Experimental and numerical studies of Edge Rounding Process in HSLA steels sheet metal

摘要

Blanking of sheet-metal is an important forming process in the automotive industry for the manufacture of mechanical components. The final component shape, obtained at the end of bending or deep-drawing processes, often has sharp edges due to the blanking operation. Concerning passenger safety components, like seat belt anchors, rounding of the edges by punching is necessary to avoid cutting the belt material. In addition to removing the sharp edges, the punching results in work hardening of the material in the rounded zones which results in an increase in the local resistance of the material. In this study, a High Strength Low Alloy steel (HSLA S500MC) has been tested with the aim of qualifying the blanking and edge rounding operations. The mechanical behavior of test specimens is investigated by means of tensile tests and the material is characterized in terms of Vickers micro-hardness. Numerical simulations of the edge rounding process are developed using previously identified material behavior laws. The residual stress fields are characterized and compared to experimental results, in view of future numerical simulation to prediction the in-service behavior of the component. Specimens with rounded edges are compared to specimens that were not submitted to the rounding operation. It is shown that Edge Rounding by Punching (E.R.P.) improves the component resistance, therefore justifying the use of this process in the manufacture of automotive safety components.