【作者】 路智敏；

【导师】 李强；

【作者基本信息】 北京交通大学 ， 车辆工程， 2009， 博士

【摘要】 安全性与经济性的统一是压力容器设计的基本要求,按现行的国内外设计规范,无论是常规设计还是分析设计仍然以传统的安全系数法为主,把各种参数,如材料的强度、零部件的尺寸、所受的载荷等视为确定量,忽略了多种引起上述参数发生变化的随机因素,参数的取值往往偏于保守,使所设计的压力容器及零部件的结构尺寸偏大、不经济。研究表明:高的安全系数和高的结构可靠度并不一定是等价的。另外,确定性设计方法对不同重要程度的压力容器均采用了相同的安全系数,是不合理的。随着原材料制造技术、过程装备制造水平及使用过程控制手段的提高,在压力容器的设计、制造和使用过程中,以材料的力学性能参数、壳体的几何参数等为随机变量的压力容器的可靠性设计将发挥重要的作用。因此,将可靠性设计概念应用于压力容器设计中,具有非常重要的工程意义和学术价值。论文根据上述背景,对压力容器中各种典型的回转形壳体的可靠度计算公式进行了推导,利用随机有限元方法对压力容器不连续结构进行了可靠性计算,同时将可靠性设计方法应用于固体火箭发动机壳体。论文主要进行了以下几个方面的工作:1.根据圆柱形筒体的不同失效形式以及同一失效形式下的不同强度理论,利用可靠性设计中的二阶矩法推导出相应的可靠度表达式,并将其应用于同一算例当中。通过算例比较常规设计与可靠性设计以及不同可靠性设计公式计算结果的差异,给出了圆柱形筒体可靠性设计公式选择的建议。2.基于无力矩理论及弹性失效设计准则中的第一强度理论,利用可靠性设计中的二阶矩法分别推导出球形壳体、椭球形封头、碟形封头及锥形壳体的可靠度表达式。基于平板应力分析,利用二阶矩法分别推导了各种形状平盖的可靠度表达式。3.在理论分析的基础上,提出采用随机有限元的方法求解压力容器结构不连续部位的可靠度的方法及其注意事项。并且将其应用于高压容器筒体与封头的连接部位,对这一结构实行了参数化建模,在确定性有限元分析的基础上进行了随机有限元分析,不仅求出其可靠度,而且还对其输出变量的最大节点等效应力(maxstr)和输出功能函数(Z)的灵敏度进行了分析。4.对某型号的金属制固体火箭发动机壳体的圆柱形筒体和椭球形封头,采用基于弹性失效设计准则的最大主应力理论推导出的圆柱形筒体和椭球形封头的可靠度计算公式求出其可靠度,利用有限元软件对该壳体的不连续部位进行了随机有限元分析,不仅求出其可靠度,并对不连续部位的输出变量的最大节点等效应力(maxstr)和输出功能函数(Z)的灵敏度进行了分析,为结构的优化设计提供了理论依据。5.制备了8个碳纤维缠绕复合材料压力容器试样,通过试验获得了壳体的纤维强度、缠绕角、几何尺寸、爆破压强等随机变量特征值,作为算例中的已知参量;基于薄膜理论和网格理论推导了纤维缠绕复合材料压力容器可靠性安全系数表达式,求出算例中壳体纤维层的总厚度,并分析了各参量变异系数对壳体爆破压强分散程度的影响。为复合材料压力容器可靠性设计提供了理论依据。更多还原

【Abstract】 The basic needs of pressure vessel design is safety and economic. The safe is premise and the economy is aim. The aim of economy may be meeted in the premise of safe. At present, according to the international norm of pressure vessel design the safe coefficient method is main current in either the normal design or the analysis design. Various parameters such as strength of material, size of parts, and loads have been regarded as fixed parameters in the norm. The random changes of the parameters are ignored with the change of various condition and the values of parameters are conservatively selected. So that the sizes of the pressure vessels and the parts designed are larger and the design is not economic. Frequent accidents showed that high safe coefficient and high reliability are not same. Besides, fixed design methods have been using same safety factors for different important pressure vessels. So the conventional fixed design methods are not reasonable. With improving manufacturing technologies of row materials and process equipments as well as controlling methods of using process equipments, reliability design of pressure vessels which regards strength of material, size of parts, and loads as random variables will plays an important role in using pressure vessels. So pressure vessel design using reliability concept is very important.According to the above conditions the reliability calculation formulas of various shells of revolution were conducted in the dissertation. The reliability of the uncontinuous structure of pressure vessels were calculated by Random finite element analysis. And the method was applied to reliability design of solid rocket motor vessel. The main contents are as follows,1. The reliability formulas of cylindrical shells with internal pressure based on the various failure norm as well as various strength theories of same failure norm were conducted by the second moment method. Then they were applied to an engineering case. The reliability design of cylinder vessels with internal pressure was compared with the rule design. And difference of various reliability formulas of cylinder vessels was found. At last selecting reliability formulas regularity vas proposed.2. The reliability formula of spherical shells, and ellipsoidal heads, and dished heads, and conical shells based on the non-moment theory were conducted by using the second moment method. The reliability formula of various based on the plate theory were conducted by using the second moment method.3. The model of an uncontinuous structure of pressure vessel was created by parameter mode of ANSYS software and analyzed by random finite element analysis. Not only the reliability of the structure was calculated, but also the sensitivity of the maximum stress (Von Mises SEQV) and the performance function were analyzed.4. The solid rocket motor metal vessel was analyzed by random finite element. Not only the reliability of the vessel was calculated, but also the sensitivity of the maximum stress (Von Mises SEQV) and the performance function were analyzed in order to provide a reference for optimization design of the structure.5. The reliability safe coefficient of Carbon Fiber Reinforced Plastics solid rocket motor vessel based on the non-moment theory and the net theory was conducted. Eight carbon fiber reinforced plastics (CFRP) pressure vessels were manufactured and the experiments were conducted to obtain the probabilistic distribution of design variables, such as the fiber strength, winding angle, geometric size, burst strength and so on. The fiber thickness was calculated by using the reliability safe coefficient formula.更多还原