3-D Finite Element Analysis of Egg-Shaped Digester and Reliability Analysis Based on Probability Density Evolution Method

摘要

In the recent years, the construction of the sewage treatment plant has increased day by day and the capacity of the construction of sewage treatment has increased too. So adopting reasonable, economical, reliable digester seems very important.The egg-shaped digester is large-scale shell structure whose thickness of cross section always changes and the fluid-solid interface of the pre-stressed egg-shaped digester is curve. When the digester is vibrating, fluid will slosh following with vibration of the digester. Fluid Sloshing exerts an influence to the vibration of digester on the contrary. So it is comparatively complicated for calculation of internal force. There are two kinds of the simplified finite element method in documents, but they can not meet the demand of precision. So the more accurate method is using the three-dimensional finite element to analyze the egg-shaped digester in fact. This paper uses ANSYS finite element software to consider fluid-solid coupling vibration and calculates static response, modal analysis and time-history dynamic analysis for the egg-shaped digester. In fact, not only the load but also the physical parameters of the structure are uncertain during using period of the structure. When analyzing service reliability of structure, it is necessary to consider the physical parameters of structure and random characteristics of load simultaneously. The stochastic structural analysis becomes the foundation of service reliability analysis of the structure. In the research in recent years, one probability density evolution method of the stochastic structural response develops. Through this method, the family of curve of probability density evolution of the structural response quantificationally is provided accurately Therefore according to appointed response limits of displacement, it can calculate and provide the reliability of stochastic structure at random loading directly. After introducing the probability density evolution method briefly, the paper gives the analysis method based on density evolution and considers the dynamic reliability analysis of the physical parameters of the egg-shaped digester.