摘要
目的以C/C复合材料为基体,设计ZrB_2-SiC功能梯度材料。方法利用Ansys软件对等离子喷涂ZrB_2-SiC功能梯度涂层在沉积过程中产生的残余应力进行数值模拟,分析成分分布指数p和梯度层厚度t对梯度涂层残余应力的影响;并通过基于悬臂梁理论的热应力解析,计算与基体接触的涂层在涂层与基体厚度比λ不同时的残余应力值。结果模拟分析结果表明,在涂层与基体的界面,梯度层的厚度对轴向压应力影响不大,径向压应力和切向应力均随厚度的增加而增大,在边缘区域应力集中较为严重,易产生层间破坏;纯ZrB_2层为表面层,其应力主要为径向压应力,且沿径向逐渐减小至0,到边缘处又突变为拉应力,并随p的增大而减小。对比解析法分析可得两者计算的与基体接触的涂层内部的残余应力随λ的增大都是逐渐降低的,这符合涂层内部的应力分布原理。根据优化设计,获得功能梯度材料在各梯度层厚度d为0.1~0.2 mm,成分梯度指数为4时的热应力变化缓和效果较好。结论基于悬臂梁理论的解析解可以很好地评估热应力,并验证了该模拟的正确性。
The work aims to design ZrB_2-SiC functionally graded materials（FGM） on C/C composite substrate. Numerical simulation was performed to the residual stress of plasma sprayed ZrB_2-SiC FGM by virtue of Ansys software so as to analyze the effects of composition distribution exponent p and gradient layer thickness t on the residual stress of gradient coating. Through thermal stress analysis based on cantilever beam theory, residual stress of the coating contacting the substrate when substrate thickness differed from λ was calculated. According to the simulation analysis results, the FGM layer thickness had little effect on the axial compressive stress in the interface between coating and substrate, while radial compressive stress and tan-gential stress increased as the coating thickness increased. Serious stress concentration was present in the marginal area and might lead to interlaminar failure. On top surface of pure ZrB_2 coating, radial compressive stress was the main stress form, which gradually decreased to zero in the radial direction, suddenly became tensile stress on the edge and decreased as p increased. Compared with analytical method, residual stress of the coating interior contacting the substrate calculated in two methods gradually decreased as λ increased, conforming to the stress distribution principle of coating interior. According to optimization design, optimal thermal stress variation and mitigation effects could be obtained provided that the compositional gradient exponent p=4 and the coating thickness d=0.1~0.2 mm. Analytical solutions based on the cantilever beam theory can be used to evaluate thermal stress favorably and verify correctness of the simulation.
出处
《表面技术》
EI
CAS
CSCD
北大核心
2016年第12期97-103,共7页
Surface Technology
基金
中国科学院特种无机涂层重点实验室开放课题基金资助(KLICM-2013-09)~~
关键词
功能梯度涂层
成分分布指数
残余热应力
有限元分析
functionally graded coatings
compositional distribution exponent
residual thermal stresses
finite element analysis
