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 Al₂O₃ 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.