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Published on: January 16, 2019
Crack Propagation by Activated Avalanches during Creep and Fatigue from Elastic Interface Theory
Tero Mäkinen1, Lumi Tuokkola1, Joonas Lahikainen1
1Aalto University, Department of Applied Physics, P.O. Box 15600, 00076 Aalto, Espoo, Finland.
Abstract:
The growth of cracks combines materials science, fracture mechanics, and statistical physics. The importance of fluctuations in the crack velocity is fundamental since it signals that the crack overcomes local barriers such as tough spots by avalanches. In ductile materials the omnipresent plasticity close to the crack tip influences the growth by history effects, which we here study in polymethylmetacrylate by various fatigue and creep protocols. We show how the crack tip local history may be encompassed in a time- and protocol-dependent length scale, which allows us to apply a statistical fracture description to the time-dependent crack growth rate, resolving the well-known paradox why fatigue cracks grow faster if the stress during a cycle is let to relax more from the peak value. The results open up novel directions for understanding fracture by statistical physics.
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