Nonlinear response to probe vitrification

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P1 Konrad Samwer, Universität Göttingen

Nonlinear effects induced by mechanical stresses in glass-forming systems far from equilibrium

This project is dedicated to nonlinear effects in the strain response of bulk metallic glasses
under applied tensile mechanical stresses. It focusses on (i) the strain response to a periodic
excitation under additionally applied strong mechanical load, exhibiting higher harmonics as a
consequence of nonlinear effects. Further, the time dependent lengthening under constantly
applied tensile stress is studied. It shows creep-like characteristics which indicate an anelasticto-
plastic phase transition in dependence of stress and temperature (ii). Finally, the analysis
of such creep curves–and, in particular, their statistical properties–gives important insights into
the of avalanche-like nature of the rearrangement events (iii). The macroscopic experimental
approach is mainly based on different modes of the dynamical mechanical analysis (DMA)
method. Furthermore, we will make a step forward from global to local measurements in the
upcoming funding period, too. Therefore we will perform complex force microscopy eperiments
under periodic excitation (atomic force acoustic microscopy, AFAM) and nanoindentation measurements
using a diamond tip in an AFM for intermittent effects in the so-called elastic regime.