多种可靠度计算方法

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摘要

压力容器作为一种重要设备广泛应用于工程领域，其安全性和可靠性是现在研究的重要课题。压力容器在生产和使用过程中存在各种不确定性因素，如构件、缺陷尺寸参数的不确定性，工况载荷的随机波动，材料机械性能的随机性。本文将这些不确定性参数当作随机变量，考虑其概率分布形式，采用应力强度-干涉模型，利用一次二阶矩法，蒙特卡洛法和随机有限元法等可靠度计算方法对容器结构进行了可靠性分析，并讨论了各随机变量对可靠度结果的灵敏度。

本文对无缺陷压力容器的安全评定采用弹性失效判据，利用四种不同的方法计算了圆筒形和球形压力容器的可靠度，分析比较了各方法的优缺点。对于含凹坑缺陷的压力容器，文中采用基于塑性极限的塑性失效准则，其中极限荷载采用弹塑性增量法得到，通过ANSYS 软件批处理操作模拟蒙特卡洛法实现可靠性分析，并对GB/T 19624-2004《含缺陷压力容器安全评定》规范中的极限载荷安全系数进行了评估。本文最后对 GB/T 19624-2004《含缺陷压力容器安全评定》规范中给出的含凹坑缺陷压力容器安全评定方法做出了改进，提出了基于分项安全系数的含凹坑缺陷压力容器的安全评定方法。

关键字：压力容器；可靠性；应力强度-干涉模型；分项安全系数

Abstract

Pressure vessels as important equipments are widely used in engineering field. The research and study of their safety and reliability are the important issues now. Pressure vessels contain all kinds of uncertainty factors in the process and use of productions, such as uncertainty of the parameters in component and defect size, random fluctuation of the working loads and the randomness of the material mechanical properties. In this paper, these uncertain parameters are considered as random variables meeting specific probability distribution form. By a second-order moment method, Monte-Carlo method and random finite element method the reliability of pressure vessels is studied in the stress-strength interference model. And the sensitivity of the reliability of result to the various random variables is also discussed.

In this paper, the safety evaluation of pressure vessels without defect is based on the elastic failure criterion. Four different methods are used to calculate the reliability of cylindrical and spherical pressure vessels, and the advantages and disadvantages of each method are also compared. The plastic failure criterion based on plastic limit is applied to the safety evaluation of pressure vessels containing pit defects. In this study, limit load is calculated by the elastoplastic incremental method. Simulation of Monte-Carlo method to the reliability analysis is realized by ANSYS software batch operation. According to the result, the ultimate load of the safety factor in GB/T 19624-2004 "safety assessment of pressure vessels containing defects" is also evaluated. In the end of the article, the method of safety assessment of pressure vessels containing pit defect based on the GB/T 19624-2004 "safety assessment of pressure vessels containing defects" is improved by adopting subentry safety coefficient.

Key words: Pressure vessel；reliability；stress-strength interference model；subentry safety factor