介绍了金属结构材料断口定量分析疲劳寿命模型,即Paris公式、梯形法及断口宏观特征模型的应用条件和范围;利用Paris公式和梯形法对7B04铝合金和TA15钛合金疲劳试样断口进行疲劳扩展寿命定量分析,通过对两种方法计算结果的比较,并结合梯形法的本质,提出了对梯形法修正的前提和具体修正方法,即当裂纹开始扩展尺寸(a0)大于第一个测量点的裂纹长度(a1)或a0与a1非常接近时,可不对梯形法进行修正,当a0小于a1时,则计算疲劳扩展寿命时需对梯形法进行修正,此时梯形法公式中不除2;第一个测量点值后的算法保持不变;用修正后的梯形法计算的疲劳扩展寿命表明了修正方法的合理性.

In this paper,the quantitative fractography analysis model and means of metal structure materials are introduced,including the Paris formula,the trapezium method and the models based macroscopic characteristics of fracture surface.The using precondition of every model is also introduced.The fatigue expanding life of the fracture surface of 7B04 aluminum alloy and TA15 titanium alloy was calculated using Paris formula and trapezium method.The calculating results were compared and analyzed.Combing with the essence of trapezium method,the precondition and improving measure of trapezium method were proposed.When the beginning expanding crack size (a0) is more than the crack length of the first measurement station (a1),or the a1 is nearby the a0,the trapezium method is not necessary to be modified,but when a0 is shorter than a1,the trapezium method is needed to be modified during calculating the fatigue life between a0 and a1,i.e.,the trapezium method formula does not need to be divided by 2.The trapezium method formula keeps its primary form when calculating the life after a1.The calculating results using improved trapezium method show that the improved measure is reasonable.