C/C复合材料钎焊接头应力场的有限元分析

Finite Element Analysis of Stress Field of C/C Composite Brazed Joint

异种材料钎焊接头中的残余应力是接头连接质量低的主要原因之一。本工作基于热-弹-塑性理论,以Abaqus有限元软件为平台,采用数值模拟计算的方法,研究C/C-C/C、C/C-TiAl同种及异种材料钎焊接头残余应力状态,揭示应力分布对接头连接性能的影响。结果表明:不同钎焊接头中,等效应力大小和分布状态不同。同种材料接头中应力集中分布在钎缝和C/C复合材料钎焊面棱角处,从外向内逐渐减小;异种材料接头中,应力集中在靠近钎缝区域的C/C复合材料上,从内向外逐渐减小。影响接头性能的应力主要为钎缝轴向正应力和垂直于轴向的切应力。同种材料接头中残余应力较小,C/C复合材料受轴向拉应力几乎为零,影响其连接性能的主要是切应力。异种材料接头中残余应力较高,C/C复合材料中最大轴向拉应力分布在棱角位置,最大切应力分布在钎焊面内部。

Residual stress in brazed joint of dissimilar materials is one of the main reasons which result in low joint quality.The magnitude and distribution of residual stress in brazed joints of C/C composite and C/C composite,C/C composite and TiAl alloy were studied by numerical simulation method based on thermal-elastic-plastic theory and finite element software Abaqus as a platform.Furthermore,the influence of stress distribution on joint performance was revealed.Different Von Mises stress distribution and state appeared in different brazed joints.In C/C-C/C brazed joint,Von Mises stress was concentrated at the brazing seam,the edges and corners of C/C composite’s brazed surface,and gradually decreased from the outside to the inside.In C/C-TiAl brazed joint,the stress was concentrated on C/C composite where adjacent the brazing seam,and gradually decreased from inside to outside.The joint strength of brazed joint was mainly affected by the axial normal stress and the shear stress perpendicular to the axial direction.The residua stress of C/C-C/C brazed joint was lower,its axial tensile stress was almost zero,therefore the join strength of brazed joint was mainly affected by the shear stress.The residual stress of C/C-TiAl brazed joint was much higher,in C/C composite the maximum axial tensile stress was distributed at the edges,and the maximum shear stress was distributed inside of the brazed surface.