p-S-N曲线试验方案设计与验证

发布时间：2018-05-15 22:39

本文选题：p-S-N曲线 + 成组法　；参考：《东北大学》2011年硕士论文

【摘要】：考虑到疲劳试验数据的分散性,将疲劳寿命与一定的可靠度联系起来,从而可以得到一组不同可靠度p下的S-N曲线,即可靠度-应力-疲劳寿命曲线,称之为p-S-N曲线。p-S-N曲线广泛应用于表征材料和零件疲劳性能,故又称为概率疲劳性能曲线。对于承受交变载荷的材料而言,该曲线是一种十分重要的基础设计资料,它代表了更客观、更完整的应力-寿命关系。成组法是当前通用的p-S-N曲线标准测试方法,该方法充分考虑到了试样疲劳强度数据的随机性和分散性,在试验中使用较多的试样。成组法试验结果能满足一定的统计要求,较真实地反映母体的特征,试验精度与置信度均较高。但是,由于成组法需要的试样较多,从而直接导致试验所需时间长,工作量大,费用高。针对传统成组法的缺点,国内外学者运用经典的疲劳理论和数理统计工具,提出了一些高效或简化的试验方法,以减少试验工作量。这类方法中,有的是建立在单点法得出的中值S-N曲线基础之上,有的试验的样品数量太少,使所得结果的准确性和置信度下降,难以满足工程的要求。本文运用性能-寿命概率映射原理,认为材料性能处于其母体分布某一概率分位点的试样,在任何应力水平下的寿命都将处于对应于该水平的寿命母体分布的同一概率分位点上。因而,不同应力水平下的寿命分布存在映射关系,不同应力水平下的各寿命样本点之间存在一一对应关系。根据这个对应关系,就可以把不同应力水平下的寿命试验数据转换到某一个指定的应力水平上,形成样本聚集和信息融合效应,进而进行寿命分布参数估计。本文设计了基于性能-寿命概率映射原理的小样本p-S-N曲线试验方案,即新型小子样法。该方法基于疲劳寿命服从对数正态分布,且对数寿命均值和标准差均与应力水平呈线性关系的假设,以及方差统计检验原理,最终能够用较少的试样试验得出置信度较高的p-S-N曲线。
[Abstract]:Considering the dispersion of fatigue test data, a set of S-N curves under different reliability p can be obtained by associating fatigue life with certain reliability, that is, the reliability-stress-fatigue life curve. It is called p-S-N curve. P-S-N curve is widely used to characterize the fatigue properties of materials and parts, so it is also called probabilistic fatigue performance curve. For materials subjected to alternating load, the curve is a very important basic design data, which represents a more objective and complete stress-life relationship. Group method is a common standard test method for p-S-N curves. This method takes full account of the randomness and dispersion of fatigue strength data of samples and is used more frequently in the test. The results of the group test can meet certain statistical requirements and reflect the characteristics of the parent body more truthfully. The precision and confidence of the test are both high. However, due to the large number of samples needed by the group method, the test time is long, the workload is large and the cost is high. Aiming at the shortcomings of the traditional group method, the domestic and foreign scholars put forward some efficient or simplified test methods by using the classical fatigue theory and mathematical statistics tools, in order to reduce the test workload. Some of these methods are based on the median S-N curve obtained by the single point method, and some of the samples are too small to reduce the accuracy and confidence of the obtained results, which is difficult to meet the requirements of engineering. Based on the principle of performance-life probabilistic mapping, it is considered in this paper that the material's properties are at a probability locus of its parent body. The lifetime at any stress level will be at the same probability locus corresponding to the lifetime parent distribution at that level. Therefore, there is a mapping relationship between the life distribution at different stress levels and a one-to-one correspondence between the life sample points at different stress levels. According to the corresponding relation, the life test data under different stress levels can be converted to a certain stress level, and the effect of sample aggregation and information fusion can be formed, and then the life distribution parameters can be estimated. In this paper, a small sample p-S-N curve test scheme based on the principle of performance-life probability mapping is designed, that is, a new small sample method. This method is based on the assumption that the fatigue life suit is distributed from logarithmic normal, and the logarithmic life mean and standard deviation are linearly related to the stress level, as well as the principle of variance statistical test. Finally, the p-S-N curve with higher confidence can be obtained with less sample test.
【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH140.7

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