Study of Formability Limit Based on Ductile Damage Criteria of Incremental Sheet Forming of Titanium Grade 2 Sheet

Incremental sheet forming (ISF) process is an alternative and advanced sheet metal forming technique, well-known due to its flexible and die-less method of forming compared to other traditional forming methods. It is a modern concept-based sheet forming technique adaptive to develop both simple and complicated shapes/components successfully. The clamped metal sheet undergoes small incremental deformations via layer by layer line movement of ball point type hemispherical tool with the help of numerically controlled (NC) user pre-defined definite toolpath. Numerical simulation is an effective method to study the forming process and predict the formability limit in ISF. In this paper, ductile damage failure criteria has been used to investigate the forming limit diagram (FLD) of commercially pure Titanium grade 2 (CP-Ti Gr2) sheet through finite element simulation in ABAQUS (R) software. Truncated conical shape geometry with three different incremental step depth (Delta z) at constant wall angle has been formed. Simulation results of the FLD have been validated and compared with the experimental data from the literature. Finite element analysis (FEA) for predicting the sheet thickness variation along the forming depth and process forming forces also have been carried out. Higher step depth resulted in better formability of the titanium sheet with less sheet thickness reduction. Forming forces (Fz) with smaller step depth showed good results as compared to other two step depths.