Research On Process And Numerical Simulation Of Laser Transmission Welding PC Based On 3D Real Surface Topography

Laser transmission welding is a kind of non-contact and environmentally friendly welding method with high welding precision,small heat affected zone,high bonding strength,it has become an indispensable processing technology in the development of modern industry.Temperature field in the process of welding is unstable and uneven,the study which based on the ideal contact surface can not satisfy the requirement of practical production,nowadays,in most cases the three-dimensional real morphology contact surface need to be considered.It is of great theoretical and practical significance to study the mechanism of heat generation and energy transfer and the mechanism of energy transfer and conversion,and benefit the further study of the formation,flow,expand the behavior of weld as well for the popularization and application of laser transmission welding technology and equipment design.(1)The surface is polished with five kinds of sandpaper for different surface roughness,sandpaper mesh are 100W,120W,150W,800W,1000W,respectively.Then,the fractal dimension of different surface is calculated,and the relationship between surface roughness and fractal dimension is discussed and the solid modeling is achieved based on the mathematical model of surface roughness profile according to fractal theory to be built.(2)Through response surface method,the mathematical models of the laser transmission maximum break load and welding width are established on the basis of 3D real contact surface.The interactive effects of the welding process parameters on the welding quality is explored.Then,the models are verified and then used to optimize the welding process.At last,the optimal process parameters are obtained.(3)According to the form of laser transmission welding,a special pneumatic clamp for transmission welding is designed.The experiment with a single variable reveals the variation law of the tensile force and the width of the weld with the laser power,welding speed,clamping force,the thickness of the transparent part and the surface roughness changing.The type of fracture is determined based on the observation of the microscopic morphology of the tensile fracture to study on the relationship between surface roughness and welding strength.(4)In order to study the influence of the laser transmission on the laser transmission,the transmission rate of PC with different thickness is studied experimentally.Meanwhile,the influence of surface quality on the near infrared reflectance and absorption is studied.And compared with the theoretical calculations of the absorption rate,in the process of numerical simulation,the effective absorption coefficient of different surface quality is determined.At the same time,the variation of the thermal physical parameters with the temperature is determined,and the finite element simulation is carried out,the results accord with the actual process.(5)Finally,temperature fields in the process of welding two different roughness surface of the polycarbonate are simulated through MSC.Marc.The influence of different grid sizes on the simulation results of the surface temperature field of rough PC is investigated by using the double ellipsoid power density distribution heat source model.The temperature field of the single plate without contact and overlap welding as the contact heat transfer coefficient is considered with a combination of gaussian surface heat source model and a rotation gauss body heat source is studied,the temperature field distribution under different welding parameters and the maximum temperature varies with laser power and welding speed are analyzed.The simulation process is compared with the actual welding results,proving that the model is reliable.