机械系统模糊可靠性设计理论及其仿真研究

【作者】 吕汝金；

【导师】 黄建龙；

【作者基本信息】 兰州理工大学 ， 机械制造及自动化， 2005， 硕士

【摘要】 随着对常规可靠性理论研究的深入,人们发现工程设计中不仅有随机性问题,还存在大量的模糊性问题,为了处理设计中存在的模糊性,就必须拓展常规可靠性设计理论。 把模糊数学和可靠性理论相结合的模糊可靠性设计可为解决设计中“模糊性”的一种好方法。 针对基本变量和状态变量的不确定性,既有随机性又有模糊性的情况,根据实际情况本文作如下处理: 1.在满足工程精度的范围内,可将它们视为确定性和随机性量来处理; 2.当存在大量的、不可避免的模糊信息时,用模糊方法处理不确定性因素; 3.对于很难直接利用模糊事件概率的计算公式获得模糊事件失效概率的,给出了将其转化为常规可靠性设计问题求解的方法; 4.对于转化为常规可靠性设计后仍不能获得其解析解的,本文探讨运用MATLAB软件进行模拟仿真来获得可靠性指标。 经过对三种模拟方法进行分析比较分析可以得出如下结论: 1.用MATLAB软件仿真能够满足工程精度要求; 2.三种方法所得结果虽有差异,但相对规律不变; 3.当模糊强度变量的形状参数较小且随机应力的标准差较大时,三种方法的结果非常接近; 4.三种模拟方法均可适用于工程应用,其中methodl最保守,可以根据实际情况需要选择相应的算法。更多还原

【Abstract】 With the study in the theory of general reliability, we found that there were not only random variables but also lots of fuzzy variables. We must widen the field of general reliability design.The fuzzy reliability design of which include fuzzy mathematics and reliability theory is a very well means that can deal with "fuzzy" of reliability design.In some extend, based on the randomness and fuzziness of basic variables and state variables, we can do it as follows in the paper:1. In the field of engineering intensive, we can regard them as general and random variables;2. The fuzzy method should be used when we faced to lots of and inevitable fuzzy information;3. By means of the transformation from fuzzy reliability design into general reliability design to deal with the problem which is very difficult to obtain the fuzzy events failure probability by the fuzzy events probability formulae directly.4. When we still can’t obtain the results, in the paper, we use the software " MATLAB " to simulate it, then get the reliabilities.Comparison and analysis in the illustrations, the results as follow:1. The simulating results of "MATLAB" can do for the engineering intensive;2. Three methods have different results, but the rhythm no change;3. When the shape parameter of fuzzy strength variable is small and the standard error of random stress is large, the results of three methods access to each other;4. Methodl is more suitable for engineering application than the existed methods in the references, we can select different means according to our need.更多还原