金属/陶瓷发热体钎焊接头的残余应力分析

采用热弹塑性有限元方法，在考虑了材料性能参数随温度变化情况下，分析了采用Ag—Cu—Ti钎料钎焊A12O3陶瓷与Ni金属丝的钎焊接头，在钎焊和随后再次加热过程中产生的应力大小和分布情况，计算中着重考虑了钎料对接头残余应力的影响。分析结果表明，在钎料与陶瓷的界面处存在着较大的残余拉应力，影响了钎焊接头的连接强度，并可能在界面的陶瓷侧产生裂纹。通过试验对比，认为在此类连接结构中，钎料是造成接头形成较大残余应力的主要因素。同时。选择合适厚度的钎料会降低钎焊接头的残余应力，改善接头连接强度。

Residual Stresses in Brazing Joints of Ceramic -Metal Heater

Thermal elastic-plastic FEM was used to analyze the residual stresses in the brazed joints for Al_2O_3 ceramic-metal Ni with the considering of the variation of material properties with temperature. In the process of brazing and reheating of the joints, the residual stress was induced and compared. The influence of brazing metal Al-Cu-Ti on the residual stresses was emphatically concerned in FEM calculations. The analytical results show that the residual stresses in the interface are high and it results in the decrease of joint strength, sometimes even produces some cracks in the side of ceramic near the interface as shown as the experimental result. Therefore, it may be concluded that the brazing metal is the main factor in producing residual stresses in this type of joint. Choosing a appropriate thickness filler metal for brazing metal-ceramic can decrease the residual stresses in the brazed joints and improve the joint strength.