing barely visible impact damage in laminated carbon fiber-reinforced plastic specimens. Several measurement systems have been integrated into the setup to allow comprehensive observation of the impact event and specimen behavior. A feasibility test was performed with biaxially prestressed carbon fiber-reinforced plastic specimens in comparison with unstressed reference tests. The compressive-tensile prestressing resulted in lower maximum contact forces, higher maximum deflections, higher residual deflections and a different damage pattern, which was investigated by light microscopic analysis. Finally, the functionality of the experimental setup is discussed, and the results seem to indicate that the test setup and parameters were properly chosen to investigate the effect of prestresses on the impacts behavior of composite structures, in particular for barely visible subsequent damages.}, subject = {Faserverbundwerkstoff}, language = {en} } @misc{OlbrichPongratzBierletal., author = {Olbrich, Florian and Pongratz, Christian and Bierl, Rudolf and Ehrlich, Ingo}, title = {Method and System for Evaluating a Structural Integrity of an Aerial Vehicle}, language = {en} } @article{NonnKissPezeshkianetal., author = {Nonn, Aida and Kiss, B{\´a}lint and Pezeshkian, Weria and Tancogne-Dejean, Thomas and Cerrone, Albert R. and Kellermayer, Miklos and Bai, Yuanli and Li, Wei and Wierzbicki, Tomasz}, title = {Inferring mechanical properties of the SARS-CoV-2 virus particle with nano-indentation tests and numerical simulations}, series = {Journal of the mechanical behavior of biomedical materials}, volume = {148}, journal = {Journal of the mechanical behavior of biomedical materials}, publisher = {Elsevier}, issn = {1751-6161}, doi = {10.1016/j.jmbbm.2023.106153}, abstract = {The pandemic caused by the SARS-CoV-2 virus has claimed more than 6.5 million lives worldwide. This global challenge has led to accelerated development of highly effective vaccines tied to their ability to elicit a sustained immune response. While numerous studies have focused primarily on the spike (S) protein, less is known about the interior of the virus. Here we propose a methodology that combines several experimental and simulation techniques to elucidate the internal structure and mechanical properties of the SARS-CoV-2 virus. The mechanical response of the virus was analyzed by nanoindentation tests using a novel flat indenter and evaluated in comparison to a conventional sharp tip indentation. The elastic properties of the viral membrane were estimated by analytical solutions, molecular dynamics (MD) simulations on a membrane patch and by a 3D Finite Element (FE)-beam model of the virion's spike protein and membrane molecular structure. The FE-based inverse engineering approach provided a reasonable reproduction of the mechanical response of the virus from the sharp tip indentation and was successfully verified against the flat tip indentation results. The elastic modulus of the viral membrane was estimated in the range of 7-20 MPa. MD simulations showed that the presence of proteins significantly reduces the fracture strength of the membrane patch. However, FE simulations revealed an overall high fracture strength of the virus, with a mechanical behavior similar to the highly ductile behavior of engineering metallic materials. The failure mechanics of the membrane during sharp tip indentation includes progressive damage combined with localized collapse of the membrane due to severe bending. Furthermore, the results support the hypothesis of a close association of the long membrane proteins (M) with membrane-bound hexagonally packed ribonucleoproteins (RNPs). Beyond improved understanding of coronavirus structure, the present findings offer a knowledge base for the development of novel prevention and treatment methods that are independent of the immune system.}, language = {en} } @article{WiesentStockerNonn, author = {Wiesent, Lisa and Stocker, Felix and Nonn, Aida}, title = {Investigating the influence of geometric parameters on the deformation of laser powder bed fused stents using low-fidelity thermo-mechanical analysis}, series = {Materialia}, volume = {28}, journal = {Materialia}, publisher = {Elsevier}, doi = {10.1016/j.mtla.2023.101774}, abstract = {Maintaining dimensional accuracy is a major challenge of laser powder bed fusion (L-PBF) preventing its application for more complex and filigree L-PBF structures in industrial practice. Previous studies have shown that residual stresses and distortion of benchmark L-PBF components may be predicted by sequential thermo-mechanical analyses. However, the reliability of these analyses for more complex structures must be critically questioned, as comprehensive validation and sensitivity analyses are scarce. In this paper, we present a calibrated and validated low-fidelity sequential thermo-mechanical finite element analysis (FEA) of a tubular L-PBF lattice structure, i.e., an aortic stent, where pronounced local deformation is expected. As a first step, the finite element model was extensively calibrated using experimental data to ensure reproducibility of the simulation results. Thereupon, geometric features critical to the distortion of L-PBF lattice structures and measures to compensate for the distortion, such as inversion of the distorted L-PBF structure, were investigated. It was found that the distortion of the L-PBF lattice structures can be reduced, but not completely prevented, by increasing the strut angles, increasing the strut thickness, and decreasing the transition radius in the area of merging struts. FEA-based inversion of the numerically predicted deformed structure minimized distortion, resulting in the L-PBF aortic stent approximating the intended CAD geometry even with a small strut thickness. This work shows that low-fidelity sequential thermo-mechanical FEA can be used not only for the analysis and deformation compensation of reference structures, but also for the analysis of more complex filigree structures with pronounced local deformation.}, language = {en} } @misc{JudenmannPongratzEhrlichetal., author = {Judenmann, Anna and Pongratz, Christian and Ehrlich, Ingo and H{\"o}fer, Philipp and Holtmannsp{\"o}tter, Jens}, title = {Additive Fertigung von endlosfaserverst{\"a}rkten Kunststoffstrukturen}, series = {M{\"u}nchner Leichtbauseminar 2022, 26. October 2022, 16. November 2022, 30 November 2022, Munich/Neubiberg/Garching}, journal = {M{\"u}nchner Leichtbauseminar 2022, 26. October 2022, 16. November 2022, 30 November 2022, Munich/Neubiberg/Garching}, abstract = {Additive Fertigung hat sich in zahlreichen industriellen Anwendungen etabliert und bildet eine wichtige Schl{\"u}sseltechnologie. Im Gegensatz zu metallischen Werkstoffen, haben additiv gefertigte Bauteile aus Kunststoffen geringere Festigkeit und Steifigkeit, sodass sich ihre Verwendung als lasttragende Strukturen schwierig gestaltet. Insbesondere der Einsatz von endlosen Verst{\"a}rkungsfasern kann die mechanischen Eigenschaften additiv gefertigter Strukturen signifikant verbessern und die Fertigung hochbelastbarer Faserverbundstrukturen im 3D-Druckverfahren erm{\"o}glichen. Daher gilt es aktuell notwendige Anlagen und Prozessketten f{\"u}r den Fertigungsprozess aber auch Vorgehensweisen f{\"u}r die belastungsoptimierte Auslegung der Faserverl{\"a}ufe innerhalb des Bauteils zu entwickeln, um so das Themengebiet „Endlosfaserverst{\"a}rkter 3D-Druck" weiter voranzutreiben. F{\"u}r mehr r{\"a}umliche Freiheit bei der Positionierung der Druckbahnen k{\"o}nnen industrieroboterbasierte Systeme eingesetzt werden, um so das Potenzial gerichteter Bauweise von Faserverbundstrukturen auch im additiven Fertigungsprozess vollumf{\"a}nglich aussch{\"o}pfen zu k{\"o}nnen. Dabei erm{\"o}glicht ihr Einsatz auch eine r{\"a}umliche Ablage der Faserverst{\"a}rkung, wobei f{\"u}r die Materialablage ein geeigneter 3D-Druckkopf erforderlich ist. F{\"u}r die Implementierung der Faserverst{\"a}rkung ist zudem eine dem Lastfall entsprechende Auslegung des Bauteils sowie die Ermittlung einer sinnvollen Faserpositionierung innerhalb des Bauteils erforderlich, wobei unterschiedliche Variablen aus den Bereichen Material, Struktur und Fertigungsprozess ber{\"u}cksichtigt werden m{\"u}ssen. Im Rahmen des Vortrages werden die Herausforderungen der Technologieentwicklung des endlosfaserverst{\"a}rkten 3D-Drucks aufgegriffen sowie auf eine belastungsorientierte Faserpositionierung n{\"a}her eingegangen. Aktuelle Erkenntnisse werden diskutiert sowie eine Entwurfsmethodik f{\"u}r die Prozesspfadgenerierung vorgeschlagen.}, language = {de} } @article{SadeghpourNonn, author = {Sadeghpour, Ebrahim and Nonn, Aida}, title = {Data-driven models for structure-property prediction in additively manufactured steels}, series = {Computational Materials Science}, volume = {215}, journal = {Computational Materials Science}, publisher = {Elsevier}, doi = {10.1016/j.commatsci.2022.111782}, abstract = {Data-driven models are developed to predict the mechanical properties of polycrystalline materials. The case study is the prediction of the yield strength of a 3D-printed 316L steel from morphological and crystallographic features. Three different artificial intelligence models including feed-forward (FNN), convolution (CNN), and graph (GNN) neural networks are employed to train the data-driven models and are compared in terms of performance and computational requirements. The dataset required for training is generated by performing crystal plasticity finite element simulations. The FNN model has the smallest input size and takes in some statistical parameters describing the material microstructure, but its accuracy is relatively low. The CNN approach inputs voxel-based realizations of the microstructure and is able to give accurate estimations; however, its training process is time-consuming and computationally expensive. In the GNN approach, the polycrystalline material is represented by a graph whose nodes and lines represent the grains and adjacency between grains. It is observed that GNN yields a better performance compared to the other two approaches and has the capability of handling complex tasks.}, language = {en} } @inproceedings{XueParedesNonnetal., author = {Xue, Lufeng and Paredes, Marcelo and Nonn, Aida and Wierzbicki, Tomasz}, title = {Modeling of Crack Propagation in Defective X100 Line Pipes}, series = {ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering: August 3-7, 2020, virtual, online}, booktitle = {ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering: August 3-7, 2020, virtual, online}, publisher = {American Society of Mechanical Engineers}, address = {New York}, isbn = {978-0-7918-8434-8}, doi = {10.1115/OMAE2020-18048}, pages = {8}, abstract = {A comprehensive experimental program is carried out to determine material parameters for fracture initiation and propagation in X100 pipeline steels. The quadratic Hill'48 yield function along with an isotropic hardening are used to describe plastic flow at large deformation and a phenomenological fracture criterion to predict fracture initiation. Fracture mechanics SENT specimens are used to calibrate post-initiation softening parameters necessary for ductile crack propagation in thick components. Once the material model parameters set is complete a final comparison is conducted with ring expansion test on same material.}, language = {en} } @misc{SchimmerGebhardtMotschEichmannetal., author = {Schimmer, Florian and Gebhardt, Jakob and Motsch-Eichmann, N. and Hausmann, Joachim M. and Ehrlich, Ingo}, title = {The effect of curvature on the low-velocity impact resistance of CF/PEEK laminates}, series = {30 Years IVW Anniversary Colloquium, Leibnitz-Institut f{\"u}r Verbundwerkstoffe Kaiserslautern, 2021}, journal = {30 Years IVW Anniversary Colloquium, Leibnitz-Institut f{\"u}r Verbundwerkstoffe Kaiserslautern, 2021}, language = {en} } @article{XueKeimParedesetal., author = {Xue, Lufeng and Keim, Vincent and Paredes, Marcelo and Nonn, Aida and Wierzbicki, Tomasz}, title = {Anisotropic effects on crack propagation in pressurized line pipes under running ductile fracture scenarios}, series = {Engineering fracture mechanics}, volume = {249}, journal = {Engineering fracture mechanics}, publisher = {Elsevier}, doi = {10.1016/j.engfracmech.2021.107748}, abstract = {The current analyses present results of running ductile fracture propagation in high strength X100 line pipe steels under the influence of anisotropy. Mechanical anisotropy is commonly available in pipe products as a result of the manufacturing process, especially, those subjected to hot/cold-worked deformation. The outcomes of the present analyses show that its effect on the behavior of running ductile fracture in cracked pipes undergoing depressurization is meaningful. For instance, the Crack-Tip Opening Angle (CTOA) not only exhibits a strong dependence to the pipe's diameter size, but also to the material's anisotropy nature when compared to a hypothetical isotropic material. Moreover, laboratory scale tests such as those performed on Battelle Drop Weight Tear (BDWT) samples provide useful information about initiation of ductile crack propagation when the anisotropy features are taken into account in the material description.}, language = {en} } @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{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{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} } @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 = {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{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} } @article{WiesentSchultheissLullaetal., author = {Wiesent, Lisa and Schultheiß, Ulrich and Lulla, Philipp and Noster, Ulf and Schratzenstaller, Thomas and Schmid, Christof and Nonn, Aida and Spear, Ashley}, title = {Computational analysis of the effects of geometric irregularities and post-processing steps on the mechanical behavior of additively manufactured 316L stainless steel stents}, series = {PLoS ONE}, volume = {15}, journal = {PLoS ONE}, number = {12}, publisher = {PLOS}, doi = {10.1371/journal.pone.0244463}, pages = {1 -- 30}, abstract = {Advances in additive manufacturing enable the production of tailored lattice structures and thus, in principle, coronary stents. This study investigates the effects of process-related irregularities, heat and surface treatment on the morphology, mechanical response, and expansion behavior of 316L stainless steel stents produced by laser powder bed fusion and provides a methodological approach for their numerical evaluation. A combined experimental and computational framework is used, based on both actual and computationally reconstructed laser powder bed fused stents. Process-related morphological deviations between the as-designed and actual laser powder bed fused stents were observed, resulting in a diameter increase by a factor of 2-2.6 for the stents without surface treatment and 1.3-2 for the electropolished stent compared to the as-designed stent. Thus, due to the increased geometrically induced stiffness, the laser powder bed fused stents in the as-built (7.11 ± 0.63 N) or the heat treated condition (5.87 ± 0.49 N) showed increased radial forces when compressed between two plates. After electropolishing, the heat treated stents exhibited radial forces (2.38 ± 0.23 N) comparable to conventional metallic stents. The laser powder bed fused stents were further affected by the size effect, resulting in a reduced yield strength by 41\% in the as-built and by 59\% in the heat treated condition compared to the bulk material obtained from tensile tests. The presented numerical approach was successful in predicting the macroscopic mechanical response of the stents under compression. During deformation, increased stiffness and local stress concentration were observed within the laser powder bed fused stents. Subsequent numerical expansion analysis of the derived stent models within a previously verified numerical model of stent expansion showed that electropolished and heat treated laser powder bed fused stents can exhibit comparable expansion behavior to conventional stents. The findings from this work motivate future experimental/numerical studies to quantify threshold values of critical geometric irregularities, which could be used to establish design guidelines for laser powder bed fused stents/lattice structures.}, subject = {Koronarendoprothese}, 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{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} } @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} } @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{KramerJonesMostafaetal., author = {Kramer, Sharlotte L. B. and Jones, Amanda and Mostafa, Ahmed and Ravaji, Babak and Tancogne-Dejean, Thomas and Roth, Christian C. and Nonn, Aida}, title = {The third Sandia fracture challenge: predictions of ductile fracture in additively manufactured metal}, series = {International Journal of Fracture}, volume = {218}, journal = {International Journal of Fracture}, publisher = {Springer Nature}, doi = {10.1007/s10704-019-00361-1}, pages = {5 -- 61}, abstract = {The Sandia Fracture Challenges provide a forum for the mechanics community to assess its ability to predict ductile fracture through a blind, round-robin format where mechanicians are challenged to predict the deformation and failure of an arbitrary geometry given experimental calibration data. The Third Challenge (SFC3) required participants to predict fracture in an additively manufactured (AM) 316L stainless steel bar containing through holes and internal cavities that could not have been conventionally machined. The volunteer participants were provided extensive data including tension and notched tensions tests of 316L specimens built on the same build-plate as the Challenge geometry, micro-CT scans of the Challenge specimens and geometric measurements of the feature based on the scans, electron backscatter diffraction (EBSD) information on grain texture, and post-test fractography of the calibration specimens. Surprisingly, the global behavior of the SFC3 geometry specimens had modest variability despite being made of AM metal, with all of the SFC3 geometry specimens failing under the same failure mode. This is attributed to the large stress concentrations from the holes overwhelming the stochastic local influence of the AM voids and surface roughness. The teams were asked to predict a number of quantities of interest in the response based on global and local measures that were compared to experimental data, based partly on Digital Image Correlation (DIC) measurements of surface displacements and strains, including predictions of variability in the resulting fracture response, as the basis for assessment of the predictive capabilities of the modeling and simulation strategies. Twenty-one teams submitted predictions obtained from a variety of methods: the finite element method (FEM) or the mesh-free, peridynamic method; solvers with explicit time integration, implicit time integration, or quasi-statics; fracture methods including element deletion, peridynamics with bond damage, XFEM, damage (stiffness degradation), and adaptive remeshing. These predictions utilized many different material models: plasticity models including J2 plasticity or Hill yield with isotropic hardening, mixed Swift-Voce hardening, kinematic hardening, or custom hardening curves; fracture criteria including GTN model, Hosford-Coulomb, triaxiality-dependent strain, critical fracture energy, damage-based model, critical void volume fraction, and Johnson-Cook model; and damage evolution models including damage accumulation and evolution, crack band model, fracture energy, displacement value threshold, incremental stress triaxiality, Cocks-Ashby void growth, and void nucleation, growth, and coalescence. Teams used various combinations of calibration data from tensile specimens, the notched tensile specimens, and literature data. A detailed comparison of results based of these different methods is presented in this paper to suggest a set of best practices for modeling ductile fracture in situations like the SFC3 AM-material problem. All blind predictions identified the nominal crack path and initiation location correctly. The SFC3 participants generally fared better in their global predictions of deformation and failure than the participants in the previous Challenges, suggesting the relative maturity of the models used and adoption of best practices from previous Challenges. This paper provides detailed analyses of the results, including discussion of the utility of the provided data, challenges of the experimental-numerical comparison, defects in the AM material, and human factors.}, 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} } @phdthesis{Putzer, author = {Putzer, Michael}, title = {Development of subject-specific musculoskeletal models for studies of lumbar loading}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:706-5924}, pages = {140}, 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. The objective of this thesis is to create a validated musculoskeletal model of the human body, which facilitates a subject-specific modification of the geometry of the lumbar spine. Furthermore, important parameters are identified in sensitivity studies and a case study regarding multifidus muscle atrophy after a disc herniation is conducted. Therefore, a generic model is heavily modified and a semi-automatic process is implemented. This procedure remodels the geometry of the lumbar spine to a subject-specific one on basis of segmented medical images. The resulting five models are validated with regard to the lumbar loading at the L4/L5 level. The influence of lumbar ligament stiffness is determined by changing the stiffness values of all lumbar ligaments in eleven steps during a flexion motion. Sensitivities of lumbar loading to an altered geometry of the lumbar spine are identified by varying ten lumbar parameters in simulations with each model in four postures. The case study includes an analysis of the loading of the multifidus muscle and of the lumbar discs throughout various stages of disc herniation. This time each model performs four motions with two different motion rhythms. The results 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.}, subject = {Lendenwirbels{\"a}ule}, 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} } @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} } @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{RomanoEisenriedJungbaueretal., author = {Romano, Marco and Eisenried, Michael and Jungbauer, Bastian and Ehrlich, Ingo and Gebbeken, Norbert}, title = {Influence of parameters of the production process on the material quality of unidirectionally reinforced prepregs}, series = {Journal of Achievements in Materials and Manufacturing Engineering (JAMME)}, volume = {68}, journal = {Journal of Achievements in Materials and Manufacturing Engineering (JAMME)}, number = {1}, pages = {32 -- 44}, abstract = {Purpose: A prepreg production device in laboratory scale is used to develop the production process of unidirectionally reinforced prepregs. Design/methodology/approach: The aim of the prepreg production device is to impregnate different types of reinforcement fibers with an arbitrarily selectable thermoset matrix system that completely satisfies the requirements for autoclave processing. As the prepreg production device is designed and built up modularly every module corresponds one step in the process. Findings: To identify the parameters of the production process and investigate its sensitivity on the material quality of both the prepreg as an uncured semi-finished product and the composite as the cured material experimental investigations regarding the resin flow, fiber volume content, mass per unit area and void content are carried out. Overall four material combinations have been investigated, where in each case the selected impregnation temperature and the width of the impregnation gap has been reproducibly varied in selected steps. Research limitations/implications: The experimental characterization of the prepregs and of the composite material is carried out according to German standards.}, language = {en} } @inproceedings{PongratzEhrlich, author = {Pongratz, Christian and Ehrlich, Ingo}, title = {Structural Dynamic Analysis of Thin Composite Plates Using Noncontact Measurement and Excitation}, 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}, isbn = {978-3-86460-494-2}, pages = {351 -- 358}, language = {en} } @inproceedings{LindnerBerndtJungbaueretal., author = {Lindner, Matthias and Berndt, Dominik and Jungbauer, Bastian and Ehrlich, Ingo and Schreiner, Rupert and Pipa, Andrei V. and Hink, R{\"u}diger and Foest, R{\"u}diger and Brandenburg, Ronny and Max, Alexander and Caspari, Ralf}, title = {Fabrication, surface integration and testing of miniaturized dielectric barrier discharge plasma actuators for active flow control applications}, series = {AIAA Aviation 2019 Forum, 17-21 June 2019, Dallas, Texas}, booktitle = {AIAA Aviation 2019 Forum, 17-21 June 2019, Dallas, Texas}, doi = {10.2514/6.2019-2998}, language = {en} } @inproceedings{LindnerBerndtTschurtschenthaletal., author = {Lindner, Matthias and Berndt, Dominik and Tschurtschenthal, Karl and Ehrlich, Ingo and Jungbauer, Bastian and Schreiner, Rupert and Pipa, Andrei V. and Hink, R{\"u}diger and Foest, R{\"u}diger and Brandenburg, Ronny and Neuwirth, Daniel and Karpen, Norbert and Bonaccurso, Elmar and Weichwald, Robert and Max, Alexander and Caspari, Ralf}, title = {Aircraft Icing Mitigation by DBD-based Micro Plasma Actuators}, series = {AIAA AVIATION 2020 FORUM: June 15-19, 2020}, booktitle = {AIAA AVIATION 2020 FORUM: June 15-19, 2020}, doi = {10.2514/6.2020-3243}, abstract = {We present the application of plasma actuators as a technology for ice prevention at airfoils. The miniaturized dielectric barrier discharge (DBD) plasma actuators (PA) were fabricated by means of microelectromechanical systems (MEMS). We elucidate how to make the actuator samples scalable and applicable to any desired shape by the use of flexible inorganic zirconia substrates. For this purpose, we applied our developed embedding method to integrate the micro actuators in modern carbon/glass fiber reinforced polymer (CFRP/GFRP) materials. Next, the embedded actuator samples were mounted on a mechanical air profile-like fixture and placed in the icing wind tunnel iCORE. The samples were tested in rime ice conditions at temperatures of -15 to -20° C and air speeds up to 30 m/s. Unlike other groups we used a thin film zirconia substrate as dielectric for the plasma actuator. Due to the low substrate thickness of just 150 µm, an operating voltage of 2 kVRMS is already sufficient enough for a stable plasma formation. The experiments show that the operated actuator was able to prevent the ice formation and first indications of a De-icing function were also found. Hence, we show that it is feasible to realize an anti-icing system with zirconia-based plasma actuators operated at lower voltages compared to conventional ones.}, language = {en} } @inproceedings{EisenriedRomanoJungbaueretal., author = {Eisenried, Michael and Romano, Marco and Jungbauer, Bastian and Ehrlich, Ingo and Gebbeken, Norbert}, title = {Influence of parameters of the production process on the material quality of unidirectionally reinforced prepregs}, series = {Applied Research Conference 2013, ARC 2013 ; 17th and 18th October 2013, Deggendorf}, booktitle = {Applied Research Conference 2013, ARC 2013 ; 17th and 18th October 2013, Deggendorf}, editor = {Ziemann, Olaf and Bogner, Werner and Mottok, J{\"u}rgen}, publisher = {Shaker}, address = {Aachen}, pages = {70 -- 75}, 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} } @inproceedings{HoinkesRomanoEhrlichetal., author = {Hoinkes, Carl J. J. and Romano, Marco and Ehrlich, Ingo and H{\"o}cherl, Johannes and Gebbeken, Norbert}, title = {Investigation of fibre reinforced plastics with monolithic and hybrid stacking sequences under high-velocity impact loads}, 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}, 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{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{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{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} } @inproceedings{RomanoHoinkesEhrlichetal., author = {Romano, Marco and Hoinkes, Carl J. J. and Ehrlich, Ingo and H{\"o}cherl, Johannes and Gebbeken, Norbert}, title = {Influence of the impactor on the experimentally determined energy dissipation properties of fiber-reinforced plastics with hybrid layups under high velocity impact loads}, 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 = {650 -- 664}, language = {en} } @inproceedings{NiedernhuberEhrlichHoltmannspoetter, author = {Niedernhuber, Michal and Ehrlich, Ingo and Holtmannsp{\"o}tter, Jens}, title = {Fiber-Oriented Repair of Fiber Reinforced Plastics: Investigations on Tensile Specimens}, 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 = {298 -- 302}, 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{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{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} } @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{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 = {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{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{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} } @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 = {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} } @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} } @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} } @phdthesis{Ehrlich, author = {Ehrlich, Ingo}, title = {Impactverhalten schwach gekr{\"u}mmter Strukturen aus faserverst{\"a}rkten Kunststoffen}, address = {M{\"u}nchen}, language = {de} }