Determination Of The Parameters Of Double Ellipsoid Heat Source Model And Its Application In Simulation Of Multi-pass Welding

With the increase in the diversity of welding structures,materials,and conditions of use,the requirements for welding quality have become higher and higher.In view of the large number of influencing factors on welding quality and complex test methods,welding simulation has become an effective method for related research.The welding heat source model is a key factor affecting the accuracy of the simulation results.At present,the most widely used in melt-welding simulation is the Goldak's double ellipsoid heat source model,but due to its constant heat flux distribution parameters,the application in some welding processes is not ideal.In order to solve this problem,multi-pass welding experiments with a variety of typical weld pool shapes were designed in this paper.The influence of model parameters on the simulation results of temperature field was studied using numerical simulation methods.The comparison between experimental and numerical simulation results was carried out to explore how to obtain model parameters for better simulation results.The main work and conclusions are as follows:(1)Based on the classical Goldak's double ellipsoid heat source model,the numerical simulation of the temperature field of the welding process was carried out and compared with the verification experimental results.It was found that this model can only simulate the shape of the molten pool with relatively moderate ellipticity.Then,based on the second pass simulation parameters with better simulation results,the general expression of double ellipsoidal heat source model(DEHSM)was studied and its parameters were classified into three categories:shape parameters(a,b,c_f,c_r),heat input parameters(?,f_f,f_r),heat flow distribution parameter(?),respectively,summing up the influence of each parameter in the model on the simulation results of the temperature field.The results show that all the three types of parameters have a large influence on the simulation results of the temperature field.Take the actual molten pool size as shape parameters can get the best simulation results.For different molten pool shapes,properly adjust the welding thermal efficiency and the heat flux distribution parameter can optimize the results closer to the actual situation.(2)The mechanism of the influence of welding heat efficiency and heat flux distribution parameters on numerical simulation was studied.The results show that the welding thermal efficiency changes the simulation results by changing the heat input,while welding heat flow distribution parameters mainly change the concentration degree of energy.Taking into account the rules of the effect of these two parameters on the peak temperature,weld width,penetration depth and heat affected zone width of the weld,empirical formulas that are suitable for the test conditions in this paper is established,which lays the foundation for the promotion of the general expression of DEHSM.(3)Based on the above research,the general expression of DEHSM was applied to the temperature field simulation of multi-pass welding.Comparing the simulation results based on the classic Glodak double ellipsoid heat source model,it is found that the optimized model can effectively simulate a variety of typical weld pool shapes and obtain good fit.It is also possible to simulate a so-called"bowl-shaped"or"nail-shaped"weld pool,which provides a new simulation direction for laser welding,electron beam welding,and the like.