FATIGUE CRACK-PROPAGATION OF SHORT CRACKS
FATIGUE CRACK-PROPAGATION OF SHORT CRACKS
复制标题
DOI：
10.1115/1.3443647
复制
发表时间：
1979-01-01
影响因子：
1.2
通讯作者：
TOPPER, TH
中科院分区：
文献类型：
--
作者：
ELHADDAD, MH;SMITH, KN;TOPPER, TH
以往的研究表明，门槛应力强度因子和疲劳裂纹扩展速率都依赖于裂纹尺寸。非常短的裂纹的平均增长率大大超过了传统的应力强度裂纹增长规律拟合长裂纹数据。弹性和弹塑性断裂力学的解决方案进行修改，预测这种行为的短裂纹引入一个有效的裂纹长度l0到解决方案的强度因子和J积分的分析方法。在很短的裂纹长度处的门槛应力接近材料的疲劳极限，因此，一旦知道门槛应力强度因子和疲劳极限，就可以得到l0的值。预测短裂纹裂纹扩展速率的长期l0的准确性被发现是独立的所施加的应变水平。它随材料的晶粒尺寸线性变化，并且可以在表面处被认为是表面晶粒由于缺乏约束而降低的流动阻力的量度。
Previous studies have shown that both threshold stress intensity factors and fatigue crack growth rates are dependent on crack size. The average growth rates for very short cracks considerably exceed those given by conventional stress intensity-crack growth laws fitted to long crack data. Elastic and elastic plastic fracture mechanics solutions are modified to predict this behavior of short cracks by introducing an effective crack length l0into the solutions for intensity factors and the J integral method of analysis. The threshold stress at a very short crack length approaches the fatigue limit of the material, and therefore the value of l0can be obtained once the threshold stress intensity factor and the fatigue limit are known. The accuracy of the term l0in predicting crack growth rates for short cracks is found to be independent of the applied strain level. It varies linearly with the grain size of the material and can be considered at the surface as a measure of the reduced flow resistance of surface grains due to their lack of constraint.