【作者】 苏文献；

【导师】 郑津洋；

【作者基本信息】 浙江大学 ， 化工过程机械， 2003， 博士

【摘要】 承压设备全寿命数值模拟是现代设计的发展方向，而强度数值模拟是其关键之一。现有的分析设计规范对承压设备力学响应数值解的评定未做十分明确的规定，在应力分类方法中，存在着有限元应力数值解如何合理分类的困难；在直接方法中，确定承压设备极限承载能力的各种方法有着较大的差别。因此，建立操作性强、概念清晰、减少人为因素干扰的承压设备强度数值模拟方法，对消除承压设备数值模拟的不确定性，有效地对承压设备强度进行评定，具有重要意义。本文在教育部高等学校博士学科点专项科研基金(资助号：20010335032)的资助下，开展了防止承压设备发生总体塑性变形与渐增塑性变形的强度数值模拟方法的研究工作，并应用于实际工程中，取得了如下的主要创新成果： 1．提出了按5％应变确定塑性载荷的最大主应变准则。该准则可以用来防止承压设备的总体塑性变形。 5％最大主应变准则只需要经过弹塑性分析，求出承压设备在载荷作用下产生的最大主应变，当最大主应变达到5％时，作用在承压设备上的载荷就是塑性载荷。与其它已有确定塑性载荷的准则相比较，5％最大主应变准则不需要预先画出载荷—变形(应变)曲线，因而，就不需要选择变形参数(选择变形点的位移，或者容器体积的变化等)。 5％最大主应变准则在商用有限元分析软件ANSYS上很容易实现，主应变是ANSYS软件标准的输出项，通过ANSYS的参数化设计语言(APDL)可以得到当承压设备中某一部位的最大主应变达到5％时的塑性载荷。 2．提出了一种通过构造最佳残余应力场确定下限安定载荷的方法。根据弹塑性分析求出结构在静载荷作用下的塑性载荷，然后，卸载产生一个残余的应力场，通过对残余应力场进行修正，使其处处不发生反向屈服，得到最佳残余应力场。将最大载荷作用下的线弹性应力场与最佳残余应力场迭加，确保迭加后的应力场处处不发生屈服，从而满足Melan静力安定定理的基本要求，就可以确定下限安定载荷，达到防止承压设备发生渐增塑性变形的目的。 利用构造最佳残余应力场求安定载荷的方法可以在现有的商业有限元软件敏浙江人学博1学位论文在有限次次零至安定载荷循环作用下弹塑性分析，验证在安定载荷作用下，承压设备没有发生渐增塑性变形。通过与其它求安定载荷方法及试验的比较说明，本文提出的计算方法能更好地利用材料的塑性，具有较高的工程应用价值。 3.对齿啮式快开压力容器通过接触单元来数值模拟齿的接触过程，建立了基于整体有限元应力分析塑性分析和应力分类与评定的齿啮式快开压力容器的基本方法，并开发了相应的有限元程序。在边界条件的处理上，摈弃了过去仅从平衡的角度处理接触边界条件，采用接触单元将接触问题引入齿啮式快开容器的有限元整体模型中。 应用本文提出的5%最大主应变准则，求得了硫化罐这样一种齿啮式快开压力容器的塑性载荷，并与其它方法求得的塑性载荷进行了分析比较。结果表明，应用5%最大主应变准则求得的塑性载荷与其它方法获得的塑性载荷相当吻合，但是，它比其它准则更容易实现。更多还原

【Abstract】 Numerical simulation of pressure vessel in its whole life is the developing aspect, while numerical simulation of strength is the key factor. The mechanical responses of pressure vessel under action are not prescribed clearly in many codes and standards of Design By Analysis(DBA) as far as the state-of-the-art. For finite element analysis utilizing solid models, implementation problems of the Stress Categorisation Route, where the calculated stress should be identified as membrane, bending or peak, become apparent. Some methods used to guard against gross and progressive plastic deformation have different on some extent in Inelastic Route. It is important to develop some methods of strength numerical simulation of pressure vessel, the advantage of these methods is easily to be used, have clear conception and good impersonality. So that, the strength of pressure vessel can be effectively assessed to avoid the uncredibility of the numerical simulation of pressure vessel. Supported by the Doctoral Training Foundation of Education Ministry of China, The research results are as follows:(1) A criterion of 5% maximum principal strain for plastic collapse is presented. 5% primacy principal strain indicates that gross plastic deformation occurs when a pressure vessel (of ductile material) has a value of 5% maximum principal strain at any point.The proposed criterion is used to evaluate plastic loads in pressure vessel design by analysis using elastic-plastic finite element analysis to guard gross plastic deformation of pressure vessel. Compared with existent criterion, the new criterion has several advantages: the definition of plastic load is not based on the curve of load versus deflection(or strain), and the choice of deformation parameter such as displacement of deflection point, volume change ,etc is not needed. The example analyses presented show that plastic load given by the 5% maximum principal criterion are comparable with given by the two elastic slope (TES) and the tangent intersection (TI) criteria. This indicates that the 5% maximum principal strain criterion is suitable method for characterizing gross plastic deformation.In practice, the criterion is simple to implement in a commercial finite element program such as ANSYS. ANSYS give principal strain as a standard result for solid element and a brief external ANSYS APDL macro is all that is required to implement the criterion.(2) According to Melan’s theorem, a method to construct an optimal self-equilibrating stress field is established. The linear-elastic stress field with the possible greatest value of internal pressure has to be determined, superposition with the optimal self-equilibrating stress field. The shakedown load of pressure vessel can be defined to guard progressive plastic deformation.The definition of shakedown load by constructing an optimal self- equilibrating stress field is implemented in a commercial finite element program such as ANSYS. A simulation with pressure cycling between 0 and shakedown pressure is shown that the model shakes down under this cyclic action after four action cycles, within thenumerical accuracy that can be expected. Compared with other methods and test, the present method can offer significant material savings, and is generally easier to apply in engineering.(3) The whole finite element model of tooth-locked quick-actuating closure pressure vessel is created by simulating the contact conduct between the teeth utilizing the contact element. The contact element is introduced in order to create whole FE model, such that a sound boundary condition is formed while the old one formed by equilibrium is eliminated.The plastic load of a sulfuration drum under internal pressure is defined by the 5% maximum principal strain criterion. The plastic load given by this criterion is comparable with those given by the TES and TI criteria as well as the Stress Categorisation Route, but the new criterion is generally easier to implement in a commercial finite element program.更多还原