Numerical studies of low cycle fatigue in forward extrusion dies

Forward extrusion dies typically fail due to transverse fatigue cracks or wear. Fatigue cracks are initiated in regions where the material is subjected to repeated plastic deformations, e.g. the transition radius in a forward extrusion die. In the present work, a material model capable of describing the elastic–plastic material behaviour under cyclic loadings is used to study the effects of different pre-stressing concepts on the accumulation of plastic strain and the development of fatigue damage. The results show, that the accumulation of plastic strain in the critical region can be controlled by means of the pre-stressing system or the geometry of the die insert.