Prediction of Braze Joint Strength of Dissimilar Materials by Numerical and Experimental Methods

Most highthrust rocket engine thrust chambers have double walled construction enabling them to be regeneratively cooled. One such thrust chamber being developed by ISRO has an inner wall made of a special grade Copper alloy that is brazed to outer wall made of high strength Stainless Steel. The brazing method is selected as the joint is to be formed between dissimilar materials.This paper discusses the theoretical simulations and experimentscarried out to evaluate the strength of braze joint between Copper alloy and high strength Stainless Steel. A test article having similar channel configurations is usedtosimulate the most severe load condition experienced by the joint. The behaviour of this test article is studied using finite element simulations to know its failure mode and predict the failure load. The analysis is performed using ANSYS FEA software using kinematic hardening plasticity material model based on stress-strain curves obtained from specimen level tension tests for both materials, at room temperature condition. Test article is fabricated and pressure test is carried out to evaluate the actual failure pressure of the test article. It is observed that deformation pattern and the failure mode obtained from the simulation has good match with that of the experimental results. The methodology can be used to predict the behaviour of braze joints for similar material combinations.