Crack surface contact under alternating plasticity

摘要

The opening and closing of a crack subjected to alternating plasticity is analysed, with a view to characterising the closure behaviour of short fatigue cracks under cyclic plasticity. Elastic-plastic finite element analysis has been conducted where a non-linear kinematic hardening constitutive law is used to model the material's cyclic plasticity. Both crack-centre opening displacement and crack-tip opening displacement have been determined under fully reversed cyclic loading, with the maximum applied strain being up to ten times the material's yield strain. Under cyclic loading conditions, the crack opening displacement at the maximum stress has been found to increase with the number of cycles, approaching an asymptotic limit that is more than twice that corresponding to the first half cycle. An analytical model has been developed to characterise this transient ratchetting in the crack opening displacement.