Numerical investigation of crack tip fields in viscoplastic materials

Abstract

The crack tip fields in viscoplastic materials are analysed by the finite element method. The mesh refinement required for an accurate description is determined from a comparison of the FE-results with analytical near-tip solutions which are available for two special models [1]. For the determination of the crack tip parameter C(t) or the creep zones a much coarser mesh is, however, adequate. Moreover, typical properties that reflect the geometry and loading are calculated for a number of specimens. It is demonstrated that C(t) can be approximated by an interpolation formula and that it is independent of the mathematical form of the constitutive equations if the material parameters are determined from the same set of uniaxial creep curves. The way in which C(t) depends on the load is, in general, not known whereas for the Norton law scaling relations are available.