An efficient method to estimate the post-necking behavior of sheet metals

摘要

In sheet metal-forming studies, the flow curve reproduced by a hardening function is commonly determined using experimentally measured stress-strain data obtained from a uniaxial tensile test. There are numerous forming processes that require the tested materials to undergo a deformation exceeding the maximum strain observed in the tensile test. Numerical analyses for such forming processes involve a reasonable estimation of the stress-strain relationship at large strains or post-necking prediction. Extrapolating the calibrated hardening function to large strains is the most common method to achieve this goal. However, application of this method is limited for certain specific materials. Hence, expensive calibrating methods such as inverse finite element methods and virtual field methods are frequently used to identify the flow curve for lightweight sheet metals. This study presents an efficient method to estimate the post-necking behavior of sheet metals. The key to the success of the method is the use of a newly developed hardening model. The method is applied to calibrated flow curves for three lightweight sheet metals: DP980, AL5052-O, and commercially pure titanium sheets to verify its potentiality. The calibrated flow curves are then imported into the ABAQUS/EXPLICIT software package to simulate uniaxial tensile tests and bulge tests for the examined materials. Matching between the experimentally measured data and simulation results of tensile force (for tensile specimens) and pole height (for bulge specimens) validates the accuracy of the calibrated flow curves obtained from the presented method, especially in post-necking ranges.