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

Abstract

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.

Study on Peeling Performance of T-Type Brazing Joints Based on Energy Method

“…Some scholars have tried to calculate the plastic dissipation energy with mathematical methods. Georgion and Kawashita [32][33][34] et al obtained that the critical cohesive energy G c can be estimated via Equation (4) under the assumption that the base metal is elastic-plastic material.…”

Interface strength investigations of 304 stainless steel/T2 red copper T-type brazed joint based on cohesive zone model

“…The base metal uses the plane strain element CPE4R, and material parameters were determined according to table 3. The plastic behavior of 304 stainless steel was obtained according to the literature [18]; the interface layer uses the twodimensional cohesive element COH2D4, the parameters of which are defined in the next section. The base metal and the interface layer use Tie binding, the lower end of the model uses fixed constraints, and the upper and lower ends of the specimen apply horizontal constraints, vertical static and cyclic displacement loads were applied on the upper end of the model.…”

“…Wei [17] experimentally obtained the fatigue life of a 30CrNi2MoV material, verified the simulation accuracy based on cyclic CZM, and predicted the fatigue crack growth of the fracturing pump. Zhou [18] used an SS304/BNi-2 brazed joint to carry out tensile tests to obtain the critical fracture energy, determined the critical stress of the brazed joint by comparing simulation and test results, and predicted the peeling process of a brazed joint using CZM.…”