Crack Propagation of SS304/BNi-2 Brazed Joints: Experiments and Numerical Simulations

The strength of brazed joints is of great significance for plate-fin heat exchangers. Although a lot of research on the strength of brazed joints has been carried out, few studies have focused on the whole process of the crack propagation of brazed joints under loading, and no accurate simulation methods have been published. In this paper, the crack propagation of SS304/BNi-2 brazed joints was investigated by both experiments and numerical simulations. The cohesive zone model (CZM) was applied to simulate the crack propagation. The cohesive energy was obtained by the T-type brazed joint peeling experiments. The cohesive strength was determined as 30 MPa by comparing the load–displacement curves from the simulations and experiments. The results showed that the crack propagation process predicted by the CZM was consistent with the experimental results. Furthermore, with the increase of displacement applied on the specimen, the rate of crack propagation of the brazed joints was high at the beginning, and then gradually slowed down in the later stages. Under displacement-controlled conditions, increasing the thickness and the yield strength of the base metal could delay the crack initiation, but it would increase the crack growth rate once the crack was initiated.