Extension of the normalized Cockcroft and Latham criterion with temperature-dependent critical damage values for predicting chevron cracks in solid forward extrusion

Abstract

The fracture criterion according to Cockcroft and Latham in combination with the element deletion method is suitable for a numerical prediction of chevron cracks in solid forward extrusion. Conventionally, the element deletion method uses a constant critical damage value. The exceedance of this value leads to the deletion of elements from the mesh. The use of constant critical damage values leads to an inaccurate prediction of crack location and form when forming takes place at different process temperatures. Therefore, this work proposes the use of a temperature-dependent critical damage value. Implemented in Deform 2D through user subroutines and verified by experiments it is shown that the proposed methodology improves the numerical prediction of chevron crack formation for process temperatures ranging from cold to warm forming.