Numerical studies of low cycle fatigue in forward extrusion dies

Forward extrusion dies typically fail due to transverse fatigue cracks or w ear. Fatigue cracks are initiated in regions where the material is subjecte d 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 st udy the effects of different pre-stressing concepts on the accumulation of plastic strain and the development of fatigue damage. The results show, tha t the accumulation of plastic strain in the critical region can be controll ed by means of the pre-stressing system or the geometry of the die insert. (C) 2000 Elsevier Science B.V. All rights reserved.