Research On Heat Transfer And Numerical Simulation Of Laser Transmission Welding PC Based On Rough Surface

Laser transmission welding has become an indispensable processing method for modern industrial development with the advantages of high welding speed,small heat-affected zone,no residue,and small welding deformation.The thermoplastic laser transmission welding process is a complex process in which the unsteady and uneven temperature field is formed,the mechanical force continues to function,and the plastic flow interacts with each other.The theoretical research based on the ideal contact surface and the analysis of a single physical field can no longer meet the actual production requirements.Therefore,it is necessary to consider the influence of the real rough surface and the multiple physics coupling,which has theoretical significance to further explore the energy transfer and conversion and weld formation during laser welding,and far-reaching practical significance for the development of the automotive industry,aerospace and biomedical equipment manufacturing industries.In this paper,a mathematical model of heat transfer is established based on the three-dimensional(3D)rough surface model of the welding specimen with the research object of polycarbonate(PC).A 3D finite element model based on a rough surface is established to investigate the influence of welding process parameters on the temperature field,flow field,and two coupling fields.A mathematical model between welding process parameters and welding quality is established to optimize welding process parameters.The study is as follows.Firstly,the interaction between the laser beam and the welding specimen in the laser transmission welding process was studied.The transmittance,reflectivity and absorption rate of the PC transparent specimen and the absorption specimen were measured.The reflectivity of the different rough surfaces of the specimen was studied.Secondly,three-dimensional surface reconstruction is used to model the three-dimensional rough contact surface of the welded specimen.The fractal is determined as a three-dimensional surface reconstruction method.Determine the roughness of the rough surface of the welding specimen to evaluate its parameters such as fractal dimension and scale factor.Using the anisotropic three dimensional W-M function to construct the contact surface geometry model and numerical calculation model.And the solid model was established by the three-dimensional software.Again,the response surface methodology was used as the analysis method for welding experimental data and simulation results to establish a mathematical model for the influence of various welding process parameters on the contact thermal conductivity.The range of process parameters about laser power,welding speed,and clamping force is determined by single-factor experiment.The welding experiment was utilized to determine the width of the experimental weld and the contact thermal conductivity was determined by simulation.The mathematical model of heat conduction was established based on the response surface methodology.The regression equation describing the quadratic polynomial empirical model of contact thermal conductivity and welding process parameters was obtained.Compare the forecast results with the experimental results to verify the accuracy of the model.The response surface methodology was used as an optimization method for welding process parameters.A three-factor and five-level test scheme was established.Laser power,welding speed,and clamping force were used as independent variables.The weld strength and weld width at the weld area were used as dependent variables.The mathematical model between the welding process parameters and the welding quality is optimized for the welding process parameters.Finally,ANSYS was utilized to simulate the temperature and flow fields for laser transmission welding of PC.Considering the influence of the optical properties of the PC translucent parts on the laser characteristic,the laser power and the spot diameter of the absorber were measured,and the body heat source model of the absorbed specimen was established according to the interaction between the absorption specimen and the laser.The contact thermal conductivity under different welding process parameters was determined according to the contact thermal conductivity model.The temperature field and flow field of the laser transmission connection PC are simulated and analyzed to determine the influence of welding process parameters on the temperature field and flow field.The research results of this paper provide distinguished help for clarifying the common mechanism of different process parameters in the laser welding process.It has important theoretical significance and engineering application value for the research and development of accurate,efficient,low-cost laser transmission welding process and equipment.It also provides technical support for the wide application of polycarbonate in the industry.