Brazed residual stress in a hollow-tube stacking: Numerical simulation and experimental investigation

Abstract

In this study, the residual stresses of a hollow-tube stacking made of 316L stainless steel by brazing technology have been analyzed by finite element method and X-ray diffraction method. The results show that simulated results are in good agreement with the experimental data, reflecting the feasibility of finite element method to calculate the residual stress. Large tensile stresses are generated in the brazing filler metal, decreasing the cooling rate can decrease the residual stress. With the tube diameter, brazing filler metal thickness increasing, or tube length decreasing, the residual stresses in the filler metal decrease. Increasing the wall thickness can decrease the transverse stress at the middle region of the brazing filler metal, while it can increase the longitudinal stress at the vicinity of brazing fillet. The matrix size of the hollow-tube stacking has little effect on the stress distribution of the 316L/BNi-2 brazed joint. When the tube diameter is increased to 8mm, the residual stress in the fillet transforms into compressive stress and thus can decrease the cracking sensitivity in the fillet. It is proposed that the diameter of tube should not be less than 8mm from the viewpoint of generating compressive stress.