Finite Element Analysis Of The Temperature, Distortion And Stress Fields In Underwater Wet Welding

For manufacturing of ocean engineering structures underwater wet welding has great application prospects, since its low cost, and good adaptability. In underwater wet welding, the welded materials contact water directly, and the arc generates in water and maintains in bubbles. In high pressure and strong cooling underwater environment, the pressure, shape and energy density of the welding arc change, and the more notable changes of workpiece cooling conditions take place. Therefore, modeling the process mechanism of underwater wet welding, and analyzing the effect of underwater environment on the temperature field, stress and distortion of weld joints are of important theoretical and practical significances.Firstly, an arc-droplet heat source acting model with proper heat density distribution parameters is established for conventional GMAW process operating in land. In this model, the downward and backward heat transfer caused by the pool surface depression and backward fluid flow of liquid metal in the weld pool have been considered indirectly. And the welding temperature, stress and distortion fields under different process conditions are numerical simulated. Weld pool and bead profile and size, welding thermal cycle, and the stress and distortion are calculated. The model is experimentally validated and found good adaptability to simulate the conventional GMAW process.The numerical analysis model and heat source model of conventional GMAW are improved, and the heat density distribution parameters are varied in order to adapt to the specific process features of underwater welding. Then, appropriate model of the temperature field and thermal process is established for underwater wet welding. And weld pool and bead profile and size, welding thermal cycle and so on are calculated under different water depths and different water velocity are obtained. Combine the thermal model and the stress-distortion model, the coupling thermal-mechanical simulation is realized for underwater wet welding. For several study cases, the residual stress and distortion data are obtained. The effect of underwater environment on the distortion and stress field is analyzed.