Advanced Characterization of Sheet Metal Deformation and Forming Using Digital Image Correlation

摘要

Advanced testing methods are required in order to accurately characterize the deformation and failure behaviour of anisotropic sheet metals. Full-field strain mapping techniques using digital image correlation (DIC) offer improved spatial and temporal measurement of material deformation, which allows yield and forming limit criteria to be assessed with greater fidelity. In the current work, full-field strain mapping was applied to characterize the biaxial flow response of anisotropic sheet metal. Full-field strain measurements, combined with analytical methods, allowed for the flow response to be measured for pure biaxial stress paths. It was found that the DIC strain data could be used to accurately predict the biaxial hardening response of sheet materials to high levels of effective strain, much higher than the uniform strain obtained from a tensile test. To adequately describe the hardening response of the material at these high levels of strain it was necessary to account for the anisotropy of the sheet. Full-field strain mapping techniques were also used to study forming response of anisotropic sheet metal. Advantages of DIC included the capability to determine the forming response at strain-rates approaching those in stamping operations and the ability to vary the gauge length in the strain measurement for analysis after the test was performed.