功能梯度夹层多个环形界面裂纹扭转冲击

研究位于功能梯度层和外部均匀材料之间多个环形界面裂纹的扭转冲击问题,功能梯度材料 (FGM)粘结在两种不同的弹性材料之间，功能梯度层和外部材料之间环形界面裂纹的数目是任意的．引进积分变换和位错密度函数将问题化为求解Laplace域里标准的Cauchy奇异积分方程，进而化为求解代数方程；应用Laplace数值反演技术，计算时域里的动应力强度因子(DSIF)．考查了结构几何尺度和材料特性对裂尖动态断裂特性的影响．数值结果表明，DSIF存在一个主峰，到达主峰后，在其相应的静态值附近波动并最终趋于稳定；增加FGM的梯度能减小DSIF的峰值．

Torsional impact response of multiple cylindrical interface cracks between a functionally graded interlayer and homogeneous material

In this paper the problem of multiple cylindrical interface cracks located between a functionallygraded material(FGM)interlayer and its external homogeneous cylinder subjected to torsional impact loading isinvestigated.The FGM interlayer is assumed simultaneously to bond two coaxial dissimilar homogeneous elasticcylinders,and the shear modulus and mass density of the FGM interlayer are assumed to vary continuouslybetween those of the two coaxial materials.The number of cylindrical interface cracks is arbitrary.Themixed boundary value problem is at first reduced to a singular integral equation with a Cauchy type kernel inthe Laplace domain by applying Laplace and Fourier integral transforms and introducing dislocation densityfunction.The singular integral equation is then solved numerically.The dynamic stress intensity factor(DSIF)is also obtained by a numerical Laplace inversion technique.The DSIF is found to rise rapidly to a peak,then oscillate and tend to the static value.The influences of geometric configuration of the cracks and relativemagnitudes of the adjoining material properties are examined.It is found among others that the DSIF can begreatly reduced by increasing the FGM gradient.