Research On Some Problems About Numerical Simulation Of Pressure Equipment And Its Engineering Application

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.