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Publisher: Cambridge : Cambridge University Press × WGL Institute: INM ×

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Now showing 1 - 4 of 4
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    Adhesion behavior of polymer networks with tailored mechanical properties using spherical and flat contacts
    (Cambridge : Cambridge University Press, 2013) Lakhera, Nishant; Graucob, Annalena; Schneider, Andreas S.; Kroner, Elmar; Micciché, Maurizio; Arzt, Eduard; Frick, Carl P.
    Four acrylate-based networks were developed such that they possessed similar glass transition temperature (~-37 °C) but varied in material stiffness at room temperature by an order of magnitude (2-12 MPa). Thermo-mechanical and adhesion testing were performed to investigate the effect of elastic modulus on adhesion profiles of the developed samples. Adhesion experiments with a spherical probe revealed no dependency of the pull-off force on material modulus as predicted by the Johnson, Kendall, and Roberts theory. Results obtained using a flat probe showed that the pull-off force increases linearly with an increase in the material modulus, which matches very well with Kendall's theory.
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    Indentation-induced two-way shape-memory effect in aged Ti-50.9 at.% Ni
    (Cambridge : Cambridge University Press, 2015) Frensemeier, Mareike; Arzt, Eduard; Qin, Enwei; Frick, Carl P.; Schneider, Andreas S.
    In this study, Vickers indentation was used to investigate the two-way shape-memory effect (TWSME) in an austenitic Ti-50.9 at.% Ni alloy, exposed to different heat treatments. Three aging treatments were used to manipulate the size of Ti3Ni4 precipitates. All samples were Vickers indented, and the indent depth was investigated as function of thermal cycling. The TWSME was found only in the material aged at 400 Â°C, which contained coherent precipitates. Thermal cycling shows stable TWSME, however, heating well above the austenite finish temperature lead to permanent austenitic protrusions. The results indicate that stabilized martensite plays a critical role in creating TWSME surfaces.
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    In situ observation of contact mechanisms in bioinspired adhesives at high magnification
    (Cambridge : Cambridge University Press, 2011) Paretkar, Dadhichi; Schneider, Andreas S.; Kroner, Elmar; Arzt, Eduard
    We analyzed the contact mechanisms of bioinspired microfibrillar adhesives using in situ scanning electron microscopy. During adhesion tests we observed that (i) the superior adhesion of mushroom-shaped fibrils is assisted by the stochastic nature of detachment, (ii) the aspect ratio of microfibrils influences the bending/buckling behavior and the contact reformation, and (iii) the backing layer deformation causes the microfibrils to elastically interact with each other. These studies give new insights into the mechanisms responsible for adhesion of bioinspired fibrillar adhesives.
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    High strength nanocrystalline Cu–Co alloys with high tensile ductility
    (Cambridge : Cambridge University Press, 2018) Bachmaier, Andrea; Rathmayr, Georg Benedikt; Schmauch, Jörg; Schell, Norbert; Stark, Andreas; de Jonge, Niels; Pippan, Reinhard
    A supersaturated single-phase Cu–26 at.% Co alloy was produced by high-pressure torsion deformation, leading to a nanocrystalline microstructure with a grain size smaller than 100 nm. The nonequilibrium solid solution decomposed during subsequent isothermal annealing. In situ high-energy X-ray diffraction was used to map changes linked to the separating phases, and the development of a nanoscale Cu–Co composite structure was observed. To gain further information about the relationship of the microstructure and the mechanical properties after phase separation, uniaxial tensile tests were conducted on as-deformed and isothermally annealed samples. Based on the in situ diffraction data, different isothermal annealing temperatures were chosen. Miniaturized tensile specimens with a round cross section were tested, and an image-based data evaluation method enabled the evaluation of true stress–strain curves and strain hardening behavior. The main results are as follows: all microstructural states showed high strength and ductility, which was achieved by a combination of strain-hardening and strain-rate hardening.