A Comparison of Fracture Limit Analysis on Titanium Grade 2 and Titanium Grade 4 Sheets During Single Point Incremental Forming

The influence of tensile properties, void coalescence parameters, strain triaxiality (epsilon(m)/epsilon(eff)) and its fracture limits for various spindle rotational speeds in single point incremental forming were compared for titanium grade 2 and grade 4 sheets. The microstructure reveals the presence of alpha and beta phase particles, as was confirmed using x-ray diffraction analysis. Forming limit diagrams and fracture limit curves were plotted for the sheets and the results were compared for both titanium grade sheets. The void coalescence in fractured samples showed an improved fracture resistance for the titanium grade 2 sheets compared with the titanium grade 4 sheets. The void size, ligament thickness, void (L/W) ratio, d-factor, strain triaxiality and further void coalescence parameters were also compared. In all cases, because of their better ductility, the titanium grade 2 sheets exhibited better forming and fracture limits (void coalescence) than that of grade 4 sheets.