Numerical Simulation Of Laser Surface Microstructure Processing

As the surface microstructure can improve the friction,biomedical and optical properties of materials,it has a wide range of applications in microelectronics,national defense,biology,advanced manufacturing and other high-tech fields.There are many kinds of surface micro structure machining technology,among which laser is the heat source.Because of its excellent controllability,high efficiency,wide range of application,small pollution and other advantages,it has attracted more and more attention and use.At present,there are many experimental researches on laser surface micro structure machining,but because the experimental phenomena are complex,it is not enough to study the laser surface micro structure machining process only by analyzing the experimental results.Therefore,some numerical simulation is needed to study the thermal and mechanical effects of the material deformation process,and explain the interaction mechanism process between laser and material.Based on the extensive application of surface microstructure,a two-dimensional finite element model based on temperature dependent surface tension is established by using COMSOL finite element analysis software.The influence of surface tension normal stress and surface tension tangential stress on the surface morphology in the process of laser material interaction is studied.On the basis of this theoretical study,the influence of laser energy density distribution on the surface topography is studied,and the numerical models of Gaussian and uniform laser energy density distribution are established.Through the observation of the numerical simulation results,the following conclusions are drawn:1.In the process of laser surface microstructure processing,the positive and negative of the surface tension tangential stress gradient has a significant effect on fluid flow,surface peak temperature and surface morphology.When the surface tension tangential stress gradients are greater than zero,less than zero,and equal to zero,respectively,the changes in the surface morphology of the molten pool are the middle convex edge depression,the middle depression edge protrusion,and basically no change.And in the case where the surface tension tangential stress gradient is lessthan or equal to zero,as the absolute value of the surface tension gradient increases,the fluid velocity on the surface of the molten pool gradually increases,the peak temperature gradually decreases,and the surface morphology deforms more;on the contrary,when the surface tension cuts When the stress gradient is greater than or equal to zero,as the absolute value of the surface tension gradient increases,the fluid velocity on the surface of the molten pool gradually increases,the peak temperature gradually increases,and the surface deformation becomes larger.2.The surface tension normal stress also has a great influence on the surface morphology.The surface velocity of the molten pool gradually decreases with the increase of the surface tension normal stress,the peak temperature gradually increases,and the surface morphology deformation decreases;while the surface temperature of the molten pool surface gradually decreases with the increase of the surface tension normal stress.When the surface tension normal stress increases to a certain value,the peak temperature tends to stabilize.3.The distribution of laser energy density during laser surface micromachining has a great influence on the surface topography.The laser energy density under Gaussian distribution conditions is larger than that under uniform distribution conditions,and it is not easy to determine the specific location of the surface deformation after solidification of the molten pool;while the laser energy density under the uniform distribution conditions changes less in the molten pool interval The position of the surface deformation after curing is easier to determine,and the position of the surface deformation section is close to the diameter of the laser beam.