Level-Set Method Based Keyhole Tracking In Plasma Arc Welding

In keyhole plasma arc welding (PAW) of middle-thickness plates, forming of the keyhole is the key issue to attain deep penetration and weld with large aspect ratio. The behavior of the keyhole in weld pool is an important factor to affect the stability of weld formation and the quality of weld joint. Therefore, to do further study on dynamic behaviors of keyhole in PAW and to track and describe the keyhole interface with proper methods are of great significance for optimizing the welding parameters in PAW, improving the robustness of the PAW welding process and enhancing the stability of weld quality.From the point of view in macroscopic phenomena of heat transfer, the keyhole effect is described through developing an adaptive heat source mode. The mathematical model of weld pool in stationary PAW and moving PAW systems are developed. By analyzing the theory of Level-Set method and characteristics of PAW process, Level-Set method is used to trace the dynamic evolving process of keyhole in PAW.The process of keyhole development in both stationary PAW and moving PAW are numerically simulated through establishing the fluid flow fields in both the plasma and weld pool. The information on shape and size of both weld pool and keyhole at different instants is obtained under a few welding conditions. According to detection of the efflux plasma voltage signal when a complete keyhole is established, the predicted results are verified by PAW experiments.