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本文取不同试样由同一初始裂纹长度口a_0扩展到指定裂纹长度a_1所经历的循环数N_(ij)常用对数x_(ij)=lgN_(ij)作为随机变量,用一组14块LC9铝合金CCT试样的da/dN试验结果,检验了指定a_l下的x_(ij)基本遵循正态分布。然后通过24个不同a_i所对应的x_(ij)的变异系数分析,给出了为测定在置信度γ下处处与母体平均曲线相对偏差小于δ的平均da/dN曲线所需要的最少试样数。由LC9及其它铝合金、中高强度钢的试验数据估计,当取γ=90%、δ=5%时,最少试样数约为3～4。
In this paper, we take the common logarithm x_ (ij) = lgN_ (ij), which is a common logarithm of the number of cycles that different samples extend from the same initial crack length a_0 to the specified crack length a_1, The results of da / dN test on the alloy CCT sample show that x_ (ij) under the specified a_l basically follows a normal distribution. The minimum number of samples needed to determine the averaged da / dN curve with a relative deviation from the maternal mean at δ less than δ at the confidence γ is then given by the analysis of the coefficient of variation of x_ (ij) for 24 different a_i . From the LC9 and other aluminum alloy, high-strength steel test data estimates, when taking γ = 90%, δ = 5%, the minimum number of samples is about 3 ~ 4.