Crack propagation tests were conducted with CCT specimens made by 2024-T3 Aluminum alloy in benign and corrosive environments to investigate the stochastic characteristics of crack growth. A random variable probability crack growth model, base on the modified form of Paris law, was used to characterize the stochastic performance. Distribution significance test has been done, which shows that the random variable X can be considered reasonably to follow log-normal distribution in all the 4 kind of environments. Variance analysis indicates that the scatter in wet air is greater than that in laboratory air significantly. Expressions for the probability distribution of crack size at any given loading cycle and the probability distribution of the random fatigue life at which a given crack size is reached were discussed. The corresponding calculations for the crack length distribution and P-a-N curves with certain reliability were carried out. The comparisons with experimental data indicate the validity of the proposed method.

进行2024-T3铝合金标准中心裂纹拉伸试件4种典型环境下的裂纹扩展试验,以试验数据为基础,通过对一般环境下的裂纹扩展模型进行修正,建立腐蚀环境下的裂纹扩展模型。对试验结果的分析处理表明,该模型能够很好描述各种典型腐蚀环境下裂纹稳定扩展阶段的裂纹扩展速率,能够较准确估算裂纹扩展寿命,腐蚀修正系数清楚地反映腐蚀影响的程度。通过对单一介质环境腐蚀修正系数的加权组合,模型可以推广应用于复杂环境下裂纹扩展分析。该模型便于充分利用现有材料裂纹扩展性能的数据。

提出了试验测定结构件细节疲劳额定值(DFR)的升降法方法，可以充分估计并节约总试验时间。通过数值模拟比较了升降法数据处理的半子样极大似然法和马尔可夫方法。为满足可靠度要求，对半子样极大似然法估计的疲劳强度标准差进行了修正，并给出了保证95%可靠度的疲劳强度的置信度要求的最少试件数。最后给出了升降法确定DFR的表达式。

将腐蚀对结构件疲劳寿命的影响当量转化为对细节疲劳额定值DFR的影响，建立了腐蚀条件下疲劳分析的DFR方法。 通过对标准S-N曲线方程的变换，得到了DFR的腐蚀当量折算系数与腐蚀对疲劳寿命的影响系数之间的关系，并研究了其中的参数对当量折算系数的精度的影响，从而给出了由疲劳试验确定当量折算系数的方法。基于地面停放预腐蚀和空中飞行腐蚀疲劳对疲劳寿命的影响相互独立的假设，得出了当量折算系数对预腐蚀和腐蚀疲劳的分解方法。

The influence of environmental corrosion on fatigue life of 2024-T3 aluminum alloy is investigated in this paper. Experiments with center-hole specimens and CC (T) specimens are conducted and reported. The test result shows that the corrosion influence is becoming serious while the environmental causticity is increasing, and the influence on crack initiation life is greater than that on crack propagation life. Analysis of the test data also indicates that the environmental causticity enlarges the dispersivity of fatigue life. Using the corrosion-modification-factor obtained by eigenvalue or mean value to prediction the fatigue life with high reliability will cause an unconservative conclusion.