本文提出了确定K_(IC)的一种数学方法——有理函数渐近法,不做测K_(IC)的实验,而是利用疲劳裂纹扩展速率da/dN第三阶段数据,经过适当处理后用有理函数y=(A+Bx)/(C+Dx)进行固定端点的拟合;再根据此有理函数的渐近线与x轴的交点来确定K_(IC)值.用三种材料的实验数据进行了验证,结果表明,用有理函数渐近法确定K_(IC)的精度较高。 This paper presents a mathematical method to determine K_ (IC) - rational function asymptotic method, without testing K_ (IC) experiments, but the use of fatigue crack growth rate da / dN third stage data, after appropriate treatment Fitting the fixed endpoint with the rational function y = (A + Bx) / (C + Dx), and then determining the value of K_ (IC) based on the intersection of the asymptotic line of this rational function with the x axis. The experimental data are validated. The results show that the accuracy of K_ (IC) is determined by the asymptotic method of rational function.