definition a new dimensionless parameter on geometric ones affecting the chevron crack formation in an extrusion process

The central burst defect, also called chevron crack, in the extruded products is analysed by using 2D finite element analysis (FEA) to investigate the effects of affecting parameters on its formation, the three main ones are: cone angle, reduction and friction. By simulating an extrusion process in ABAQUS and changing these variables, some of the results like Von Mises stress, hydrostatic stress and strain in the longitudinal direction are discussed. Due to these results, some curves have been developed to show the safe and dangerous zone to the formation of chevron cracks. The results are also compared with some available experimental data. Also, for reducing the number of variables, a new dimensionless parameter is defined which combine two geometric ones, cone angle and reduction in area. It is suggested that this parameter can satisfy the effects of both of them; it means that as it is increased, whether due to the increasing in the cone angle or decreasing in the reduction in area percentile, the probability of chevron crack formation will be increased.

Keywords:

Chevron crack , Dimensionless parameter , Extrusion , Reduction