Approximate Analysis on Strain Rate Effects and Behavior of Stress and Strain Fields at the Crack Tip in Mode II in Metallic Materials. Appendix Number 1.

摘要

Analysis of conditions for crack initiation and fracture toughness in the case of metallic materials under various loading rates are problems of great interest in fracture mechanics. Several investigations have been carried out to reveal the loading rate effect on fracture toughness. At the same time, systematic analyses have been performed for a majority of structural materials to study strain rate effect on the yield stress, ultimate stress, material strain hardening, etc. Some correlations between fracture toughness and parameters of stress-strain diagram at different strain rates have been derived. The theoretical background of such correlations consists of solutions for elastic and elastic-plastic stress-strain fields near a crack tip. Analyses of stress distribution at the tip of a stationary crack under dynamic loading have been performed by Freund (1990) and Lee and Freund (1990). Another important application of fracture mechanics arises from a relationship between loading rate and specimen thickness for fracture toughness measurements.