Simulation of crack resistance using a cohesive model: large scale yielding conditions

Fracture resistance curves (R curves) for describing ductile material behav iour play an important rule for integrity assessment analyses. The determin ation of R curves is widely expressed by experimentally based standardized procedures. But the considered standard test specimens are usually small si zed and the problem of resistance transferability from small laboratory spe cimens under large scale yielding to large sized structures under contained yielding emerges. It will be presented in the following a new strategy bas ed on a cohesive type model in combination with the conventionally finite e lement method. It allows numerical simulations of stable (ductile) tearing uniquely for small scale yielding (presented formerly in this journal) as w ell up to fully plastic deformation states only by two constant material pa rameters, With the respective choise of cohesive parameters it is possible to generate synthetical resistance curves which allows a new systematic und erstanding of the driving influences and their margins, especially the geom etry (loading) induced variations. By changing the two cohesive parameters an arbitrary material can be introduced where the correlation between mater ial and resistance behaviour can be answered. Furthermore, the inhomogeneou s behaviour of compounds, made of different material phases, can be investi gated straightforward and opens new perspectives in the fields of engineeri ng testing and characterization. Conventional methods as used for homogeneo us cases are no more sufficient for many aspects of new composed materials and structures.