Numerical Simulation Study Of Ultrasonic-Assisted MIG Hybrid Welding Droplet Transition Model

In this paper,by analyzing the characteristics of ultrasonic-assisted MIG hybrid welding,the theory of numerical simulation of droplet force and droplet transition,combined with Magnetohydrodynamic theory and Navier-Stokes equation,the UDF(User Define Function)secondary development program is used to perform ultrasonic-assisted MIG Welding(U-MIG)and conventional MIG(Melt Inert-Gas Welding)welding droplet transfer numerical simulation.By establishing a mathematical model of MIG welding droplets under the application of ultrasonic vibration,the characteristics of MIG welding droplets under ultrasonic vibration,transition frequency and other characteristics are explored.The influence law and mechanism of ultrasonic vibration on the transition of MIG welding droplets are analyzed.The hybrid welding method has important theoretical significance and practical value to improve the thin plate welding technology,and also provide theoretical guidance and reference for the formulation of actual production welding processes.Firstly,this article uses the Geometry module of ANSYS18.0 software to establish the ultrasonic-assisted MIG welding droplet transition model,and uses the external interface UDF(User Define Function)of the fluid analysis module Fluent software to conduct a secondary development program to establish the droplet transition model.Secondly,under certain conditions of ultrasonic parameters,FLUENT was used to calculate the droplet transition data under multiple sets of currents,the morphologies of droplets in three different droplet transition modes before and after separation were analyzed,and the ultrasonic vibration The influence mechanism of the droplet transfer,as well as the post-processing function combined with the software,combined with the internal dynamic pressure cloud diagram of the droplet and the X Y velocity scatter diagram of the flow field,are further analyzed and compared.Finally,in order to verify the reliability and accuracy of the simulation results,a verification test was carried out.The dynamic process of the U-MIG droplet transition was photographed using a high-speed camera system and the image data was processed by MATLAB to obtain the droplet size.The simulation results show that the use of the two-phase flow VOF model in FLUENT software can initially achieve dynamic simulation of droplet transfer in ultrasonic-assisted MIG welding,and had achieved certain results.The deformation of the droplet was observed during the transition of the droplet.Compared with the traditional MIG welding,the droplet was axially elongated due to the influence of ultrasonic vibration during the transition and the droplet size decreased.U-MIG welding introduces additional force during the droplet transfer process.The additional force is the transverse shearing force of the ultrasonic vibration on the droplet,which accelerates the droplet transfer rate and makes the droplet drop process deviate from the axial position of the welding wire.In the verification experiment,the image processing method was used to obtain the equivalent radius and the descending height of the droplets.It was found that the simulation result was not much different from the experimental result.The simulation result and the experimental value were in agreement to a certain extent,thus proving the accuracy of the numerical model established in this paper.