Damage mechanics for the fracture prediction of metal forming tools

In this paper, a damage mechanics approach is shown to be useful for the prediction of fatigue fracture in metal forming tools. The approach can be applied in the general situation of under complex loading at elevated temperature. A damage criterion used considers initiation and propagation of cracks and fracture to be the accumulation of damage up to certain critical levels. This criterion is based on ductile properties of material. These properties are determined by the dependence of critical local strain on stresses and temperature and by the dependence of intensity of damage accumulation on the same parameters. The testing equipment and test methods are described. The results of an investigation of H13 hot work steel are included. The capability of the method is demonstrated by the prediction of crack initiation in a `disc-on-disc' experiment. This paper presents clear description of fatigue damage based on experiments.