A method for direct measurement of multiaxial stress-strain curves in sheet metal

A method has been developed that allows measurement of stress-strain curves for sheet metal being deformed in multiaxial tension. The strain state is imposed using a modification of the Marciniak in-plane biaxial stretching test. Resulting stresses are measured using a modified X-ray diffraction (XRD) residual stress measurement system. This system is flexible enough to allow spatial mapping of in-plane stress and measurement of stresses at specific locations of interest on the sample, such as developing localizations. Results are presented correlating measurements on a thin strip of AA5182 with data from standard uniaxial tension test. Also presented are experimentally determined curves for this material in balanced biaxial tension in both the rolling and transverse directions. [PUBLICATION ABSTRACT]