An alternative procedure to identify stress-strain relation for DP980 sheet over a large strain range

Abstract

In sheet metal forming, the standard uniaxial tensile test is a well-established testing method used to achieve stress-strain relation or flow curve for examined material. In agreement with the development of material science, the number of forming processes that exceeded the maximum uniform strain observed in a uniaxial tensile test is myriad. To obtain the relationship between stresses and strains over a large range of deformation, extrapolation of a common hardening model (Swift model or Voce model) is only accepted for some specific materials. Therefore, expensive calibrating methods, such as inverse finite element analysis and virtual field method, are widely used to identify the flow curve for recently developed sheet materials, for example, advanced high strength steels or aluminium alloys. This study presents an alternative procedure to identify the flow curve for sheet metals by using the extrapolation method. Key to the success of this procedure is using the Kim-Tuan hardening model, a newly developed hardening model proposed by the authors. The examined material is DP980 sheet that is tested material in Benchmark 01 of the NUMISHEET 2018 conference. To verify the accuracy of the calibrated flow curve, this curve is imported into a finite element analysis for a uniaxial tensile specimen and computational loading forces according to gauge length displacement are compared with experimental observation supported from the Benchmark's data.