Experimental Studies And Numerical Simulation On Laser Shock Marking

Laser shock marking is a novel technique which combines of laser shock with marking. Starting from classification of laser marking, the paper introduces several different laser markings and analyses the principal of laser markings. Experimental studies and simulation were carried out on laser shock marking. In this paper, the main contents were as following:Through the changes of laser pulse energy and the material of constrained layers, the experimental schemes of laser shock marking with 6061 Al alloy and AZ91 Mg alloy were designed. For 6061 Al alloy, using water as the constrained layer, black coating as the absorption, the results show that as the amount of the laser energy increases, depth and residual stress of marking zone increases gradually. While plastic deformation occurs, strength and hardness of the material surface increases significantly because dislocation density increases rapidly due to dislocation motion, proliferation and slip. For AZ91 Mg alloy, considering water corrosion to Mg alloy, using K9 glass as the constrained layer, aluminum foil as the absorption, the depth of marking zone does not increase with the increasing of laser pulse energy because of shielding effect of the plasma. Hardness of the material surface increases significantly because of plastic deformation on the material surface.In order to study distributing of residual stress and distortion on the basis of experiments, a FEM model of marking by laser shock waves based on ANSYS/LS-DYNA was established in this paper. By loading the shock waves induced by laser, a numerical simulation on marking had been carried out. The simulated result shows that the mesh of marking zone acted by laser shock waves forms a crater with dimension similar to the diameter of the load, and its residual stress is compressive stress. As the amount of the deformation increases gradually, the residual compressive stress in the center of marking zone reaches the maximum; the residual compressive stress along the thickness of the plate declines as the thickness increases.