SiO2f/SiO2复合材料与金属铌环形钎焊接头的残余应力数值模拟

对陶瓷基复合材料SiO_2f/SiO₂与金属铌环形钎焊接头的残余应力进行了有限元数值模拟.结果表明，接头存在较大的径向拉应力σ_y和周向界面剪切应力τ_yx，其峰值分别为1 047 MPa和329 MPa.靠近焊缝的SiO_2f/SiO₂中存在应力集中，因而在焊后冷却过程容易首先破坏.在SiO_2f/SiO₂连接面表层加工沟槽可有效缓解残余应力，σ_y和τ_yx峰值分别降低到731 MPa和230 MPa.与不开槽钎焊比较，在靠近焊缝界面的SiO_2f/SiO₂侧表层，开槽钎焊使σ_y从200 MPa降至81 MPa、τ_yx从230 MPa降至53 MPa.陶瓷被焊表面开槽之后再钎焊填入钎料所引起的应力缓解，对于避免开裂、提高接头强度及可靠性十分有利.

Numerical simulation of residual stresses in brazed ring joint between SiO2f/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.