Modeling dynamic fracture processes in brittle materials

Sahir Butt, Ruhr Universität Bochum, Bochum, Germany
Günther Meschke, Ruhr University Bochum, Bochum, Germany

In this study, we investigate the dynamic fracture process in amorphous brittle materials using 3D peridynamic analyses of dynamic crack propagation in PMMA plates subjected to quasi-static loads. This loading condition allows one to assume, that the crack will accelerate to a steady-state velocity and will continue propagating at a constant velocity. Dynamic crack instability and its effect on the fracture surface creation as well as the dissipated energy is analyzed numerically for cracks propagating at different velocities. Simulations reproduce many salient features of experimental observations, such as instabilities of crack occurring for cracks propagating above a certain critical velocity. It is shown from the simulations, that increasing crack velocity results in excessively repeated microbranching and a higher energy dissipation. Delta- and n-convergence, i.e. the effect of the peridynamic horizon and the mesh size on the fracture process, is investigated for cracks propagating at different speeds. From delta-convergence study one can conclude, that the elastic wave dispersion properties have a significant effect on the velocity of the macro-crack and subsequent velocity dependent dissipation mechanisms. Real world specimens have microstructural defects and spatial fluctuations in the material strength. We investigate these effects using a Weibull distribution of bond strengths in the peridynamic simulations. Simulations performed earlier with homogenous strength are now carried out using statistically distributed strengths. The effects of the statistically distributed strength on the crack instability and crack propagation velocity are investigated.

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