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为了对手册的出版提供资料,目前,对铝锻造合金的断口疲劳性正进行长期研究。这些合金都是高强度AlZnMgCu(7000系)合金,最初,只考虑了恒振幅疲劳负载。通常,把应力振幅Sa与疲劳寿命的对数N之间的关系作成与数据拟合的所谓S—N曲线,来表示恒振幅疲劳试验的结果。作S—N曲线的常用方法是凭视力判断通过各数据点的平滑曲线的最佳位置,徒手画出曲线。这种方法显然很主观,而且当数据明显分散和接近疲劳极限时,这种方法还值得怀疑。接近疲劳极限时,必然会有已断裂和未断裂这两种试样,它们在疲劳寿命上相差很大。
In order to provide information on the publication of the handbook, at present, long-term research is being conducted on the fracture fatigue of aluminum forged alloys. All of these alloys are high-strength AlZnMgCu (7000 series) alloys. Originally, only constant-amplitude fatigue loading was considered. Normally, the relationship between the stress amplitude Sa and the logarithm N of the fatigue life is made as a so-called S-N curve fitted to the data to show the result of the constant amplitude fatigue test. The usual method for making S-N curves is to determine the best position of the smooth curve through each data point by visual acuity. This approach is obviously very subjective, and it is questionable when the data is significantly distorted and approaches the fatigue limit. Near the fatigue limit, there will inevitably be two samples that have been fractured and not fractured, and they differ greatly in fatigue life.