Size effects at a crack-tip interacting with a number of voids

Abstract

A strain gradient plasticity theory is used to analyse the growth of discretely represented voids in front of a blunting crack tip, in order to study the influence of size effects on two competing mechanisms of crack growth. For a very small void volume fraction the crack tip tends to interact with one void at a time, whereas larger void volume fractions lead to simultaneous interaction of multiple voids on the plane ahead of the crack tip. The present computations are stopped before coalescence of the nearest void with the crack tip. Analyses are carried out for different values of the characteristic material length relative to the initial void radius. For a case showing the multiple void mechanism, it is found that the effect of the material length can change the behaviour towards the void by void mechanism. A material model with three characteristic length scales is compared with a one length scale model and the differences are discussed.

Keywords:

• plasticity
• finite strains
• ductile fracture
• crack growth
• voids