Analysis of loads on the shearing edge during electrohydraulic trimming of AHSS steel in comparison with conventional trimming

Abstract

In order to achieve further weight reduction in automotive components, the technology of manufacturing of automotive panels from advanced high strength steels is being developed. Electrohydraulic trimming technology eliminates the necessity of accurate alignment of the shearing edges in trimming operation. Analysis of loads on the tool during high-rate EH trimming process has been performed. In order to investigate the effect of the process on the shearing edge performance, a dedicated finite element analysis procedure combining 3D shell and 2D solid models was developed. EH trimming experiments were carried out to validate the simulation model where elastic plastic deformation of the shearing edge was taken into account. The effects of the die geometry and number of trimming cycles on the tool contact loads and tool's plastic deformation were analyzed. This analysis was based on numerical simulation of deformation and fracture of the blank being trimmed in contact with the deformable shearing edge. Numerical analysis of the shearing edge deformation was performed in elasto-plastic formulation for the D2 tool steel inserts used in the experimental study and also in elastic formulation to define the maximum stresses which tool material needs to withstand to avoid its plastic deformation.The results of the analytical study indicate that the maximum contact pressure is applied to the trimming tool at the lower endpoint of the shearing edge, but the point of maximum plastic deformation in the tool is found on the vertical wall of the shearing edge where it contacts the area of the blank where separation takes place. The shearing edge of the EH trimming die experiences less contact pressure and less plastic deformation with increase of the radius of the shearing edge. The shearing edge of the EH trim die has a tendency to dull after a number of trimming cycles. In addition, when compared with conventional trim die, the shearing edge of the EH trimming tool experiences slightly higher (10–15%) contact loads than in conventional trimming. However, plastic deformations occurring in the conventional trim die for shearing of identical material are larger. Analysis of loads on the EH trimming tool was repeated for purely elastic tool material to formulate the requirements to the material of the shearing edge.