A numerical study on laser forming of titanium plates

Laser forming of titanium plates has been studied numerically using finite element computer codes. This paper includes the results for both 0.25” and 0.125” thick plates. The thermal code TOPAZ3D and the mechanical code LS-NIKE3D were used in this study. Together, these two codes provide both the temperature profiles inside the plate and the shape of the plate throughout the entire laser forming process. The titanium plate considered was 12”×12”, and the laser beam moved at 20 cm/min along a straight line across the middle of the plate. The intensity profile of the 2 cm diameter laser beam was based on the measured profile of a ∼2.5kW Nd: YAG laser beam. TOPAZ3D code predicts that the peak surface temperature of the plate exceeds 1800 °R (1000 °K). After cooling down to near room temperature, the LS-NIKE3D code predicts that the plate is formed into a “v” shape symmetric with respect to the laser path. The laser formed angle, or the angle of the “v” shape, changes along the laser path. The 0.25” and 0.125” plates show different dependencies of the laser formed angle on peak surface temperature or laser power. The portion of the plate directly under the laser path also distorts differently depending on the plate thickness and peak surface temperature. Comparison between predicted laser formed angle and experimental data has been carried out for one particular condition with reasonable agreement. The effect of multiple laser passes is also discussed.