压电材料中的微裂纹屏蔽问题分析

分析当主裂纹与一个微裂纹在远场I型力（KI）和远场电位移（Ke)作用下的相互干涉问题，得出了在微裂纹的位置角和方向角周时独立变化时，微裂纹对主裂纹的屏蔽作用的全局使命主裂纹扩展，通过电算还发现Ortiz在各向同性材料和各向异性材料中得出的“微裂纹群对主裂纹最大屏蔽效应产生在微裂纹方向与最大主应力垂直的方向”在压电材料中不再成立，进而提出除Hutchinson指出微裂纹屏蔽效应两个来源（即：材料有效刚度的降低和残余应力的释放）外的另一个来源，微裂纹对主裂砂电场的扰动，在对主微裂纹J积分分析时发现J2积分与J1积分具有同等重要的地位。

CRACK TIP SHIELDING BY MICROCRACKING IN PIEZOELECTRIC MATERIALS

Numerical solutions are obtained for the interaction problem between a main crack and an arbitrary located and oriented lmicrocrack near the main crack 1tip under combined Mode I and electric loading conditions. It is found that the positive electric loading promotes the main crack propagation while the negative electric loading retards the main crack propagation in multi- microcrack shielding problems. By virtue of numerical evaluations, it is found that the conclusion obtained by Ortiz in traditional materials, i.e. microcracking normal to the maximum tensile direction maximize shielding, is not suitable for piezoelectric materials. This founding reveals that, besides the two sources of microcrack shielding discussed by Hutchinsion in traditional materials, there is another shielding source, i.e. the disturbance the near-tip electric field due to microcrack- ing. Moreover, J2-integral shows the path-independent nature when the integral contour encloses the microcrack completely. It has the same significance as the J1-integral during J-illtegral analysis for all the cracks.