@misc{MaiwaldSchulzeSchmidtetal., author = {Maiwald, Frederik and Schulze, Julian and Schmidt, Michael and Hierl, Stefan}, title = {In-situ optical coherence tomography for spatio-temporal analysis of melt pool crystallization in absorber-free laser transmission welding of polymers}, series = {The 9th International Congress on Laser Advanced Materials Processing (LAMP2025), Ise-city, Mie-prefecture, Japan, June 10 to June 13, 2025}, journal = {The 9th International Congress on Laser Advanced Materials Processing (LAMP2025), Ise-city, Mie-prefecture, Japan, June 10 to June 13, 2025}, publisher = {Japan Laser Processing Society}, language = {en} } @article{HornbergerMarquisChristiansenetal., author = {Hornberger, Helga and Marquis, Peter M. and Christiansen, Silke H. and Albrecht, Manuel and Strunk, Horst P. and Franks, J.}, title = {Microstructure of a high strength alumina-glass composite combined with a diamond like carbon coating}, series = {Electron Microscopy and Analysis}, journal = {Electron Microscopy and Analysis}, doi = {10.1557/JMR.1996.0244}, pages = {559 -- 562}, abstract = {We investigate the mechanical and microstructural properties of a diamond-like carbon coating (DLC) which is deposited by plasma enhanced chemical vapor deposition (PECVD) onto an alumina/aluminosilicate glass composite used for biomedical applications. Ball-on-ring tests yield a fracture strength that is essentially influenced by the surface topology/roughness. The surface topology of the coating is investigated by atomic force microscopy (AFM). Tribology tests and nanoindentation represent the wear resistance and hardness; these are properties that are mainly influenced by the microstructural properties of the DLC coating. This microstructure is investigated by transmission electron microscopy (TEM) and analyzed by parallel electron energy loss spectroscopy (PEELS). For the general applicability of the coated composite, the interfacial adhesion of the DLC coating on the comparably rough substrate (roughness amplitudes and wavelengths are in the micrometer range) is important. Therefore, we focus on TEM investigations that show the interface to be free of gaps and pores that we, together with a characteristic microstructure adjacent to the interface, relate to the excellent adhesion. The interlayer consists of a high density of SiC grains, part of them directly bound to the substrate, and part of them bound to other SiC grains. This interlayer is followed by an essentially different region of the coating as concerns the microstructure; this region consists of nanocrystalline diamond particles embedded in an amorphous carbon matrix. It is this heterogeneous microstructure to which we attribute (i) the good adhesion based upon the interface stabilizing SiC grains, and (ii) the high hardness and wear resistance based upon the diamond nanocrystals in the coating.}, language = {en} } @article{ReindlMeisnerHierl, author = {Reindl, Thomas and Meisner, Dennis and Hierl, Stefan}, title = {Benchmarking of plastic-based Additive Manufacturing Processes}, series = {RTejournal - Forum f{\"u}r Rapid Technologie}, journal = {RTejournal - Forum f{\"u}r Rapid Technologie}, publisher = {Fachhochschule Aachen}, doi = {https://doi.org/10.58134/fh-aachen-rte_2023_002}, abstract = {Additive Manufacturing (AM) is a future-oriented manufacturing technology that is experiencing an enormous boom in the times of Industry 4.0. As a result, various AM technologies and printer models from different manufacturers are entering the market over a short time span. With the advancing establishment of this manufacturing technology for series applications, the expectations and requirements of the fabricated components are also increasing. However, a major challenge is the application-specific selection of the most suitable AM process due to a lack of comparable data. Furthermore, there needs to be more know-how regarding the geometrical and mechanical characteristics of AM parts. This paper addresses this problem by comparing the three most common plasticbased AM processes in the areas of surface quality, dimensional accuracy, and mechanical properties. Roughness measurements, evaluation of a benchmark artifact, tensile tests, and load increase tests are carried out. Based on the results, the individual possibilities and limitations of the compared AM processes can be detected.}, language = {en} } @inproceedings{Rill, author = {Rill, Georg}, title = {Real-Time capable Multibody Model of dual Truck Front Axles}, series = {Proceedings of DINAME 2023 - Selected Papers of the XIX International Symposium on Dynamic Problems of Mechanics, 26 Feb - 03 Mar 2023, Piren{\´o}polis, Brazil}, booktitle = {Proceedings of DINAME 2023 - Selected Papers of the XIX International Symposium on Dynamic Problems of Mechanics, 26 Feb - 03 Mar 2023, Piren{\´o}polis, Brazil}, editor = {Fleury, Agenor de T.}, publisher = {Springer}, abstract = {Dual front steering axles are quite common in multi-axled heavy duty trucks. In standard layouts of such axle combinations, the steer motions of the wheels depend not only on the rotation of the steering wheel but also on the movements of the axles. As a consequence, the model complexity of the steering system should match with the complexity of the suspension model. The development of new technologies like advanced driver assistance systems or autonomous driving can only be accomplished efficiently using extensive simulation methods. Such kind of applications demand for computationally efficient vehicle models. This paper presents a steering system model for dual front axles of heavy duty trucks which supplements the suspension model of the axles. The model takes the torsional compliance of the steering column as well as the stiffness of the tie rods and the coupling rod into account. A quasi-static solution provides a straight forward computation including the partial derivatives required for an efficient implicit solver. The steering system model matches perfectly with comparatively lean, but sufficiently accurate multibody suspension models.}, language = {en} } @inproceedings{MaiwaldKrothLaskinetal., author = {Maiwald, Frederik and Kroth, Lea and Laskin, Alexander and Hierl, Stefan and Schmidt, Michael}, title = {Enlarging the process window in absorber-free laser transmission welding of polymer foils using tailored laser intensity distribution}, series = {Procedia CIRP}, volume = {124}, booktitle = {Procedia CIRP}, publisher = {Elsevier}, doi = {10.1016/j.procir.2024.08.159}, pages = {489 -- 493}, abstract = {Absorber-free laser transmission welding enables precise and clean joining of polymer foils without absorbent additives or adhesives. It is well suited for applications in medical technology and food industry, which impose high demands on process reliability. To achieve a large process window and thus a reliable process, a homogeneous weld seam temperature is desirable. For this purpose, the intensity distribution of the laser beam is adapted locally by refractive beam shaping optics. Using a donut-shaped intensity distribution, the weld seam temperature is homogenized. Thus, the process window for welding polypropylene or polyethylene foils is enlarged up to a factor of 4 compared to a conventional, Gaussian-shaped distribution. This enables the reliable welding of even 85 µm thin foils, which could only be welded to a limited extent with a conventional laser intensity distribution.}, language = {en} } @inproceedings{SteiningerGadererDawoud, author = {Steininger, Peter and Gaderer, Matthias and Dawoud, Belal}, title = {Transient performance of a solar selective thermal insulation system}, series = {16th Advanced Building Skins Conference \& Expo, 21 - 22/10/2021, Bern, Switzerland}, booktitle = {16th Advanced Building Skins Conference \& Expo, 21 - 22/10/2021, Bern, Switzerland}, publisher = {Advanced Buidling Skins GmbH}, abstract = {A prototype of a thermal insulation system to offer high selectivity of the solar gain regarding the solar incidence angle (SATIS) was applied to a typical solid brick masonry for existing buildings in Germany. Light conducting elements (LCEs) inclined at 19 ° were incorporated in SATIS, which equals the average solar noon angle in southern Germany during winter. The entire wall construction was experimentally investigated in a differential climatic chamber test bench at four different irradiation angles according to a dynamic test procedure. In addition, a conventional wall construction (CWC) has been measured. At SATIS' design angle of 19 °, the SATIS wall construction shows a solar gain (SG) of 394.5 Wh/m², while the SG of the CWC amounts to only 25.4 Wh/m². The validated transient model of the SATIS wall construction showed that, at the end of the irradiation period of the dynamic test procedure (8 h), the solar heat penetrates to a depth of 253 mm and 111 mm inside the 385 mm thick brick wall masonry at the irradiation angles of 19 ° and 50 °, respectively. During the same time, the stored solar energy at 50 ° amounts to only 24.4 \% of that stored at 19 °.}, language = {en} } @inproceedings{SchaefferHerrmannBoehm, author = {Schaeffer, Leon and Herrmann, David and B{\"o}hm, Valter}, title = {Concept of a wrist Hand Orthosis based on a prestressed compliant structure}, series = {Proceedings of the 7th International Conference on Biomedical Engineering and Applications (ICBEA), Hangzhou, China, 21-23 April 2023}, booktitle = {Proceedings of the 7th International Conference on Biomedical Engineering and Applications (ICBEA), Hangzhou, China, 21-23 April 2023}, publisher = {IEEE}, doi = {10.1109/ICBEA58866.2023.00024}, pages = {98 -- 103}, abstract = {In the treatment of hand injuries in the context of orthopedic care, movable wrist hand orthoses are used in numerous instances. Early motion therapy is in most cases advantageous for adequate, rapid and successful long-term healing of the hand. Conventional dynamic wrist hand orthoses can only be used for movement therapy to a limited extent since they represent the wrist as a simple rotating joint and neglect the complexity of the hand movement possibilities. In this paper, a preliminary concept for dynamic wrist hand orthoses based on prestressed compliant structures is presented. The distinctive feature of this concept lies in the enabling of multiaxial motion capabilities of the human hand without applying conventional joints. According to the concept the wrist region is surrounded by a prestressed compliant structure. Besides the derivation and description of the concept, a first three-dimensional computer-aided design is shown. Additionally, the necessary steps in the development of such a novel dynamic wrist orthosis are discussed.}, language = {en} } @article{SalamaKouDawoudetal., author = {Salama, Amgad and Kou, Jisheng and Dawoud, Belal and Rady, Mohamed and El Morshedy, Salah}, title = {Investigation of the self-propulsion of a wetting/nonwetting ganglion in tapered capillaries with arbitrary viscosity and density contrasts}, series = {Colloids and Surfaces A: Physicochemical and Engineering Aspects}, volume = {664}, journal = {Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher = {Elsevier}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2023.131151}, abstract = {The movement of a meniscus inside a capillary tube has been extensively studied in the context of displacing one fluid with another immiscible one. This phenomenon exists in many applications including pharmaceutical, oil production, filtration and separation processes, and others. When one of the phases is entrapped inside a capillary tube, it forms what is called a ganglion with two menisci between the two fluids. In a straight uniform capillary tube, a stagnant entrapped ganglion is symmetric. The situation is different if the capillary tube is tapered in which case the two menisci assume different curvatures. Such inhomogeneity of the capillary pressure self-propels the ganglion to move. The fate of the ganglion inside the tapered tube depends on whether it is wetting or nonwetting to the tube wall. That is, after the initial movement, a wetting ganglion accelerates towards the tapered end of the tube while a nonwetting one decelerates towards the wider end before reaching a terminal configuration. Such fates are linked to the variations of the capillary pressure, which continuously increases for a wetting ganglion and decreases for the nonwetting one. In this work, a generalized model is developed that not only describes capillary-driven dynamics over a wide range of viscosity and density contrasts but also pressure-driven scenarios with/without gravity. The model, however, neglects the inertial effect of the two fluids on account of the fact that it is confined to the very early time of the movement process. A first-order nonlinear ordinary differential equation is developed that describes the dynamic behavior of both the wetting and nonwetting ganglions. A fourth-order Runge-Kutta algorithm is developed to solve the model equations. Furthermore, a computational fluid dynamics (CFD) analysis was used to provide a comparison and verification framework.}, 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} } @article{KeinerThomaBogdanovetal., author = {Keiner, Dominik and Thoma, Christian and Bogdanov, Dmitrii and Breyer, Christian}, title = {Seasonal hydrogen storage for residential on- and off-grid solar photovoltaics prosumer applications: Revolutionary solution or niche market for the energy transition until 2050?}, series = {Applied Energy}, volume = {340}, journal = {Applied Energy}, publisher = {Elsevier}, doi = {10.1016/j.apenergy.2023.121009}, pages = {17}, abstract = {Appropriate climate change mitigation requires solutions for all actors of the energy system. The residential sector is a major part of the energy system and solutions for the implementation of a seasonal hydrogen storage system in residential houses has been increasingly discussed. A global analysis of prosumer systems including seasonal hydrogen storage with water electrolyser, hydrogen compressor, storage tank, and a fuel cell studying the role of such a seasonal household storage in the upcoming decades is not available. This study aims to close this research gap via the improved LUT-PROSUME model, which models a fully micro sector coupled residential photovoltaic prosumer system with linear optimisation for 145 regions globally. The modelling of the cost development of hydrogen storage components allows for the simulation of a residential system from 2020 until 2050 in 5-year steps in hourly resolution. The systems are cost-optimised for either on- or off-grid operation in eight scenarios including battery electric vehicles, which can act as an additional vehicle-to-home electricity storage for the system. Results show that implementation of seasonal hydrogen systems only occurs in least cost solutions in high latitude countries when the system is forced to run in off-grid mode. In general, a solar photovoltaic plus battery system including technologies that can cover the heat demand is the most economic choice and can even achieve lower cost than a full grid supply in off-grid operation for most regions until 2050. Additional parameters including the self-consumption ratio, the demand cover ratio, and the heat cover ratio can therefore not be improved by seasonal storage systems if economics is the main deciding factor for a respective system. Further research opportunities and possible limitations of the system are then identified.}, language = {en} } @article{KuettnerRathsFischeretal., author = {Kuettner, Andreas and Raths, Max and Fischer, Samuel and Laumer, Tobias}, title = {Heat staking of polymer parts generated by fused layer modeling}, series = {The International Journal of Advanced Manufacturing Technology}, volume = {128}, journal = {The International Journal of Advanced Manufacturing Technology}, publisher = {Springer Nature}, doi = {10.1007/s00170-023-11850-y}, pages = {547 -- 562}, abstract = {Heat staking is a joining technology by which thermoplastic pins are formed by force and temperature to create a form- and force-fitting connection between components. This paper examines the characteristics of 3D printed pins in comparison to conventionally turned pins for heat staking applications. The 3D printed pins are created using fused layer modeling, with variations in horizontal and vertical building directions, as well as different layer thicknesses. The study investigates the impact of significant factors on the heat staking process, including the forming force and temperature. Tensile tests, micrographs, and micro-CT measurements were conducted to determine the properties of the heat-staked joints. Additionally, a stage plan was developed to enhance the understanding of the forming process of both printed and conventionally turned materials. The findings suggest that, under specific process parameters, 3D printed pins exhibit comparable strength to conventionally manufactured pins. The research also demonstrates that the anisotropy resulting from the layer-by-layer construction of the pins significantly influences the strength of the connection. Furthermore, the study reveals that 3D printed pins exhibit good forming accuracy during the heat staking process, and the cavities formed during printing can be substantially reduced.}, language = {en} } @misc{MaiwaldHierl, author = {Maiwald, Frederik and Hierl, Stefan}, title = {Laser welding device for clamping and welding components and method for clamping and welding components}, organization = {Ostbayerische Technische Hochschule Regensburg}, language = {en} } @inproceedings{SchorrEbnetZimmermannetal., author = {Schorr, Philipp and Ebnet, Markus and Zimmermann, Klaus and B{\"o}hm, Valter}, title = {Dynamic Investigation of a Rolling Locomotion System Based on a Tensegrity Structure with Spatially Curved Compressed Members}, series = {Perspectives in Dynamical Systems I Applications : DSTA Ł{\´o}d{\'{z}} Poland December 6 - 9 2021. - (Springer Proceedings in Mathematics \& Statistics ; Bd. 453)}, booktitle = {Perspectives in Dynamical Systems I Applications : DSTA Ł{\´o}d{\'{z}} Poland December 6 - 9 2021. - (Springer Proceedings in Mathematics \& Statistics ; Bd. 453)}, editor = {Awrejcewicz, Jan}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-031-56491-8}, doi = {10.1007/978-3-031-56492-5_32}, pages = {437 -- 449}, abstract = {In this paper a compliant tensegrity structure based on spatially curved compressed members is presented. Due to an internal variation of the prestress state the shape of the structure can be controlled. In particular, a modification of a cylindrical outer shape to a conical form is achieved. Regarding to the applications in mobile robotics this approach enables a steerable two-dimensional rolling locomotion system. Beside the consideration of the underlying non-holonomic constraints a simplified mechanical model an the corresponding equations of motion are derived for a predefined actuation principle. Various numerical simulations are evaluated focusing on the corresponding locomotion behavior. Based on these results a reliable actuation strategy to navigate in two dimensions is proposed.}, language = {en} } @inproceedings{HerrmannSchaefferLehmannetal., author = {Herrmann, David and Schaeffer, Leon and Lehmann, Lukas and Busch, Tobias and B{\"o}hm, Valter}, title = {Preliminary Theoretical Considerations on 2D Multistable Tensegrity Structures Based on Equilateral Triangles}, series = {New trends in mechanism and machine science: Proceedings of EuCoMeS 2024}, booktitle = {New trends in mechanism and machine science: Proceedings of EuCoMeS 2024}, editor = {Rosati, Giulio and Gasparetto, Alessandro and Ceccarelli, Marco}, publisher = {Springer}, address = {Cham}, isbn = {978-3-031-67294-1}, doi = {10.1007/978-3-031-67295-8_21}, pages = {183 -- 191}, language = {en} } @article{HimmeleinPerezRuizdeGaribayBrandeletal., author = {Himmelein, Susanne and Perez Ruiz de Garibay, Aritz and Brandel, Veronika and Zierfuß, Frank and Bingold, Tobias Michael}, title = {The ADVanced Organ Support (ADVOS) hemodialysis system removes IL-6: an in vitro proof-of-concept study}, series = {Intensive care medicine experimental}, volume = {12}, journal = {Intensive care medicine experimental}, number = {1}, publisher = {SpringerOpen}, address = {Berlin ; Heidelberg}, issn = {2197-425X}, doi = {10.1186/s40635-024-00652-5}, abstract = {BACKGROUND IL-6 is a pleiotropic cytokine modulating inflammation and metabolic pathways. Its proinflammatory effect plays a significant role in organ failure pathogenesis, commonly elevated in systemic inflammatory conditions. Extracorporeal blood purification devices, such as the Advanced Organ Support (ADVOS) multi hemodialysis system, might offer potential in mitigating IL-6's detrimental effects, yet its efficacy remains unreported. METHODS We conducted a proof-of-concept in vitro study to assess the ADVOS multi system's efficacy in eliminating IL-6. Varying concentrations of IL-6 were introduced into a swine blood model and treated with ADVOS multi for up to 12 h, employing different blood and concentrate flow rates. IL-6 reduction rate, clearance, and dynamics in blood and dialysate were analyzed. RESULTS IL-6 clearance rates of 0.70 L/h and 0.42 L/h were observed in 4 and 12-h experiments, respectively. No significant differences were noted across different initial concentrations. Reduction rates ranged between 40 and 46\% within the first 4 h, increasing up to 72\% over 12 h, with minimal impact from flow rate variations. Our findings suggest that an IL-6-albumin interaction and convective filtration are implicated in in vitro IL-6 elimination with ADVOS multi. CONCLUSIONS This study demonstrates for the first time an efficient and continuous in vitro removal of IL-6 by ADVOS multi at low blood flow rates. Initial concentration-dependent removal transitions to more consistent elimination over time. Further clinical investigations are imperative for comprehensive data acquisition.}, language = {en} } @article{UhrhanSchwindtWitte, author = {Uhrhan, Katja and Schwindt, Esther and Witte, Hartmut}, title = {Fabrication and Dielectric Validation of an Arm Phantom for Electromyostimulation}, series = {Bioengineering}, volume = {11}, journal = {Bioengineering}, number = {7}, publisher = {MDPI}, address = {Basel}, issn = {2306-5354}, doi = {10.3390/bioengineering11070724}, abstract = {Electromyostimulation (EMS) is an up-and-coming training method that demands further fundamental research regarding its safety and efficacy. To investigate the influence of different stimulation parameters, electrode positions and electrode sizes on the resulting voltage in the tissue, a tissue mimicking phantom is needed. Therefore, this study describes the fabrication of a hydrogel arm phantom for EMS applications with the tissue layers of skin, fat, blood and muscle. The phantom was dielectrically validated in the frequency range of 20 Hz to 100 Hz. We also conducted electromyography (EMG) recordings during EMS on the phantom and compared them with the same measurements on a human arm. The phantom reproduces the dielectric properties of the tissues with deviations ranging from 0.8\% to more than 100\%. Although we found it difficult to find a compromise between mimicking the permittivity and electrical conductivity at the same time, the EMS-EMG measurements showed similar waveforms (1.9-9.5\% deviation) in the phantom and human. Our research contributes to the field of dielectric tissue phantoms, as it proposes a multilayer arm phantom for EMS applications. Consequently, the phantom can be used for initial EMS investigations, but future research should focus on further improving the dielectric properties.}, language = {en} } @inproceedings{MaiwaldFriesSchulzeetal., author = {Maiwald, Frederik and Fries, Fabian and Schulze, Julian and Honnerov{\´a}, Petra and Hierl, Stefan and Schmidt, Michael}, title = {Optical coherence tomography for in situ weld seam monitoring in absorber-free laser transmission welding}, series = {Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXX, 25-31 January 2025, San Francisco, California, United States}, booktitle = {Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXX, 25-31 January 2025, San Francisco, California, United States}, publisher = {SPIE}, doi = {10.1117/12.3040607}, abstract = {Optical and medical devices are frequently made of polymers and place high demands on precision, cleanliness, and reliability of the manufacturing processes used. Absorber-free laser transmission welding is well-suited for joining these devices: the energy input is contactless, no adhesives, additives, or absorbers are required, and the fiber lasers used enable precise weld seams. As the weld seam geometry is decisive for the joint strength and thus crucial for the quality of the product, the welding process is monitored in-situ using Optical Coherence Tomography (OCT). Subsequently, the weld seam geometry is identified automatically using the AI model "Segment Anything" (SAM), which performs semantic segmentation of the OCT data without requiring any training from the user. Welding tests using polyamide six indicate that the seam size is measured with an accuracy of a few hundredths of a millimeter, showing excellent agreement with microscopic images of microtome sections.}, language = {en} } @article{ChristiansenAlbrechtStrunketal., author = {Christiansen, Silke H. and Albrecht, Manuel and Strunk, Horst P. and Hornberger, Helga and Marquis, Peter M. and Franks, J.}, title = {Mechanical properties and microstructural analysis of a diamond-like carbon coating on an alumina/glass composite}, series = {Journal of Materials Research}, volume = {11}, journal = {Journal of Materials Research}, number = {8}, doi = {10.1557/JMR.1996.0244}, pages = {1934 -- 1942}, abstract = {We investigate the mechanical and microstructural properties of a diamond-like carbon coating (DLC) which is deposited by plasma enhanced chemical vapor deposition (PECVD) onto an alumina/aluminosilicate glass composite used for biomedical applications. Ball-on-ring tests yield a fracture strength that is essentially influenced by the surface topology/roughness. The surface topology of the coating is investigated by atomic force microscopy (AFM). Tribology tests and nanoindentation represent the wear resistance and hardness; these are properties that are mainly influenced by the microstructural properties of the DLC coating. This microstructure is investigated by transmission electron microscopy (TEM) and analyzed by parallel electron energy loss spectroscopy (PEELS). For the general applicability of the coated composite, the interfacial adhesion of the DLC coating on the comparably rough substrate (roughness amplitudes and wavelengths are in the micrometer range) is important. Therefore, we focus on TEM investigations that show the interface to be free of gaps and pores that we, together with a characteristic microstructure adjacent to the interface, relate to the excellent adhesion. The interlayer consists of a high density of SiC grains, part of them directly bound to the substrate, and part of them bound to other SiC grains. This interlayer is followed by an essentially different region of the coating as concerns the microstructure; this region consists of nanocrystalline diamond particles embedded in an amorphous carbon matrix. It is this heterogeneous microstructure to which we attribute (i) the good adhesion based upon the interface stabilizing SiC grains, and (ii) the high hardness and wear resistance based upon the diamond nanocrystals in the coating.}, language = {en} } @article{KloiberSchultheissSoteloetal., author = {Kloiber, Jessica and Schultheiß, Ulrich and Sotelo, Lamborghini and Sarau, George and Christiansen, Silke H. and Gavras, Sarkis and Hort, Norbert and Hornberger, Helga}, title = {Corrosion behaviour of electropolished magnesium materials}, series = {Materials Today Communications}, journal = {Materials Today Communications}, edition = {Journal Pre-proof}, publisher = {Elsevier}, doi = {10.1016/j.mtcomm.2023.107983}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-68254}, abstract = {Although magnesium and its alloys are promising candidates as biodegradable implant materials, the tendency for localized corrosion mechanism in physiological environment limit their biomedical application. Electropolishing is an attractive strategy for improving the corrosion behaviour of metals, but it is still largely unexplored in magnesium materials. In this study, the characterization of electropolished surfaces of AM50 and pure magnesium was performed, focussing on their in vitro degradation behaviour in cell medium. Corrosion rates were evaluated using potentiodynamic polarisation. The surface morphology before and after the onset of corrosion was investigated by scanning electron microscopy and confocal laser scanning microscopy. The presented electropolishing process led to improved surface performances, observable by significantly lower corrosion rates (0.08 mm·year-1 in Dulbecco's modified Eagle's medium), lower arithmetical mean height (0.05 µm), lower water contact angle (25-35°) and lower micro hardness (35-50 HV 0.1) compared to mechanically and chemically treated surfaces. MgO/Mg(OH)2 could be detected on electropolished surfaces. The localized corrosion mode could be reduced, but not entirely prevented. Electropolishing shows great potential as post-treatment of magnesium-based components, but detailed tests of the long-term corrosion behaviour are an important area of future research.}, language = {en} } @article{ChavezVegaBoehmBeckeretal., author = {Chavez Vega, Jhohan Harvey and B{\"o}hm, Valter and Becker, Tatiana I. and Gast, Simon and Zeidis, Igor and Zimmermann, Klaus}, title = {Actuators based on a controlled particle-matrix interaction in magnetic hybrid materials for applications in locomotion and manipulation systems}, series = {Physical Sciences Reviews}, volume = {7}, journal = {Physical Sciences Reviews}, number = {11}, publisher = {de Gruyter}, doi = {10.1515/psr-2019-0087}, pages = {1263 -- 1290}, abstract = {The paper deals with the investigation of magneto-sensitive elastomers (MSE) and their application in technical actuator systems. MSE consist of an elastic matrix containing suspended magnetically soft and/or hard particles. Additionally, they can also contain silicone oil, graphite particles, thermoplastic components, etc., in various concentrations in order to tune specific properties such as viscosity, conductivity and thermoelasticity, respectively. The focuses of investigations are the beneficial properties of MSE in prototypes for locomotion and manipulation purposes that possess an integrated sensor function. The research follows the principle of a model-based design, i.e. the working steps are ideation, mathematical modelling, material characterization as well as building first functional models (prototypes). The developed apedal (without legs) and non-wheeled locomotion systems use the interplay between material deformations and the mechanical motion in connection with the issues of control and stability. Non-linear friction phenomena lead to a monotonous forward motion of the systems. The aim of this study is the design of such mechanical structures, which reduce the control costs. The investigations deal with the movement and control of 'intelligent' mechanisms, for which the magnetically field-controlled particle-matrix interactions provide an appropriate approach. The presented grippers enclose partially gripped objects, which is an advantage for handling sensitive objects. Form-fit grippers with adaptable contour at the contact area enable a uniform pressure distribution on the surface of gripped objects. Furthermore, with the possibility of active shape adaptation, objects with significantly differing geometries can be gripped. To realise the desired active shape adaptation, the effect of field-induced plasticity of MSE is used. The first developed prototypes mainly confirm the functional principles as such without direct application. For this, besides the ability of locomotion and manipulation itself, further technological possibilities have to be added to the systems. The first steps are therefore being taken towards integrated MSE based adaptive sensor systems.}, language = {en} } @article{ChavezVegaSchorrKaufholdetal., author = {Chavez Vega, Jhohan Harvey and Schorr, Philipp and Kaufhold, Tobias and Zentner, Lena and Zimmermann, Klaus and B{\"o}hm, Valter}, title = {Influence of Elastomeric Tensioned Members on the Characteristics of Compliant Tensegrity Structures in Soft Robotic Applications}, series = {Procedia Manufacturing}, volume = {52}, journal = {Procedia Manufacturing}, publisher = {Elsevier}, issn = {2351-9789}, doi = {10.1016/j.promfg.2020.11.048}, pages = {289 -- 294}, abstract = {The use of mechanically prestressed compliant structures in soft robotics is a recently discussed topic. Tensegrity structures, consisting of a set of rigid disconnected compressed members connected to a continuous net of prestressed elastic tensioned members build one specific class of these structures. Robots based on these structures have manifold shape changing abilities and can adapt their mechanical properties reversibly by changing of their prestress state according to specific tasks. In the paper selected aspects on the potential use of elastomer materials in these structures are discussed with the help of theoretical analysis. Therefore, a selected basic tensegrity structure with elastomer members is investigated focusing on the stiffness and shape changing ability in dependence of the nonlinear hyperelastic behavior of the used elastomer materials. The considered structure is compared with a conventional tensegrity structure with linear elastic tensioned members. Finally, selected criterions for the advantageous use of elastomer materials in compliant tensegrity robots are discussed.}, language = {en} } @article{SchorrChavezVegaZentneretal., author = {Schorr, Philipp and Chavez Vega, Jhohan Harvey and Zentner, Lena and B{\"o}hm, Valter}, title = {Reconfiguration of planar quadrilateral linkages utilizing the tensegrity principle}, series = {Mechanism and machine theory}, journal = {Mechanism and machine theory}, number = {156}, publisher = {Elsevier}, doi = {10.1016/j.mechmachtheory.2020.104172}, abstract = {The development of reconfigurable planar four-bar linkages by applying the tensegrity principle is considered. Conventional quadrilateral linkages enable two operation modes differing in the kinematic behavior. However, a change between these states is not possible due to the geometric constraints. To enable a reconfiguration between the different modes one-sided limited nonholonomic constraints are introduced in this work. This issue is realized by applying ropes that cannot resist compression. However, to guarantee an appropriate load case in operation a prestress within the mechanism is required. Hence, the linkage is extended to a tensegrity-based mechanism. The structural dynamics are derived using the LAGRANGE formalism and the structural behavior is evaluated using numerical simulations. Furthermore, a prototype of an exemplary tensegrity-based mechanism is manufactured and experiments regarding the mechanical properties, in particular the reconfiguration, are performed. The results suggest the potential benefit of applying the tensegrity principle within conventional planar four-bar linkages.}, language = {en} } @article{ChavezVegaZiolkowskiSchorretal., author = {Chavez Vega, Jhohan Harvey and Ziolkowski, Marek and Schorr, Philipp and Spiess, Lothar and B{\"o}hm, Valter and Zimmermann, Klaus}, title = {A method to approach constant isotropic permeabilities and demagnetization factors of magneto-rheological elastomers}, series = {Journal of Magnetism and Magnetic Materials}, volume = {527}, journal = {Journal of Magnetism and Magnetic Materials}, publisher = {Elsevier}, doi = {10.1016/j.jmmm.2021.167742}, abstract = {The use of non-conventional materials is nowadays of much interest in scientific community. Magneto-rheological elastomers are hybrid materials, which in presence of magnetic fields state a change in their mechanical properties. They are composed by an elastomeric matrix with embedded magnetic particles. One of the most attractive features of these materials is that as soon as the magnetic field is removed from the material, the original mechanical properties are completely recovered, with negligible differences in comparison to the original state. This paper focuses on the study of magnetic characteristics of these smart materials, such as relative permeability and demagnetizing factors, for samples with different volume concentration of ferromagnetic particles.}, language = {en} } @inproceedings{BoehmSchorrFeldmeieretal., author = {B{\"o}hm, Valter and Schorr, Philipp and Feldmeier, T. and Chavez Vega, Jhohan Harvey and Henning, S. and Zimmermann, Klaus and Zentner, Lena}, title = {An Approach to Robotic End Effectors Based on Multistable Tensegrity Structures}, series = {New Trends in Mechanism and Machine Science: 8th European Conference on Mechanism Science (EuCoMeS), 2020}, booktitle = {New Trends in Mechanism and Machine Science: 8th European Conference on Mechanism Science (EuCoMeS), 2020}, publisher = {Springer}, doi = {10.1007/978-3-030-55061-5_53}, pages = {470 -- 478}, abstract = {In this paper compliant multistable tensegrity structures with discrete variable stiffness are investigated. The different stiffness states result from the different prestress states of these structures corresponding to the equilibrium configurations. Three planar tensegrity mechanisms with two stable equilibrium configurations are considered exemplarily. The overall stiffness of these structures is characterized by investigations with regard to their geometric nonlinear static behavior. Dynamical analyses show the possibility of the change between the equilibrium configurations and enable the derivation of suitable actuation strategies.}, language = {en} } @misc{ChavezVegaHenningZentneretal., author = {Chavez Vega, Jhohan Harvey and Henning, S. and Zentner, Lena and B{\"o}hm, Valter}, title = {Soft tensegrity structures with variable stiffness and shape changing ability}, series = {Annual Meeting of the DFG Priority Programme Soft Material Robotic Systems, SPP2100, 02-04. M{\"a}rz 2020, Schneverdingen}, journal = {Annual Meeting of the DFG Priority Programme Soft Material Robotic Systems, SPP2100, 02-04. M{\"a}rz 2020, Schneverdingen}, language = {en} } @article{BeckerBoehmChavezVegaetal., author = {Becker, Tatiana I. and B{\"o}hm, Valter and Chavez Vega, Jhohan Harvey and Odenbach, Stefan and Raikher, Yuriy L. and Zimmermann, Klaus}, title = {Magnetic-field-controlled mechanical behavior of magneto-sensitive elastomers in applications for actuator and sensor systems}, series = {Archive of Applied Mechanics}, volume = {89}, journal = {Archive of Applied Mechanics}, number = {1}, publisher = {Springer Nature}, doi = {10.1007/s00419-018-1477-4}, pages = {133 -- 152}, abstract = {The development of actuator and sensor systems with complex adaptive behavior and operating sensitivity is one of the actual scientific challenges. Smart materials like magneto-sensitive elastomers (MSEs) offer great potential for designing such intelligent devices, because they possess unique magnetic-field-dependent properties. The present paper deals with investigations of the free and forced vibrational behavior displayed by cantilever beams of MSEs containing magnetically soft particles in a uniform magnetic field. It is shown experimentally as well as theoretically that the first bending eigenfrequency of MSE beams depends strongly on the strength of an applied magnetic field. The proposed magneto-mechanical model is based on the vibrational dynamics of thin rods and predicts reliably the amplitude-frequency characteristics depending on the geometric configuration of the MSE and its material parameters. It is found that the vibration response of an MSE beam under kinematic excitation of its base can be modified indirectly by a magnetic field control due to the change of the vibration characteristics. As a result, the resonance can occur in different ranges of the excitation frequency. The dependencies of the amplification ratio on the excitation frequency are obtained experimentally and compared with the result provided by the theoretical model. Moreover, investigations on the potential use of the field-induced plasticity effect of MSEs in form-fit gripper applications are presented. This effect can be used to realize shape adaptable system parts. It is found that the mechanical properties of each component and its concentration within the mixture have an impact on the mechanical behavior of the whole MSE compound. Such parameters as the strength of magnetic field and geometry of the MSE sample have influence on the quality of shape adaptation. The evidence presented provides a good basis for the realization of MSE-based actuator and sensor systems with adaptable sensitivity.}, language = {en} } @article{PremChavezVegaBoehmetal., author = {Prem, Nina and Chavez Vega, Jhohan Harvey and B{\"o}hm, Valter and Sindersberger, Dirk and Monkman, Gareth J. and Zimmermann, Klaus}, title = {Properties of Polydimethylsiloxane and Magnetoactive Polymers with Electroconductive Particles}, series = {Macromolecular Chemistry and Physics}, volume = {219}, journal = {Macromolecular Chemistry and Physics}, number = {18}, publisher = {Wiley}, doi = {10.1002/macp.201800222}, abstract = {Magnetoactive polymers are intelligent materials whose mechanical and electrical characteristics are reversibly influenced by external magnetic stimuli. They consist of a highly elastic polymer matrix in which magnetically soft and/or hard particles are distributed by means of special fabrication processes. In addition to ferromagnetic particles such as carbonyl iron powder, electrically conductive particles may also be embedded into the polymer matrix. After characterizing a range of compounds, this work focuses on a comparison of the electrical properties and the suitability of various materials for applications, with particular emphasis on integration into 3D and 6D printing processes. 6D printing is based on the selective positioning of particles in a 3D polymer matrix with a further three degrees of freedom for a graduated dispersion of the particles at certain points and in desired directions. The aim is therefore to ensure that the polymers containing electroconductive tracks have the best possible electrical properties, that is, low resistivity but are still capable of being printed. A comparison between the traditionally used compounds containing graphite and carbon black is made for the first time. This latter is found to be greatly superior both in terms of electrical conductivity and applicability to 3D printing and 6D printing.}, language = {en} } @inproceedings{ChavezVegaSchorrScharffetal., author = {Chavez Vega, Jhohan Harvey and Schorr, Philipp and Scharff, Moritz and Schale, Florian and B{\"o}hm, Valter and Zimmermann, Klaus}, title = {Towards Magneto-Sensitive Elastomers Based End-Effectors for Gripping Application Technologies}, series = {2019 IEEE International Conference on Mechatronics (ICM), 18-20 March 2019, Ilmenau, Germany}, volume = {1}, booktitle = {2019 IEEE International Conference on Mechatronics (ICM), 18-20 March 2019, Ilmenau, Germany}, publisher = {IEEE}, doi = {10.1109/ICMECH.2019.8722922}, pages = {217 -- 222}, abstract = {Nowadays, the demands in engineering systems become more challenging and the use of conventional materials for certain applications is not suitable. This issue encourages the investigation of novel and innovative materials in soft robotics field. A promising approach is the consideration of magneto-sensitive elastomers (MSE). These materials enable a useful adaptability responding to their mechanical properties. By applying a static magnetic field, the static and dynamic characteristics can be tuned. However, currently the knowledge about the correlations are not satisfying and the resulting material properties can only be predicted approximately with the use of time-expensive simulations regarding to the nano scale. Therefore, feasible material simulations of the description of the mechanical behavior are necessary. In this paper experimental studies of the influence of a static magnetic field on the mechanical properties and shape adaptability of MSE are presented. Furthermore, based on these results a simulation for the material behavior is executed. These results can be implemented into further simulations for various MSE exemplars.}, language = {en} } @inproceedings{SchorrChavezVegaZentneretal., author = {Schorr, Philipp and Chavez Vega, Jhohan Harvey and Zentner, Lena and B{\"o}hm, Valter}, title = {Reconfigurable Planar Quadrilateral Linkages Based on the Tensegrity Principle}, series = {Microactuators, Microsensors and Micromechanisms, MAMM, 2020}, booktitle = {Microactuators, Microsensors and Micromechanisms, MAMM, 2020}, editor = {Zentner, Lena and Strehle, Steffen}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-030-61651-9}, doi = {10.1007/978-3-030-61652-6_5}, pages = {48 -- 57}, abstract = {A feasible possibility to develop planar reconfigurable mechanisms is introduced in this work. Applying the tensegrity principle to common four-bar linkages allows a controllable change between two configurations of the mechanism. These two states correspond to different working spaces which vary regarding to the kinematic and mechanical properties. Therefore, the reconfiguration of the mechanism enables two different operation modes. Hence, this kind of mechanism enables the advantageous properties of conventional linkages with an additional enhanced adaptability of the kinematic and mechanic behavior. Beside the conceptual design of such tensegrity-based mechanisms, a reconfigurable four-bar parallel linkage is considered exemplarily. Numerical simulations are evaluated focusing on the kinematic behavior and the structural mechanics of this mechanism. Especially the reconfiguration of the mechanism by changing between two different working spaces is considered. The simulation results clarify the benefit of utilizing the tensegrity principle in mechanism theory. Adding only a few members to the original linkage enables a reconfigurable mechanism with comparable complexity.}, language = {en} } @incollection{ChavezVegaBoehmBeckeretal., author = {Chavez Vega, Jhohan Harvey and B{\"o}hm, Valter and Becker, Tatiana I. and Gast, Simon and Zeidis, Igor and Zimmermann, Klaus}, title = {Actuators based on a controlled particlematrix interaction in magnetic hybrid materials for applications in locomotion and manipulation systems}, series = {Magnetic Hybrid-Materials: Multi-scale modelling synthesis and applications}, booktitle = {Magnetic Hybrid-Materials: Multi-scale modelling synthesis and applications}, editor = {Odenbach, Stefan}, publisher = {De Gruyter}, address = {Berlin}, isbn = {9783110569636}, doi = {10.1515/9783110569636-027}, pages = {653 -- 680}, abstract = {The paper deals with the investigation of magneto-sensitive elastomers(MSE) and their application in technical actuator systems. MSE consist of an elasticmatrix containing suspended magnetically soft and/or hard particles. Additionally,they can also contain silicone oil, graphite particles, thermoplastic components, etc.,in various concentrations in order to tune specific properties such as viscosity, con-ductivity and thermoelasticity, respectively. The focuses of investigations are thebeneficial properties of MSE in prototypes for locomotion and manipulation purposesthat possess an integrated sensor function. The research follows the principle of amodel-based design, i.e. the working steps are ideation, mathematical modelling,material characterization as well as building first functional models (prototypes). Thedeveloped apedal (without legs) and non-wheeled locomotion systems use the inter-play between material deformations and the mechanical motion in connection with theissues of control and stability. Non-linear friction phenomena lead to a monotonousforward motion of the systems. The aim of this study is the design of such mechanicalstructures, which reduce the control costs. The investigations deal with the movementand control of'intelligent'mechanisms, for which the magnetically field-controlledparticle-matrix interactions provide an appropriate approach. The presented grippersenclose partially gripped objects, which is an advantage for handling sensitive objects.Form-fit grippers with adaptable contour at the contact area enable a uniform pressuredistribution on the surface of gripped objects. Furthermore, with the possibility ofactive shape adaptation, objects with significantly differing geometries can be gripped.To realise the desired active shape adaptation, the effect of field-induced plasticity ofMSE is used. The first developed prototypes mainly confirm the functional principles assuch without direct application. For this, besides the ability of locomotion andmanipulation itself, further technological possibilities have to be added to the systems.}, 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{BartschBehamGebhardtetal., author = {Bartsch, Alexander and Beham, Daniela and Gebhardt, Jakob and Ehrlich, Ingo and Schratzenstaller, Thomas and Monkman, Gareth J.}, title = {Mechanical Properties of NdPrFeB Based Magnetoactive Bisphenol-Free Boron-Silicate Polymers}, series = {Journal of Nanomedicine and Nanotechnology}, volume = {14}, journal = {Journal of Nanomedicine and Nanotechnology}, number = {6}, publisher = {Walsh Medical Media}, issn = {2157-7439}, doi = {10.35248/2157-7439.23.14.705}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-67425}, abstract = {Following a ban on many materials containing bisphenol-A, new bisphenol-free Boron silicates have been found as substitutes. The purpose of this study is to describe the mechanical properties of these bisphenol-free magnetoactive borosilicate polymers containing hard magnetic particles. Samples of 0\%, 33\% and 66\% by wt. were loaded for compression using a universal testing machine. The maximum forces occurring for different travel speeds were compared before and after post-magnetization treatments. The post-magnetization included 2 stages. In addition, the change in mechanical properties within 24 hours after the post-magnetization process was investigated. Furthermore, the influence of speed and particle content were investigated. In general, there is a correlation between the required compressive force and, the level of post-magnetization stress, the increase in travel speed and particle content in the boron silicate. Comparison of the non-post-magnetized and post-magnetized samples using two-tailed t-tests shows that the p-values for all weight fraction changes in NdPrFeB particles and travel speeds are less than 0.001. Also, a comparison between tests in which the traverse speed was varied also showed significant changes in the resulting compression forces. The same is valid for changes in the weight ratio of the NdPrFeB particles in the samples. For post-magnetized samples, no significant difference can be observed in the first 24 hours following magnetization. In summary, the material presents viscoelastic, plastic force-displacement behavior, which can be well recognized by its bi-linear curve shape. The investigation shows that borosilicate polymers based on NdPrFeB can have their mechanical behavior modified and controlled by post-magnetization processes. This opens new possibilities for many future applications.}, language = {en} } @inproceedings{SchaefferHerrmannBoehm, author = {Schaeffer, Leon and Herrmann, David and B{\"o}hm, Valter}, title = {Preliminary theoretical considerations of a hand orthosis based on a prestressed, compliant structure}, series = {Proceedings of the 2023 International Symposium on Medical Robotics (ISMR), Atlanta, 19-21 April 2023}, booktitle = {Proceedings of the 2023 International Symposium on Medical Robotics (ISMR), Atlanta, 19-21 April 2023}, publisher = {IEEE}, doi = {10.1109/ISMR57123.2023.10130230}, pages = {1 -- 7}, abstract = {In the treatment of hand injuries in the context of orthopedic care, movable hand orthoses are used in many cases. Early motion therapy is in most cases advantageous for adequate, rapid, and successful long-term healing of the hand. Conventional mobile hand orthoses can only be used for movement therapy to a limited extent since they represent the wrist as a simple rotating joint and neglect the complexity of the movement possibilities of the hand. In this paper, a novel concept for movable hand orthoses based on prestressed compliant structures is presented. The advantage with this concept is that it replicates the multiaxial motion capabilities without the need for conventional joints. Besides the derivation and description of the concept, a first three-dimensional CAD design is shown. Additionally, the next planned steps in the development of such a novel dynamic hand orthosis are described.}, language = {en} } @inproceedings{GerschSchulz, author = {Gersch, Sebastian and Schulz, Carsten}, title = {Realpotential von Eigenspannungen zur Erh{\"o}hung der Bauteillebensdauer bei generativ gefertigten, dynamisch beanspruchten Bauteilen}, series = {Dresdner Maschinenelemente Kolloquium - DMK 2022, 26.-27. April / Technische Universit{\"a}t Dresden}, booktitle = {Dresdner Maschinenelemente Kolloquium - DMK 2022, 26.-27. April / Technische Universit{\"a}t Dresden}, publisher = {sierke Verlag}, address = {G{\"o}ttingen}, isbn = {978-3-96548-135-0}, pages = {496 -- 505}, language = {de} } @inproceedings{JudenmannHoltmannspoetterEhrlich, author = {Judenmann, Anna and Holtmannsp{\"o}tter, Jens and Ehrlich, Ingo}, title = {Additive Manufacturing of Continuous Fiber-Reinforced Composites}, series = {Proceedings of the Munich Symposium on Lightweight Design 2022}, booktitle = {Proceedings of the Munich Symposium on Lightweight Design 2022}, language = {de} } @incollection{AltenbergerNosterScholtesetal., author = {Altenberger, Igor and Noster, Ulf and Scholtes, Berthold and Ritchie, Robert O.}, title = {High Temperature Fatigue of Mechanically Surface Treated Materials}, series = {Shot peening}, booktitle = {Shot peening}, editor = {Wagner, Lothar}, publisher = {Wiley-VCH}, address = {Weinheim; [Cambridge]}, isbn = {9783527606580}, doi = {10.1002/3527606580.ch62}, pages = {483 -- 489}, abstract = {Introduction The most well known effect of mechanical surface treatments on metallic materials is the improvement in fatigue properties. It is therefore not surprising that most of the archival literature on mechanical surface treatments, such as shot peening, deep rolling and laser shock peening, deals with the effect of near-surface properties on fatigue behavior. Most of these studies, however, are confined to room temperature fatigue behavior; in comparision, the effect of mechanical surface treatment on fatigue behavior at high temperatures has been rarely investigated [1-5]. The reason for this disparity can be found in the popular belief that fatigue strength improvement by mechanical surface treatments is mainly due to the presence of compressive residual stresses, and since such stresses should anneal out at elevated temperatures, mechanical surface treatments for high temperature applications would appear questionable. However, this view may be over simplistic as there is always a possibility that the residual stresses may be at least partially stable at elevated temperatures [6]; in addition, other factors may be involved, such as the nature of the near-surface microstructure. Accordingly, it is the objective of this study to examine the role of mechanical surface treatments on the high temperature fatigue behavior of several metallic engineering materials. Moreover, it is the aim of this work to clarify what are the critical temperature "thresholds' at which near-surface microstructures and residual stresses become unstable and whether this can explain the observed fatigue behavior.}, language = {en} } @book{AltenbergerWagnerMhaedeetal., author = {Altenberger, Igor and Wagner, Lothar and Mhaede, Mansour and Juijerm, Patiphan and Noster, Ulf}, title = {Effect of Deep Rolling on the Cyclic Performance of Magnesium and Aluminium Alloys in the Temperature Range 20-250°C}, series = {The 10th International Conference on Shot Peening (ICSP), Conference Proceedings, Tokyo Japan, 15th to 18th September, 2008}, journal = {The 10th International Conference on Shot Peening (ICSP), Conference Proceedings, Tokyo Japan, 15th to 18th September, 2008}, abstract = {Mechanical surface treatments such as deep rolling or laser-shock peening can markedly affect the cyclic performance of light-weight alloys, especially if significant thick work hardened surface regions are induced. At room temperature, the cyclic deformation behaviour is strongly influenced by the nature of the induced near-surface microstructures provided that they remain stable during fatigue loading. At elevated temperatures, the stability of near-surface work hardening and local microstructures plays an even more important role since the process-induced residual compressive stresses are likely to anneal out partially or completely. This overview illustrates to what extent deep rolling can effect the cyclic performance of various wrought light alloys being fatigue loaded in stress control at ambient and elevated temperatures.}, language = {en} } @incollection{NosterAltenbergerRitchieetal., author = {Noster, Ulf and Altenberger, Igor and Ritchie, Robert O. and Scholtes, Berthold}, title = {Isothermal Fatigue Behavior and Residual Stress States of Mechanically Surface Treated Ti-6Al-4V: Laser Shock Peening vs. Deep Rolling}, series = {Shot peening}, booktitle = {Shot peening}, editor = {Wagner, Lothar}, publisher = {Wiley-VCH}, address = {Weinheim; [Cambridge]}, isbn = {9783527606580}, doi = {10.1002/3527606580.ch57}, pages = {447 -- 453}, abstract = {In this paper, the high-temperature fatigue behavior and residual stress states of a Ti-6Al-4V alloy are investigated after mechanical surface treatment. In particular, the two surface treatments investigated, laser shock peening and deep rolling, were observed to result in significantly different residual stress states. The consequent isothermal fatigue behavior at elevated temperatures, characterized using cyclic deformation curves, are discussed in terms of the stability of the near-surface work hardening and compressive residual stresses. Despite pronounced relaxation of the residual stresses, both laser shock peening and deep rolling led to a significant improvement in the cyclic deformation behavior and, hence, increased fatigue lifetimes at elevated temperatures as compared to untreated materials states.}, language = {en} } @article{NosterScholtes, author = {Noster, Ulf and Scholtes, Berthold}, title = {Isothermal strain-controlled quasi-static and cyclic deformation behavior of magnesium wrought alloy AZ31}, series = {International Journal of Materials Research / Zeitschrift f{\"u}r Metallkunde}, volume = {94}, journal = {International Journal of Materials Research / Zeitschrift f{\"u}r Metallkunde}, number = {5}, doi = {10.1515/ijmr-2003-0098}, pages = {559 -- 563}, abstract = {The low-cycle and high-cycle fatigue behavior of the Mg-base wrought alloy AZ31 is investigated in the temperature range 20- 300 °C using total-strain-controlled push - pull tests. It is shown that the mechanical properties of the material are substantially influenced by the direction dependent formation of deformation twins and resulting deformation asymmetry. As a consequence tensile mean stresses develop during total-strain-controlled fatigue tests without mean strain.}, language = {en} } @article{BitscheNosterPeterlechner, author = {Bitsche, Robert and Noster, Ulf and Peterlechner, Christian}, title = {F{\"u}gepartner schl{\"u}ssig zu Leichtbaukomponenten verbinden?}, series = {Lightweight Design}, volume = {1}, journal = {Lightweight Design}, number = {2}, publisher = {Springer}, doi = {10.1007/BF03223528}, pages = {30 -- 34}, abstract = {Kombinationen aus kraft- und formschl{\"u}ssigen Verbindungen erh{\"o}hen die Leistung bei im Hybridguss verbundenen Gussteilen mit Anbau- oder Einlegeteilen und machen separate F{\"u}geprozesse {\"u}berfl{\"u}ssig. Simulations-Methoden unterst{\"u}tzen das Design kraft- und formschl{\"u}ssiger Verbindungen. Ergebnisse eines Ausdr{\"u}ckversuchs zeigen eine relativ gute {\"U}bereinstimmung zwischen gemessenen und mittels Simulation ermittelten Kraft-Weg-Kurven.}, language = {de} } @incollection{BillingerNoster, author = {Billinger, Wolfgang and Noster, Ulf}, title = {Bauteilfertigung}, series = {Leichtbau}, booktitle = {Leichtbau}, editor = {Degischer, Hans Peter}, publisher = {Wiley-VCH}, address = {Weinheim}, isbn = {9783527628247}, doi = {10.1002/9783527628247.ch4}, pages = {247 -- 278}, language = {de} } @inproceedings{KouakouoBoehmZimmermann, author = {Kouakouo, S. and B{\"o}hm, Valter and Zimmermann, Klaus}, title = {Analyses of apedal locomotion systems based on ferroelastomers}, series = {Proceedings I of the 28st Conference STUDENT EEICT 2022: General papers}, booktitle = {Proceedings I of the 28st Conference STUDENT EEICT 2022: General papers}, publisher = {Vysok{\´e} učen{\´i} technick{\´e} v Brně, Fakulta elektrotechniky a komunikačn{\´i}ch technologi{\´i}}, isbn = {978-80-214-6029-4}, pages = {447 -- 451}, abstract = {In this paper, the movement behavior of amoeboid locomotion system is investigated and the theoretical proof of the locomotion of the system is provided with the finite element method. It is shown that not only the speed of locomotion but also its direction can be influenced by the drive frequency. Depending on the drive frequency, a movement from the home position and a subsequent movement in opposite directions can be achieved. In addition, high speeds of movement can be achieved in a limited frequency range.}, language = {en} } @article{WalterSchwanzerHagenetal., author = {Walter, Stefanie and Schwanzer, Peter and Hagen, Gunter and Rabl, Hans-Peter and Dietrich, Markus and Moos, Ralf}, title = {Soot Monitoring of Gasoline Particulate Filters Using a Radio-Frequency-Based Sensor}, series = {Sensors}, volume = {23}, journal = {Sensors}, number = {18}, publisher = {MDPI}, issn = {1424-8220}, doi = {10.3390/s23187861}, pages = {1 -- 19}, abstract = {Owing to increasingly stringent emission limits, particulate filters have become mandatory for gasoline-engine vehicles. Monitoring their soot loading is necessary for error-free operation. The state-of-the-art differential pressure sensors suffer from inaccuracies due to small amounts of stored soot combined with exhaust gas conditions that lead to partial regeneration. As an alternative approach, radio-frequency-based (RF) sensors can accurately measure the soot loading, even under these conditions, by detecting soot through its dielectric properties. However, they face a different challenge as their sensitivity may depend on the engine operation conditions during soot formation. In this article, this influence is evaluated in more detail. Various soot samples were generated on an engine test bench. Their dielectric properties were measured using the microwave cavity perturbation (MCP) method and compared with the corresponding sensitivity of the RF sensor determined on a lab test bench. Both showed similar behavior. The values for the soot samples themselves, however, differed significantly from each other. A way to correct for this cross-sensitivity was found in the influence of exhaust gas humidity on the RF sensor, which can be correlated with the engine load. By evaluating this influence during significant humidity changes, such as fuel cuts, it could be used to correct the influence of the engineon the RF sensor.}, language = {en} } @inproceedings{SchaefferHerrmannBoehm, author = {Schaeffer, Leon and Herrmann, David and B{\"o}hm, Valter}, title = {Theoretical considerations on a 2D compliant tensegrity joint in context of a biomedical application}, series = {Engineering for a changing world : 60th ISC, Ilmenau Scientific Colloquium, Technische Universit{\"a}t Ilmenau, September 4-8, 2023}, booktitle = {Engineering for a changing world : 60th ISC, Ilmenau Scientific Colloquium, Technische Universit{\"a}t Ilmenau, September 4-8, 2023}, publisher = {Technische Universit{\"a}t Ilmenau}, address = {Ilmenau}, doi = {10.22032/dbt.58879}, pages = {1 -- 15}, abstract = {In this paper, a two-dimensional compliant tensegrity joint was investigated for potential biomedical applications such as orthotics or exoskeletons. The structure consists of two compressed members connected by five compliant tensioned members. The concept is based on the tensegrity principle, which allows the realization of dynamic orthoses without conventional hinge joints. Another advantage is the adaptability to the individual needs of the patient through a suitable design of the structure and the careful selection of the characteristics of the elements. Using geometric nonlinear analysis, the mechanical behavior of the structure was investigated, focusing on mechanical compliance. The main objective was to determine the influence of the initial length and stiffness of the tensioned members and the influence of the magnitude of external forces on the overall stiffness of the movable member of the structure. The results highlight the significant impact of member parameters on the structure's stiffness and movability under varying load magnitudes. The research laid the foundation for future development of dynamic orthoses based on this structure.}, language = {en} } @article{SchaefferHerrmannSchmausseretal., author = {Schaeffer, Leon and Herrmann, David and Schmausser, Theresa and Liebrecht, Melanie and Rambach, Felix and B{\"o}hm, Valter}, title = {Theoretische Untersuchungen zu einer neuartigen Handorthese : [Kurzfassung des Tagungsbeitrags]}, series = {10. IFToMM D-A-CH Konferenz 2024: 05./06. M{\"a}rz 2024, Universit{\"a}t Rostock.}, journal = {10. IFToMM D-A-CH Konferenz 2024: 05./06. M{\"a}rz 2024, Universit{\"a}t Rostock.}, doi = {10.17185/duepublico/81586}, language = {de} } @misc{Dendorfer, author = {Dendorfer, Sebastian}, title = {Sturz- und Frakturpr{\"a}vention: Use it or lose it!}, series = {10 Jahre Alterstraumatologie Caritas Krankenhaus St. Josef Regensburg}, journal = {10 Jahre Alterstraumatologie Caritas Krankenhaus St. Josef Regensburg}, language = {de} } @inproceedings{RiegervandeParRabletal., author = {Rieger, Anna and van de Par, Steven and Rabl, Hans-Peter and Oetjen, Arne}, title = {Ein Ton macht noch keine Harmonie - Der Einfluss von Tonhaltigkeit und Dissonanz auf Pr{\"a}ferenzurteile}, series = {Fortschritte der Akustik - DAGA 2023, 49. Jahrestagung f{\"u}r Akustik, 06.-09. M{\"a}rz 2023 in Hamburg}, booktitle = {Fortschritte der Akustik - DAGA 2023, 49. Jahrestagung f{\"u}r Akustik, 06.-09. M{\"a}rz 2023 in Hamburg}, publisher = {Deutsche Gesellschaft f{\"u}r Akustik e.V. (DAGA)}, address = {Berlin}, isbn = {978-3-939296-21-8}, pages = {1167 -- 1170}, abstract = {Produkt- bzw. Maschinenger{\"a}usche mit deutlich h{\"o}rbaren tonalen Komponenten werden h{\"a}ufig als l{\"a}stig empfunden. Wenn zus{\"a}tzlich eine Interaktion mehrerer tonaler Komponenten in Ger{\"a}uschen stattfindet, was in realen Szenarien beispielsweise durch die {\"U}berlagerung tonaler Komponenten durch verschiedene Aggregate, wie Motoren und Getrieben, stattfindet, dann k{\"o}nnen Ger{\"a}usche unterschiedlich tonal, aber auch unterschiedlich konsonant und dissonant wahrgenommen werden. Vorangehende H{\"o}rexperimente haben gezeigt, dass die Dissonanz bei {\"a}hnlicher Tonhaltigkeit der Ger{\"a}usche einen großen Einfluss auf die Pr{\"a}ferenzurteile hat. Des Weiteren konnte bereits ein grundlegendes Empfindungsmodell f{\"u}r die "Dissonanz" sowie ein Pr{\"a}ferenz-Pr{\"a}diktor entwickelt werden, die die Subjektivdaten in hoher G{\"u}te vorhersagen konnten. In den hier vorgestellten Versuchen wurde das Zusammenspiel zwischen der empfundenen Tonhaltigkeit und der sich aus mehreren Tonkomponenten ergebenden Dissonanz auf die Pr{\"a}ferenzurteile untersucht. In der Analyse wird aufgezeigt, auf welche Weise und in welchem Umfang die wahrgenommene Ausgepr{\"a}gtheit der Tonhaltigkeit durch Interaktion mehrerer Tonkomponenten die allgemeine Ger{\"a}uschqualit{\"a}t beeinflusst. Da verschiedene Grade der Dissonanz nur durch die gleichzeitige Anwesenheit tonaler Komponenten entstehen k{\"o}nnen, ist das Zusammenspiel beider Gr{\"o}ßen bei der Bildung eines Pr{\"a}ferenzurteils von einer speziellen Natur. Dies wird sowohl bei der Modellierung der Interaktion beider Gr{\"o}ßen als auch im Vorhersagemodell der Dissonanz ber{\"u}cksichtigt.}, language = {de} } @inproceedings{Fuhrmann, author = {Fuhrmann, Thomas}, title = {Semi-Structured Lab Projects in Communication Engineering Education}, series = {2023 IEEE Global Engineering Education Conference (EDUCON), 01-04 May 2023, Kuwait}, booktitle = {2023 IEEE Global Engineering Education Conference (EDUCON), 01-04 May 2023, Kuwait}, publisher = {IEEE}, doi = {10.1109/EDUCON54358.2023.10125244}, pages = {1 -- 5}, abstract = {It is generally known that project-based learning is a very important part of engineering education to connect theoretical knowledge with practical work. Students learn to apply their knowledge to real-world challenges as it is the case in their later professional life. If students are not used to project work or the scientific topic is new and relatively complex, they may be overwhelmed. The consequence is that students achieve poor results, are frustrated, and therefore learning success is low. Semi-structured projects are introduced that combine the advantages of structured experiments with projects. The project work is structured into several parts with detailed descriptions of the tasks. In the end, students get similar results to doing a free project, but the success rate is higher due to higher guidance. Therefore, these semi-structured projects are seen to be an appropriate method to guide students to learn how to do project work. The feedback from most students is very positive. Some students with no previous lab experience complained about the project work and wished for more guidance to become familiar with lab work. In sum, the student feedback is encouraging to develop semi-structured projects further.}, language = {en} } @article{NallaAltenbergerNosteretal., author = {Nalla, Ravi K. and Altenberger, Igor and Noster, Ulf and Liu, G.Y. and Scholtes, Berthold and Ritchie, Robert O.}, title = {On the influence of mechanical surface treatments—deep rolling and laser shock peening—on the fatigue behavior of Ti-6Al-4V at ambient and elevated temperatures}, series = {Materials Science and Engineering: A}, volume = {355}, journal = {Materials Science and Engineering: A}, number = {1-2}, publisher = {Elsevier}, issn = {1873-4936}, doi = {10.1016/S0921-5093(03)00069-8}, pages = {216 -- 230}, abstract = {It is well known that mechanical surface treatments, such as deep rolling, shot peening and laser shock peening, can significantly improve the fatigue behavior of highly-stressed metallic components. Deep rolling (DR) is particularly attractive since it is possible to generate, near the surface, deep compressive residual stresses and work hardened layers while retaining a relatively smooth surface finish. In the present investigation, the effect of DR on the low-cycle fatigue (LCF) and high-cycle fatigue (HCF) behavior of a Ti-6Al-4V alloy is examined, with particular emphasis on the thermal and mechanical stability of the residual stress states and the near-surface microstructures. Preliminary results on laser shock peened Ti-6Al-4V are also presented for comparison. Particular emphasis is devoted to the question of whether such surface treatments are effective for improving the fatigue properties at elevated temperatures up to ∼450 °C, i.e. at a homologous temperature of ∼0.4T/Tm (where Tm is the melting temperature). Based on cyclic deformation and stress/life (S/N) fatigue behavior, together with the X-ray diffraction and in situ transmission electron microscopy (TEM) observations of the microstructure, it was found that deep rolling can be quite effective in retarding the initiation and initial propagation of fatigue cracks in Ti-6Al-4V at such higher temperatures, despite the almost complete relaxation of the near-surface residual stresses. In the absence of such stresses, it is shown that the near-surface microstructures, which in Ti-6Al-4V consist of a layer of work hardened nanoscale grains, play a critical role in the enhancement of fatigue life by mechanical surface treatment.}, language = {en} } @article{NosterScholtes, author = {Noster, Ulf and Scholtes, Berthold}, title = {Bauschingerefekt und mechanische Zwillingsbildung der Magnesiumlegierung AZ31}, series = {H{\"a}rterei-technische Mitteilungen : HTM ; Zeitschrift f{\"u}r Werkstoffe, W{\"a}rmebehandlung, Fertigung}, volume = {58}, journal = {H{\"a}rterei-technische Mitteilungen : HTM ; Zeitschrift f{\"u}r Werkstoffe, W{\"a}rmebehandlung, Fertigung}, publisher = {Hanser}, pages = {322 -- 327}, language = {de} }