Light press of sheet metal edge for reducing residual stress generated by laser cutting considering mechanical properties and intensity of residual stress

Abstract

Laser cutting has started to be used as an effective method for cutting out blanks from rolled sheet metals because of its high flexibility for cutting lines and high productivity. However, residual stresses, which are generated by laser cutting, have been the greatest obstacle for the popularization of laser cutting. One of the problems is the warp which appears in the sheet metal after being subjected to bending processes after laser cutting. The authors present a light press method for reducing residual stress generated by laser cutting. The method is to give a light press on the sheet metal edge and to reduce tensile residual stress generated near the laser cutting surface. In particular, this present paper especially focuses upon optimization of working conditions depending on mechanical properties of the blank and the effect of the heat affected zone in laser cutting. Experiments of U-bending after applying light press were conducted for usability of this method. The FEM analyses were carried out in order to investigate proper working conditions depending on various mechanical properties. As a result, the optimum press pressure of the light press method for various mechanical properties was found out for reducing residual stress which caused by laser cutting, by taking warp after U-bending as an evaluation parameter. The relationship between the optimum pressure and the proof stress was quantitatively and specifically clarified for several sets of mechanical properties. It was also found that the influence of heat-affected-zone area and intensity of residual stress by laser cutting on the optimum press pressure was small.