Work Hardening of Metallic Sheets under Tension-Compression and Simple Shear Reverse Loading

Abstract

The hardening models have a significant influence on the accuracy of finite element analysis (FEA). Although, isotropic hardening models are the most widely used, it is known that kinematic hardening models (describing the Bauschinger effect and permanent softening) can significantly improve the accuracy of FEA results. However, when considering sheet metal materials, the parameters of kinematic hardening models are difficult to identify due to the challenges of obtaining experimental results from test with strain path inversions. This work considers an experimental procedure that enables the analysis of the mechanical behaviour of sheet metal materials submitted to reverse loadings. A miniaturized test device was developed to perform tension and compression tests, with reverse loadings, for sheet metal materials. This specimen design has two main advantages: (1) reduces buckling during compression (compared to standard tensile test specimens) and, consequently, (2) enables the characterization of the mechanical behaviour under reverse tension-compression strain paths changes. The small size of the specimens, with 2 x 2 mm gauge area, poses the main challenge of the current methodology, namely the measurement of the strain field distribution using the Digital Image Correlation (DIC) technique. The results obtained from tension-compression tests with mini-specimens are validated by comparison with standard tensile and shear (reverse loading) and tests.