随机疲劳裂纹扩展新模型

疲劳裂纹扩展的随机特性是工程结构可靠性分析和制定检查、维修计划野性 须考虑的因素，提出疲劳裂纹随机扩展模型，不仅考虑了时间参数影响，而且还考虑了初始裂纹尺寸分布影响。模型适应范围广，由于采用了一次二阶矩近似方法简化随机过程计算，便于工程应用。

A SIMPLE STOCHASTIC CRACK GROWTH ANALYSIS METHOD

Form a macroscopic viewpoint, it is often convenient to regard a metallic material as a homogeneous continuum. However, the scatter generally observed in fatigue testing of a metallic material arises precisely because it is no longer regarded as a homogeneous continuum on a microscopic scale. In addition to the stochastic nature of the crack growth process, practical identical specimens in replicate tests exhibit dispersion in geometry, material properties, thus the stochastic nature of the phenomena is enhanced. The stochastic nature of the fatigue crack growth phenomena should be considered in practical engineering failure analysis. The prediction of stochastic crack growth accumulation is important for the reliability analysis of structures as well as the scheduling of inspection and repair/replacement maintenance. Based on the log-normal random process model and a second order approximation, a new simple stochastic crack growth analysis method is presented for practical applications. In addition to taking into account the correlation parameter, the loading randomization and the initial flaw size distribution are accounted. Hence, it is flexible enough to cover a wide range of dispersion of the crack growth accumulation. The analysis method can be implemented easily by using both deterministic and statistical crack growth behaviors. Based on the same ideas proposed in this paper, a three-parameter Weiboll distribution can also be adopted to reflect the influences of skewness of the probability density function. So more random variables might be concerned with in reliability analysis.