Influence of Longitudinal Scratch Defects on the Bendability of Titanium Alloy

Abstract

Post-manufacturing induced defects in the form of scratches are sometimes inadvertently introduced onto sheet metal surfaces during either transportation, storage or handling. However, limited research has been previously carried out to establish the impact of such surface defects on sheet formability. Test trial results after press brake forming of Ti-3Al-2.5V showed that for longitudinal scratches oriented along the sheet rolling direction, scratch profiles with depth in the ranges of -1μm to -18μm and pile up height between 1μm to 16μm can be successfully formed; hence could be deemed acceptable during the sheet selection process. Failure of the coupons during the press brake forming trials was due to the impact of the scratch defects in their role as stress raisers and occurred primarily at the longitudinal scratch defect zones