An adaptive heat source model for finite-element analysis of keyhole plasma arc welding

An adaptive model of the heat source in numerical simulation of the keyhole plasma arc welding (PAW) requires that the model take into consideration the larger aspect ratio of welds and the volumetric distribution characteristic of heat intensity along the direction of the plate thickness. The available heat source models, either planar one like Gaussian or body ones like double-ellipsoidal and rotary Gaussian modes, are unable to describe the keyhole PAW process accurately. Based on the configuration feature of keyhole PAW welds, a combined heat source model is proposed for the numerical analysis of temperature fields in keyhole PAW process. It accounts for the keyhole effect indirectly and the volumetric distribution characteristics of plasma heat intensity along the direction of the workpiece thickness. With this adaptive heat source model, finite-element analysis of temperature profile in keyhole PAW is conducted and the weld geometry is determined. The results show that the predicted geometry and locus of the fusion line in the keyhole PAW weld cross-section are in good agreement with the experimental measurements. It lays solid foundation for the process optimization, metallurgical analysis and thermal stress-strain simulation of keyhole PAW process.