Numerical simulation of residual stresses in brazed ring joint between SiO_2f/SiO₂ composite and Nb metal

The residual stress in brazed ring joints between SiO_2f/SiO₂ composite and Nb along radial direction was numerically simulated with finite element method. According to simulation results, there were large radial tensile stress σ_y and circumferential shear stress τ_yx in the brazed joint, and the peak values were 1 047 MPa and 329 MPa respectively. Moreover, there was obvious stress concentration at the side of SiO_2f/SiO₂ composite adjacent to the brazing seam, which was the weakest site that damage will preferentially occur during the cooling stage. The residual stress can be mitigated effectively by cutting narrow grooves at the jointed surface of SiO_2f/SiO₂ composite, and the peak values of σ_y and τ_yx were reduced to 731 MPa and 230 MPa respectively. In comparison with the condition with no groove cutting, the σ_y and τ_yx near surface at the side of SiO_2f/SiO₂ composites adjacent to its interface with brazing seam were reduced from 200 MPa to 81 MPa and from 230 MPa to 53 MPa respectively. The significant mitigation of residual stress in brazed joints caused by groove cutting is very beneficial to avoid the crack and to improve the joint strength as well as the joint reliability.