【摘要】 阐述了美国空军耐久性设计手册（第二版）所做的发展，并指出其中存在的两个问题，即确定裂纹扩展率参数Ｑ时未考虑裂纹萌生时间的重要作用和没有说明使用期裂纹扩展率标准差σｚ的确定方法．通过研究，改进了裂纹扩展率参数Ｑ的确定方法，补充了确定裂纹扩展率标准差σｚ的途径．并通过了实例验证．更多还原

【Abstract】 This thesis introduces the method developed by USAF durability design homdbook Ⅱ.There are two problems in it. One is that the important of time of crack initiation isn’t considered while calculating crack growth rate parameter Q. Another is that the determination of the standard deviation σz of crack growth rate is not given. In this researching. the method of calculating paprameter Q is improved and the approach of determining standard deviation σz is given. A last. the methods are tested by a practical example.更多还原