Simulation Analysis Of Gas-Liquid-Solid Coupling In Laser Induced Manufacturing

Laser is a kind of high accuracy,high stability,high efficiency processing tool for manufacturing.In laser induced manufacturing,the high pressure plasma produced by laser is often used as an important medium materials processing.As a result,the mechanism of laser-induced plasma(LIP)is very important in laser-induced manufacturing.In this thesis,series of gas-liquid-solid coupling simulations and experiments have been executed to study the mechanism of the LIP in laser-induced forward transfer(LIFT)and laser shock peening(LSP).The main contents and results of the study include:1)By theoretical analyzing the generation and propagation of LIP,and regarding the actual processing situation,a physical model of two-phase flow is proposed to simulate LIFT process,meanwhile a transient gas-liquid-solid coupling model is proposed to simulate LSP process.In these models,the lattice Boltzmann method developed from the lattice gas automata are used.It can deal with the flow and evolution of complex fluid interface,especially suitable for simulating the fluid evolution in LIFT.2)In the simulation of the LIFT process,the Rayleigh-Plesset equation is used to describe the evolution of LIP bubble,and the inlet boundary condition of massflow for the two-phase flow model is obtained.The flow volume change of L IP bubble in LIFT process is controlled.Under the condition with and without receiving layer,the forward transfer and deposition process of conductive silver paste under different laser energ ies are studied.Three different transfer and deposition states were obtained and analyzed systematically.More importantly,the phenomenon of backward transfer in the LIFT process of alginate solution is simulated.The process and principle of the reversal transfer of alginate solution in the LIFT were revealed.3)In the LSP,transient gas-liquid-solid coupling model is utilized.First,under the condition with and without water confined layer,the pressure in the basin,the pressure distribution,the propagation mode of the pressure and the stress response in the structure are compared under the same pressure LIP bubble as the initial condition.The conclusion of the shock wave restraint and strengthening effect of water confined layer is obtained.Second,the value,distribution and propagation mode of the residual stress in the structure are obtained by using the pressure LIP bubble which far exceeds the yield strength limit of the material as the initial condition.4)According to the simulation results of LIFT Under the condition with and without receiving layer,the corresponding experiments are also carried out using conductive silver paste as target.Starting from the process of transfer,the state of deposition,the removal of materials on the target substrate and the morphology of the deposition point,the process of silver paste transfer is photographed by high speed photography,and the deposition point was observed using the hyperfield microscope.The results illustrate that the simulation results agree well with the experimental results,which proves the simulation model and the method is acceptable.An analysis of the simulation errors is provided and the end.