Title

Thermal modeling of advanced manufacturing technologies: Grinding, laser drilling, and solid freeform fabrication

Date of Completion

January 1998

Keywords

Applied Mechanics|Engineering, Mechanical|Engineering, Metallurgy

Degree

Ph.D.

Abstract

Thermal modeling of grinding, laser drilling, Selective Laser Sintering (SLS), and Selective Area Laser Deposition (SALD), are presented in this dissertation. A thermal model of the grinding process, which includes submodels for the abrasive grain, fluid, and workpiece, was developed by using the integral approximation method. For cases without film boiling in the grinding zone, the calculated workpiece background temperature rise agreed very well with previous models. It can also correctly simulates the grinding process when film boiling occurs in the grinding zone. ^ Vaporization and melting during the laser drilling process are investigated analytically. The dependence of saturation temperature on the back pressure and the conduction heat loss to the solid are also considered. The predicted material removal rate agreed very well with the experimental data. The effect of conduction heat loss for different laser properties on the vaporization and melting in the laser drilling process is investigated. ^ Three thermal models of the SLS for a two-component metal powder bed were proposed: (1) 1-D melting of the powder bed with constant heat flux heating; (2) 2-D melting and resolidification of a powder bed with a moving Gaussian heat source; (3) 3-D melting and resolidification of a powder bed with a stationary ellipsoid or a moving round laser beam. The shrinkage of the powder bed was taken into account in all three models. The liquid flow driven by capillary and gravity forces was considered in the 3-D model. The predicted temperature history and the shape of the sintered part are compared with experimental results and the agreements are satisfactory. ^ Finally a thermal model of SALD of Titanium Nitride with stationary or moving laser beam, which accounted for heat transfer in the substrate and gases, chemical reaction on the substrate top surface, and mass transfer of gases in the chamber, is presented. For the cases of stationary laser beam, the predicted deposited film profile is in good agreement with the experimental results. For the case of moving laser beam, the effects of laser beam intensity and scanning velocity were investigated. ^