Hybrid fitting-numerical method for determining strain-hardening behavior of sheet metals

The uniaxial tensile test is well-established for experimentally identifying the stress-strain relationship for sheet metals. Conventionally, true stress-strain data obtained from the test are used to identify the hardening law's parameters using the curve-fitting method. Extrapolation using the identified hardening law describes the stress-strain relationship at large strains; however, it varies widely, depending on the selection of hardening models and their identified parameters. This study presents a hybrid method incorporating the curve-fitting method and inverse finite element analysis to identify the Kim-Tuan hardening model's parameters over large strain ranges. Here, the curve-fitting method enforces the identified hardening law's accuracy in the pre-necking range. Simultaneously, the inverse finite element analysis method maintains the goodness of the post-necking prediction. The proposed method is used to calibrate hardening laws for DP780 and AA6016-T651 sheet metals subjected to uniaxial tensile tests at room and warm temperatures, respectively. The calibrated hardening laws capture the force-displacement curves of both materials well, validating the ability of the presented method in practice.

Automated summary

This study proposes a hybrid method combining curve-fitting and inverse finite element analysis to identify the parameters of the Kim-Tuan hardening model over large strain ranges. By calibrating the hardening laws, the stress-strain relationship of sheet metals can be effectively captured.