STRESS ANALYSIS USING FINITE ELEMENT METHOD ON SIALON/AISI 430 FERRITIC STAINLESS STEEL JOINT

Ceramic has many good characteristics for high temperature applications such as in heat exchangers. In the actual application of the ceramic to the structures, a ceramic-to-metal joint is unavoidable. This makes joining of ceramic to metal a critically important technology in advanced engineering. However, the fundamental problem in joining of metals and ceramics is the development of residual stresses which originated from the property mismatch between the ceramic and metal. A finite element analysis (FEA) using ANSYS was used to evaluate the residual stresses in the joints. In this analysis, stress analyses were conducted on sialon/AISI 430 joint. The joint was assumed to be perfectly bonded at the interface at 1200°C and stresses developed during cooling down to room temperature. Sequential coupled-field analysis was performed with PLANE55 and PLANE42. Model was simplified to two dimensional (2-D) problems, since its rotation about the axis of symmetry will generate the complete volume of the cylinder.
It was found that the maximum tensile stress occur at the edge of sialon, close to the joint interface. The influence of thickness of sialon, diameter and joint design on the generation of stress in sialon was analyzed. Analyses were made to study the effect of each parameter on stress by varying it, for example, thickness of sialon, while fixing the other parameters. It was found that increasing thickness of sialon and diameter of the joint has resulted in increasing magnitude of tensile stress. The stresses can be reduced by employing symmetrical design joint and incorporating interlayer. The verification of the model was carried out by analytical calculation and comparison with literature review. The results of simulated stresses are in good agreement with the analytical method and literature review.