Simulation Of Continuous-Pulsed Double-Laser Heat Source Riveting Welding Of Magnesium Alloy-Carbon Fiber Heterologous Material

Modern industrial production of lightweight materials has become a top priority nowadays along with the increasing awareness of environmental protection.Magnesium alloy has the advantages of low density,high strength and good rigidity,which is one of the ideal lightweight materials widely used.Carbon fiber-reinforced resin-based composite（CFRP）also has excellent strength,fatigue resistance and corrosion resistance,and is an important lightweight material.Because of the huge difference of physical and chemical parameters between the two materials,it becomes an important challenge to connect them.Thus,in this thesis,a new heat source with a combination of continuous-pulsed dual laser with high energy density and stability is used,supplemented by rotary riveting welding as a process to realize an effective combination between the two.However,the double laser heat source is difficult to match the welding process characteristics and requires a high degree of precision,making it difficult to achieve accurate control of the melt pool through experimental control of the parameters.Therefore,this thesis will use simulation means to study magnesium alloy and carbon fibre reinforced resin matrix composites（CFRP）as the research object,using continuous-pulse dual laser heat source riveting technology,to establish the experimental conditions of this thesis under the welding temperature field model,and verify the accuracy of the model.The main study of different composite heat source parameters（continuous laser power,pulsed laser power,welding speed,pulse width）on the influence of the change in the welding temperature field,the optimization of parameters.And to explore the influence of each parameter on the shape of the melt pool law,analysis of the melt pool forming effect.Further study of the composite heat source parameters on the melt pool shape of the proportion of the relationship to determine the impact of the core parameters of the melt pool shape,the establishment of this thesis under the experimental conditions of the melt pool shape database,the proposed control method,and the level of regulation,to achieve accurate control of the melt pool depth and width of the melt.The simulation shows that the dual laser composite heat source riveting method achieves a solid connection between magnesium alloy and carbon fiber sheets.Based on the COMSOL simulation software to establish a model of composite heat source riveting welding,the simulation of the pulsed laser a cycle of the welding temperature field cross-sectional diagram and the three stages of the whole welding process can be seen,continuous-pulsed dual laser compound heat source riveting welding melt pool as a whole shows the width of the"conical nail"shape,and the actual The experimental melt pool shape is basically the same,the error is small（1.2%of the melt depth,1.1%of the melt width）,to prove the accuracy of the simulation results.From the complex heat source parameters on the impact of the welding temperature field analysis can be seen,the best of the welding process parameters:continuous laser power 500 W,pulsed laser power 200 W,welding speed of 850 mm·min^-1,pulse width 4.5 ms.By further study of the composite heat source parameters on the shape of the melt pool can be seen,the impact on the melt depth of the relationship between the proportion of:continuous laser power is the core factor,pulsed laser power is an important Factors,while the welding speed,pulse laser width is a minor factor.The influence on the melt width is proportional to the continuous laser power is the core factor,the pulsed laser width is an important factor,and the pulsed laser power,welding speed is a minor element.Hence,the core parameters for controlling the melt pool shape are:continuous laser power,pulsed laser power,pulsed laser width,and welding speed.Based on the four core parameters,the melt pool shape library is established,the proposed melt pool control mode,and the actual pilot melt pool shape for comparison,to determine the accuracy of the control method,to achieve accurate control of the melt pool shape.