Advances in the application of non-local damage models in the simulation of ductile crack-extension
(2004)
Local damage models usually have the disadvantage that results are strongly mesh dependent. The reason is that the type of the underlying partial differential equations changes under quasi-static conditions from elliptic to hyperbolic. Non-local damage models do not exhibit such behaviour under certain conditions. The usage of such non-local damage models in finite element analyses opens the possibility for preserving the ellipticity of the partial differential equations and thus avoiding mesh dependence of numerically obtained results. The loss of ellipticity for local models and its preservation for non-local models are demonstrated for a wide variety of examples enclosing ductile damage. In the present investigation, the non-local damage model is applied to the simulation of ductile crack extension in fracture mechanics specimens. The type of the underlying differential equations is permanently analysed and controlled.
Purpose is the formulation, numerical implementation, identification and application of a material model for ductile damage and failure during cyclic and non-proportional loading.
The authors combined a hyperelasticity-based elasto-plastic model for non-linear isotropic as well as kinematic hardening with a modified Gurson model. Evolution strategy helped identify the model parameters for the high-strength steel 10MnMoNi5-5. The simulation of ductile failure in fracture mechanics specimens verified the model with respect to cyclic loading at two temperatures. The simulation of additional fracture mechanics applications validated the model as to the development of residual stresses at the crack tip under cyclic loads.