次表面微裂纹对偏折主裂纹扩展行为的分布位错理论研究

Theoretical Study on the Effect of Distributions of Dislocations of SubsurfaceMicrocracks on the Growth Behavior of Deflected Main Cracks

为研究在拉伸载荷作用下包含一条埋置偏折裂纹和一条任意位置微裂纹的半无限大平面问题.论文基于连续分布位错法,建立相应的位错密度积分方程,并采用GAUESS-CHEBSHEV数值积分法得到其力学参量.通过有限元法对理论结果进行了验证.埋置深度、微裂纹中心到主裂纹尖端的距离将对主裂纹尖端的应力强度因子产生影响;结果表明相比于无微裂纹的情况,在某些方位处微裂纹对主裂纹尖端的扩展起到促进作用,而在其他方位的微裂纹对主裂纹尖端的扩展起到抑制作用;主裂纹尖端的扩展方向和等效应力强度因子相比于倾斜微裂纹而言受水平微裂纹的影响更大.

To study the problem of a semi-infinite plane with an embedded deflected crack and a microcrack at any position under tensile loading,the integral equation for the corresponding dislocation density is established based on the method of continuous distributions of dislocations,and its mechanical parameters are obtained using the Gauss-Chebyshev numerical integration method.The theoretical results are verified using the finite element method.Compared with the case without microcracks,microcracks in certain directions(i.e.,the azimuth angle of the microcrack is between-90°and 45°)promote the growth of the main crack,while microcracks in other directions(i.e.,the azimuth angle of the microcrack is between 45°and 90°)inhibit its growth.The stress intensity factor at the main crack tip decreases with the increase of the embedded depth of the crack and the distance from the center of the microcrack to the tip of the deflected main crack.When the azimuth angle of the microcrack is between-90°and-65°,or between-25°and 10°,the propagation direction of the main crack deflects clockwise from the original propagation direction.When the azimuth angle of the microcrack is between-65°and-25°,or between 10°and 90°,the propagation direction of the main crack deflects counterclockwise from the original propagation direction.Horizontal microcracks have a greater influence on the propagation direction of the main crack and the equivalent stress intensity factor compared with inclined microcracks.