An Analysis of a Crack in Functionally Gradient Coatings by Inhomogeneous Finite Element

本文采用非均匀等参有限元的方法研究了薄膜梯度涂层/均匀基材中的界面裂纹问题，并与双材料界面裂纹情况进行了对比计算。研究表明：在均匀基材上采用梯度涂层，与双材料相比可以有效地降低裂尖场应力强度因子；同时还分析了涂层厚度与梯度参数对界面应力强度因子的影响。结果表明：当薄膜厚度大于或等于裂纹长度时，应力强度因子（K_I、K_(II)）对其尺度的变化显得不敏感；对梯度参数的影响而言，当材料性能曲线的幂指数m大于1时，裂尖场的应力强度因子K_(II)相对K_I很小且基本不随m变化，因此裂尖场与均匀材料情况类似；当m小于1时，应用强度因子K_(II)随m减小而急剧增大，裂尖场由K_I及K_(II)控制，断裂趋于混合型

Singularity of Stress Field Around Interface Crack Between Viscoelastic Bodies

研究两半无限大黏弹性体间Griffith界面裂纹在简谐载荷作用下裂纹尖端动应力场的奇异特性。通过引入裂纹张开位移和裂纹位错密度函数，相应的混合边值问题归结为一组耦合的奇异积分方程。渐近分析表明裂尖动应力场的奇异特征完全包含在奇异积分方程的基本解中。通过对基本解的深入分析发现黏弹性材料界面裂纹尖动应力场具有与材料参数和外载荷频率相关的振荡奇异特性。以标准线性固体黏弹材料为例讨论了材料参数和载荷频率对奇性指数和振荡指数的影响

A note for the crack problem of functionally graded materials

Employing the power-type function of material properties, a crack lying between the functionally graded materials (FGMs) and homogeneous substrate is studied by an asymptotic analysis from that of bimaterials, J-integral and the numerical calculations. The present results show that when the curve of the material property is concave, i.e. the power (m) of function of material property is great than 1, the stress distribution near the crack-tip is the same as that of homogeneous materials, which is in agreement with previous findings. However, if the curve of the material property is convex corresponding to 0 & lt; m & lt;1, our results show that the stress distribution is strongly affected by m and it can be obtained asymptotically from that of bimaterials