悬臂弯曲加载表面裂纹扩展长度与深度的关系研究

Study on Relationship Between Length and Depth of Surface Crack Propagation under Cantilever Bend Loading

本文根据10CrNiMo高强钢的材料常数C、m,按照Cycle by Cycle方法的计算流程,采用Newman-Raju公式和Paris公式,分别计算了悬臂弯曲加载方式下表面裂纹扩展沿长度和深度方向上的应力强度因子范围△K,得到了裂纹扩展长度与深度的关系及其裂纹扩展速率。通过与试验结果的对比,分析了理论计算可能出现的误差,并对Newman-Raju公式进行了修正。结果表明,公式计算所得表面裂纹扩展趋势和裂纹扩展速率趋势与试验结果是一致的,且修正后的Newman-Raju公式在裂纹扩展形貌和扩展速率方面与试验数据拟合曲线都可以较好吻合。采用修正后的Newman-Raju公式,还可以很好地对具有不同初始裂纹形状试样的表面裂纹扩展情况进行预测。

According to Cycle by Cycle calculation procedures,the range of stress intensity ΔK along the length and depth direction of surface cracks under cantilever bend loading respectively to build the relationship between crack length and depth,and the crack growth rate was calculated by using the material constant C,m of 10 CrNiMo high strength steel and the Newman-Raju formula and Paris formula. The possible error of theory calculated value was analyzed and Newman-Raju formula was modified.The results showed that the trend of surface crack growth and crack growth rate calculated were consistent with the test results. the modified Newman-Raju formula could agree well with the experimental data fitting curve both in crack growth shape and growth rate. Simultaneously,surface crack growth could be well forecasted with different initial crack shape of sample using the modified Newman-Raju formula.