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Author: Müser, Martin H. × End date: 2022 × Start date: 2020 × DDC: 530 × WGL Institute: INM ×

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    On the viscous dissipation caused by randomly rough indenters in smooth sliding motion
    (Amsterdam : Elsevier, 2021) Sukhomlinov, Sergey; Müser, Martin H.
    The viscous dissipation between rigid, randomly rough indenters and linearly elastic counter bodies sliding past them is investigated using Green’s function molecular dynamics. The study encompasses a variety of models differing in the height spectra properties of the rigid indenter, in the viscoelasticity of the elastomer, and in their interaction. All systems reveal the expected damping linear in sliding velocity at small and a pronounced maximum at intermediate . Persson’s theory of rubber friction, which is adopted to the studied model systems, reflects all observed trends. However, close quantitative agreement is only found up to intermediate sliding velocities. Relative errors in the friction force become significant once the contact area is substantially reduced by sliding.
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    Analytical and numerical results for the elasticity and adhesion of elastic films with arbitrary Poisson’s ratio and confinement
    (London [u.a.] : Taylor & Francis, 2022) Müller, Christian; Müser, Martin H.
    We present an approximate, analytical treatment for the linearly elastic response of a film with arbitrary Poisson's ratio (Formula presented.), which is indented by a flat cylindrical punch while resting on a rigid foundation. Our approach is based on a simple scaling argument allowing the vast changes of the elastomer’s effective modulus (Formula presented.) with the ratio of film height (Formula presented.) and indenter radius (Formula presented.) to be described with a compact, analytical expression. This yields exact asymptotics for large and small reduced film heights (Formula presented.), whereby it also reproduces the observation that (Formula presented.) has a pronounced minimum for (Formula presented.) at (Formula presented.). Using Green’s function molecular dynamics (GFMD), we demonstrate that the predictions for (Formula presented.) are reasonably correct and generate accurate reference data for effective modulus and pull-off force. GFMD also reveals that the nature of surface instabilities occurring during stable crack growth as well as the crack initiation itself depend sensitively on the way how continuum mechanics is terminated at small scales, that is, on parameters beyond the two dimensionless numbers (Formula presented.) and (Formula presented.) defining the continuum problem.