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浙江大学学报(工学版)
J4  2009, Vol. 43 Issue (8): 1443-1447    DOI: 10.3785/j.issn.1008-973X.2009.
    
Relationship between stress distribution along slant crack and
opening displacement on crack-surface
 MA Wei-Li
College of Light Industry, Harbin University of Commerce, Harbin 150028, China
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Abstract  

The load is not always vertical to the crack in an actual mechanical part, so it is necessary to study the crack deformation behavior under the mixed-mode stress condition. It is difficult to measure the stress distribution along a crack for complex mechanical structures. Using the cracks with slant angle of 45° introduced by the cycle stress of mode I at zero stress ratio, this work measured the opening and sliding discontinuous displacements along the crack, then calculated the mode I and mode II stress distributions. Furthermore, finite element method (FEM) was used to simulate the dimensions of the specimen used in the experiment. The factors influencing the opening and sliding discontinuous displacement on the crack surface were discussed by comparing experimental and FEM data. The results show that the sliding deformation of fatigue crack is restrained because of the contact of crack zigzag surfaces especially at the crack tip. This effect is outstanding while the contact surface increases, which causes by the decreased opening deformation. On the contrary, the crack opening deformation increases because of the crack surface contact. And the opening deformation behavior is affected by the compressive residual stress near the crack.

Published: 28 September 2009
CLC:  TU 51  
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Cite this article:

MA Wei-Li. Relationship between stress distribution along slant crack and
opening displacement on crack-surface. J4, 2009, 43(8): 1443-1447.

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http://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2009.     OR     http://www.zjujournals.com/eng/Y2009/V43/I8/1443


倾斜裂纹的应力分布与裂纹面开口位移的关系

由于存在裂纹的机械结构的受力方向未必与裂纹方向相垂直,有必要研究裂纹在混合型应力条件下的应力分布及位移特性,而实际机械结构的形状往往很复杂,直接测得裂尖前沿的应力分布是很困难的.为此,在应力比为零的I型循环应力下制作倾斜角度为45°的裂纹,通过测量裂纹面的开口位移,计算得到了裂尖张开方向的应力分布和滑移方向的应力分布.对实验中试件和裂纹的实际尺寸进行了有限元模拟计算.通过比较实验和模拟计算结果,分析了在混合型应力条件下影响裂纹面开口位移特性的因素.结果表明,裂纹表面的凹凸不平导致的接触会影响裂纹面（特别是裂尖处）的滑移变形；当裂纹张开方向的变形较小时,随着裂纹表面接触面积增加,裂纹滑移方向的变形阻力增大,这种影响表现得更为突出；相反,裂纹表面接触对裂纹张开方向的变形却起到了促进的作用；另外,由于压缩残余应力的作用,疲劳裂纹的张开位移受到制约.

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