Damage field ahead of a tensile crack in an elastic-plastic and viscoplastic material

This paper investigates the interaction between a macroscopic crack and mic roscopic damage in an elastic-plastic and viscoplastic material subjected t o tensile in-plane loading. The aim is to predict the fracture conditions b y accounting for void accumulation in the vicinity of the crack-tip. A powe r law relates the stress to the strain of the material. The damage, which i nvokes the growth and coalescence of microvoids, is confined to a small cir cular zone surrounding the crack-tip. At the onset of crack extension, the applied stress for small-scale and large-scale yielding solutions is found to be proportional to a(0)(-1/(n+1)), where 2a(0)is the initial crack lengt h and n is the strain hardening exponent of the material. For small-scale y ielding, the conditions required for fatigue crack growth and steady-state creep are determined. In particular, the variations of the normalized crack length with the number of loading cycles and the time required for failure are shown for various strain hardening exponents, applied loading, and mat erial damage parameters.