改进疲劳损伤模型与基于P-S-N的疲劳可靠性研究

发布时间：2018-05-25 09:32

本文选题：虚拟载荷谱 + 疲劳损伤　；参考：《湖南大学》2014年硕士论文

【摘要】：疲劳损伤模型是疲劳寿命计算的理论基础，，Miner准则是疲劳寿命计算中典型应用的损伤模型，然而由于其存在假设以及计算公式中的经验数据，使得计算结果与工程实际存在着偏离，在工程应用中存在安全隐患。本文在目前现有的Miner疲劳损伤准则和常规可靠性设计的基础上，考虑到疲劳加载顺序对疲劳损伤裂纹的影响，提出一种基于虚拟载荷谱加载区间长度等分的计算模型，进行疲劳寿命预测，利用小样本实验数据对P S N曲线进行拟合，分析研究基于P-Sa-Sm-N曲面疲劳可靠性。主要研究工作及创新点体现在以下方面： 1)提出一种基于虚拟载荷谱加载区间长度等分的数学模型，用于疲劳损伤寿命的计算预测。在传统Miner准则基础上，将疲劳载荷谱的加载工作应力区间进行虚拟的等分，建立一种改进的疲劳损伤模型，从理论层面证明其疲劳寿命的收敛性。应用于钢板弹簧的疲劳寿命预测，验证了模型的有效性。 2)P-S-N曲线的公式拟合。采用线性回归技术求解方法，将三参数模型、Langer模型和Basquin三种常用应力-寿命模型的P-S-N曲线表示为对数疲劳寿命均值和均方差线的广义形式，并对三种模型的拟合结果进行对比分析。45碳钢试样对称循环加载成组法疲劳试验结果分析说明了方法的有效性。 3)基于P-S-N曲线，对疲劳可靠性计算结果的准确性与影响因素进行研究。在可靠度-应力-寿命基本理论基础上，研究了P-Sa-Sm-N曲面的构建方法和基于P-Sa-Sm-N曲面的疲劳可靠性，考虑到疲劳加载工作应力与强度参数的不确定性，详细分析了最大应力和最小应力的取值、应力循环比、强度变差系数和应力变差系数等选取不同参数值时对疲劳可靠性的影响。本疲劳损伤模型的提出为疲劳损伤模型的合理完善提供了一种新的思路，可以节约疲劳试验的成本和时间。疲劳可靠性的研究成果可以应用于产品开发设计，具有工程应用前景。
[Abstract]:The fatigue damage model is the theoretical basis of fatigue life calculation, and Miner criterion is a typical damage model in fatigue life calculation. However, due to its existence hypothesis and the empirical data in the calculation formula, the calculation result is deviated from the engineering practice, and there is a hidden danger in the engineering application. This paper is in the present Miner On the basis of fatigue damage criterion and conventional reliability design, taking into account the effect of fatigue loading sequence on fatigue damage cracks, a calculation model based on the interval length of load spectrum loading is proposed, and the fatigue life prediction is carried out. The P S N curve is fitted with small sample data, and the analysis and research based on the P-Sa-Sm-N surface Fatigue reliability.
The main research work and innovations are reflected in the following aspects:
1) a mathematical model based on the length of the loading interval of the virtual load spectrum is proposed, which is used to predict the fatigue life. On the basis of the traditional Miner criterion, the stress interval of the fatigue load spectrum is equally divided, and an improved fatigue damage model is established, which proves the convergence of the fatigue life from the theoretical level. It is applied to the fatigue life prediction of leaf springs, and the validity of the model is verified.
2) the formula fitting of the P-S-N curve. By using the linear regression technique, the three parameter model, the Langer model and the three common stress life model of Basquin are expressed as the generalized form of the mean and the mean variance line of the logarithmic fatigue life, and the comparison and analysis of the fitting results of the three models are compared and analyzed in the symmetric cycle of the.45 carbon steel sample. The fatigue test results of loading group method show the effectiveness of the method.
3) based on the P-S-N curve, the accuracy and influence factors of the fatigue reliability calculation results are studied. On the basis of the basic theory of Reliability stress life, the construction method of P-Sa-Sm-N surface and the fatigue reliability based on the P-Sa-Sm-N surface are studied, and the uncertainty of the stress and strength parameters of the fatigue loading work is taken into account, and the detailed analysis is made. The influence of maximum stress and minimum stress, stress cycle ratio, intensity variation coefficient and stress variation coefficient on fatigue reliability is discussed.
The proposed fatigue damage model provides a new idea for the rational improvement of the fatigue damage model, which can save the cost and time of fatigue test. The research results of fatigue reliability can be applied to the design of product development and have the prospect of engineering application.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB114.3

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