The determination of material strength coefficient and strain hardening constant by inverse method

In the process of metal plastic forming, the flow stress formula has always been a significant basis for analyzing plastic deformation. The material strength coefficient and strain hardening constant are the two major and indispensable parameters of the stress flow formula. According to the ASTM specifications, the traditional way of finding the material strength coefficient and strain hardening constant has to go through a lot of complicated and long calculations. This paper develops an inverse calculation process of the material strength coefficient and strain hardening constant based on the experimental upsetting load. The calculating process of the material strength coefficient and strain hardening constant can be simplified. Taking the values of experimental upsetting load as a basis, this paper adopts the numerically optimized Levenberg–Marquardt method, together with a proper objective function and convergence criterion along with the elastic–plastic finite element method, for inverse calculation of the strength coefficient and strain hardening constant. The comparison between the measured profiles of the material in experiment and the simulated profiles with the inverse calculation shows an excellent match. It also shows that the results of the inverse method developed in this paper exhibit more accurate values of the material strength coefficient and strain hardening constant, these values can be acquired more quickly for comparison with the traditional method.