Numerical modeling of pressure resistance welding of zirconium alloy tube-end plug joint.

The zirconium alloy cladding tube and end plug used for nuclear fuel rods are usually joined by pressure resistance welding. And the service performance of the fuel rod cladding is directly influenced by the welded joint. In order to understand the forming process deeply, an axisymmetric electro-thermal–mechanical process finite element model was established in this paper. The current density distribution, temperature field evolution, and joint forming process during pressure resistance welding were all simulated by this model. It was shown that due to the contact resistance, a concentrated heat flow was rapidly generated on the tube-plug contact surface caused by welding current. A heat conduction was established on both sides of the welding surface. The high-temperature region on the side of the cladding tube was larger than the end plug. The metal of the tube extruded to both inside and outside of the joint under the coupled loading of heat and pressure. The location of the highest instant temperature on the welding surface moved from the inside to the outside of the joint. The highest temperature was 1568 °C, not reaching the melting point of zirconium alloy. The joining area and the highest temperature increased with welding current increasing, the welding time had little effect on them. Based on the numerical model, two structural design schemes to improve the joint forming quality were proposed. They were expected to provide a guide line for the joint design. [ABSTRACT FROM AUTHOR]