Refill friction stir spot welding (RFSSW) is a solid state joining technology that has the potential to replace processes such as the open-air fusion bonding technique and rivet technology in aerospace applications. Selection of proper RFSSW parameters is a crucial task which is important to ensure the mechanical strength of the joint. The aim of this paper is to undertake numerical modelling of the RFSSW process to understand the physics of the welding process, which involves large deformations, complex contact conditions and steep temperature gradients. Three-dimensional fully coupled thermo-mechanical models of RFSSW joints between Alclad 7075-T6 aluminium alloy sheets have been built in the finite-element-based program Simufact Forming. The simulation results included the temperature distribution and the stress and strain distributions in the overlap joint. The results of numerical computations have been compared with experimental ones. The numerical model was able to predict the mechanics of material flow during the joining of sheets of Alclad aluminium alloys using RFSSW. The predictions of the temperature gradient in the weld zone were in good agreement with the temperature measured experimentally. The numerical models that have been built are capable of simulating RFSSW to reduce the number of experiments required to set optimal welding parameters.

补充摩擦搅拌点焊（RFSSW）是一种固态连接技术，具有替代航空航天应用中的露天熔合技术和铆钉技术等工艺的潜力。选择合适的RFSSW参数是一项至关重要的任务，这对于确保接头的机械强度非常重要。本文的目的是对RFSSW过程进行数值建模，以了解焊接过程的物理过程，该过程涉及大变形，复杂的接触条件和陡峭的温度梯度。Alclad 7075-T6铝合金板之间的RFSSW接头的三维完全耦合热机械模型已在基于有限元素的程序Simufact Forming中建立。仿真结果包括搭接接头的温度分布以及应力和应变分布。数值计算的结果已经与实验结果进行了比较。该数值模型能够预测使用RFSSW连接Alclad铝合金板时的材料流动力学。焊接区温度梯度的预测与实验测得的温度吻合良好。已建立的数值模型能够模拟RFSSW，以减少设置最佳焊接参数所需的实验次数。该数值模型能够预测使用RFSSW连接Alclad铝合金板时的材料流动力学。焊接区温度梯度的预测与实验测得的温度吻合良好。已建立的数值模型能够模拟RFSSW，以减少设置最佳焊接参数所需的实验次数。该数值模型能够预测使用RFSSW连接Alclad铝合金板时的材料流动力学。焊接区温度梯度的预测与实验测得的温度吻合良好。已建立的数值模型能够模拟RFSSW，以减少设置最佳焊接参数所需的实验次数。