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Prediction of springback has become a major focus in sheet metal forming. Validation of finite element codes that are being developed to predict springback require accurate property data and a more complete understanding of the residual stresses that are involved. To provide experimental data for these calculations, neutron and synchrotron X-ray diffraction measurements were carried out to determine the through-thickness distribution of axial and hoop (or tangential) residual stresses in deep-drawn steel and aluminum cups. The techniques are able to provide true spatial resolutions as low as 0.05 mm for a strain measurement on cups with ≤ 1 mm wall thickness. It was found that the stresses exhibit non-linear gradients through the thickness that also depend on the axial position.

Experimental procedures and results of a benchmark test for springback are reported and a complete suite of obtained data is provided for the validation of forming and springback simulation software. The test is usually referred as the Slit-Ring test where a cylindrical cup is first formed by deep drawing and then a ring is cut from the mid-section of the cup. The opening of the ring upon slitting releases the residual stresses in the formed cup and provides a valuable set of easy-to-measure, easy-to-characterize springback data. The test represents a realistic deep draw stamping operation with stretching and bending deformation, and is highly repeatable in a laboratory environment. In this study, six different automotive materials are evaluated.