| The increasing requirement for laser in material processing can be attributed to its distinct advantages over traditional processing, such as reduced processing cost, higher productivity, non-contact processing, improved product quality, higher material utilization, and minimum heat-affected zone. Numerical simulations combined with reasonable experimental design are implemented for understanding the thermal, mechanical, and metallurgical behaviors in laser-based material processing. Three typical topics including laser welding, laser heat treatment and laser cladding are studied in detail.;An experiment-based finite element model is developed to investigate the thermal field of hybrid laser-arc welding, involving the influence of nonlinear material properties and the variable location of the laser head and arc torch. Optical microscopy and thermocouples are used to validate the numerical model. In addition, a thermo-mechanical finite element model is developed to investigate the transient thermal stress and residual stress distributions in the hybrid laser-arc welding process. The effect of arc preheating on the weld geometry and the level of thermally induced stress and its distortion in the welded joint is also studied. The X-ray diffraction technique is used to measure the residual stress of welded coupons.;A transient multiphase unified mathematical model with experimental validation is also developed to investigate the temperature field, and flow velocity field of the liquid phase in the laser-based multilayer cladding of H13 powder onto a substrate of AISI 4140 steel. The effects of the laser power, scanning speed, and powder feed rate on the geometry of the clad are studied. The relevant experiments are also performed to validate the numerical modeling.;From another view, a finite element method (FEM) combined with a Monte Carlo (MC) model is developed to further study the grain growth in the heat-affected zone (HAZ) during laser heat treatment, in which the heat transfer process is analyzed by FEM and the grain growth is simulated by a MC model. The 3D heat transfer model provides the temperature data for the MC simulation. |
