Effect of shear cutting induced strain on edge crack sensitivity of workpiece

Failure prediction in sheet metal forming simulation still shows some severe gaps especially in context to high strength steels and other light weight material manufacturing. Prediction of edge cracks of sheet metals due to forming operations resulting from shear cutting of the sheets is one example for such limitations in failure detection. Literature shows a direct link between shear cutting process and reduced formability due to edge cracking. The aim of this study was to find a correlation between strain induced along workpiece outline due to cutting process and corresponding development of edge crack sensitivity of component edge. A strain measurement system was used to acquire the strain in sheet thickness direction on the one hand and the maximum strain value emerging before necking by conducting newly developed Diabolo Test on the other hand. The Diabolo Test is a novel test setup for gauging the edge crack sensitivity along trimmed parts edges and was developed as an alternative to the Hole Expanding test according to ISO 16630. To quantify effects of changings in strain distribution in sheet thickness direction on edge crack sensitivity strain measurements with different sheet thicknesses and cutting clearances were conducted. By generating a deeper comprehension of mechanisms of edge cracking, the obtained data could be used to get one step further in modeling edge crack sensitivity in sheet metal simulation.