有效应力强度因子幅值计算模型的验证

Validation of an effective stress intensity factor calculation model

裂纹闭合效应在金属疲劳中有着十分重要的作用,裂纹闭合概念已经用于解释变幅载荷作用下的裂纹扩展问题,已提出了许多基于裂纹闭合概念的有效应力强度因子计算模型。黄等人在Newm an模型的基础上,提出了考虑因素更全面且便于应用的有效应力强度因子幅计算模型以及变幅载荷下工程结构疲劳寿命预测模型。为了验证该模型对不同材料的有效性和适应性,收集了一些相关的试验数据,和该模型的预测结果对比发现该模型的预测结果和试验数据符合得很好。对几种钢、铝合金和钛合金材料在不同应力比下的裂纹扩展速率数据用该模型转换成用有效应力强度因子表示的裂纹扩展速率,结果表明由有效应力强度因子幅表示的扩展速率将不同应力比下较分散的裂纹扩展率数据集中在一个很小的分散带内,同时得到了有参考价值的的一些结论。

Crack closure effect is important for metal fatigue.Crack closure was used to describe the crack growth under variable amplitude loading. Many effective stress intensity factor calculation models based on the crack closure concept were reported.Huang et al proposed a unified effective stress intensity factor range calculation equation based on the Newman＇s mode and fatigue crack growth life calculation model of engineering structures subjected to variable amplitude fluctuation loads.Some experimental data of crack opening ratio and crack growth rates of different material under different stress ratios were collected to validate this model. The predicted values by the model are compared with the test data.The comparisons show that the predicted values are in good agreement with the experimental data. Furthermore,these crack growth rate data of titanium alloy, aluminum alloy and steel under different stress ratios were expressed vs effective stress intensity factor range by the model.The results show that these crack growth data of each material under different stress ratios are in a narrow scatter band using the newly defined effective stress intensity factor range. Meanwhile, some useful conclusions were drawn.