金属/陶瓷发热体直接钎焊接头的应力分析

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的情况下,分析了采用Ag-Cu-Ti钎料钎焊Al2O3陶瓷与镍金属丝的钎焊接头,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.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.并指出钎料性能参数是决定有限元计算精度的主要因素,要使计算结果与实际情况尽量符合,钎料性能参数的正确选择是关键.

Residual stresses in brazed joints of ceramic-metal heater

Thermal elastic-plastic FEM was used to analyzed the residual stresses in the brazed joints of Al_2O_3 ceramic and metal of Ni with considering 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 filler metal of Al-Cu-Ti on the residual stresses was emphatically concerned in FEM calculations.The analytical results showed that the residual stresses in the interface are high and they result in the decrease of joint strength,sometimes even some cracks will create near the side of ceramic in the interface as shown by the experimental result.Therefore,it may be concluded that the filler metal is the main factor in producing residual stresses in this type of joint.It was also indicated that the used property data of filler metal are the main factors affected the precision of FEM calculation.