中文摘要：

以7049-UA铝合金为研究对象，用弹塑性有限元方法分析拉压循环载荷下，三条不同裂纹长度的裂尖应力场，通过裂尖的应力状态定义一个考虑压载荷影响的有效应力强度因子范围参数AKeff’，并利用此参数，定量分析循环拉压载荷对铝合金疲劳裂纹扩展的促进作用，并提出一种简便的利用有限元方法拟合应力比为负值时Pails区的疲劳裂纹扩展速率的方法，与已发表的实验数据相比较，得到较好的验证。

英文摘要：

An elastic-plastic finite element analysis has been performed to solve the crack tip stress fields for three different crack lengths under tensile-compressive loading in 7049-UA Aluminum alloy. A redefined effective stress intensity factor range, AKeff＇, incorporating the effect of the compressive stress, based on the finite element analysis results of the crack tip stress state, is proposed. Using this new parameter, the influence of the negative stress on the fatigue crack propagation rate under the cyclic tension-compression loading can be revalued quantitatively. A simple finite element method is introduced to predict the fatigue crack propagation rate under the negative stress ratio. The finite element calculated results has been used to correlate the published experimental data and good correlation has been obtained.