Stress Analysis Of The Reducer Of Directly Buried Based On The Finite Element

With the continuous development and improvement of the technology of directly buried,the scale of central heating expands gradually,directly buried heating pipe has become a major hub for the heating system.Reducer is the dangerous pipe segment which is accident-prone.Doing comprehensive stress analysis for reducer,obtain accurate calculation of the stress and displacement is conducive to enhancing heating pipes system reliability and help to improve the security of the entire heating system,save the investment.The stress analysis of reducer which belong to directly buried heating system can Dialectically reference and absorption research results of machinery,petrochemical and other fields.But the conditions which the reducer belongs to exist certain differences in above fields with the directly buried heating fields.So the stress analysis of reducer in machinery,petrochemical and other fields is not fully applicable to the field of directly buried heating.Though the technical experts have been researchen and analysised the stress of the directly buried reducer,but not through the experiments and simulations to validate their theory.In this paper,for the reducer in the directly buried fields,undertook the following work:The first chapter describes the reducer's background and significance of the research.Summarized of the reducer's development and current status of research which related to this topic in domestic and overseas,raised the existing problems in the study of reducer and select the research methods and contents of this topic.The second chapter doing the stress analysis for the reducer of the directly buried heating pipe lines in the petrochemical industry fields,directly buried heating fields and other fields,screened out the closest to the actual situation theoretical calculations.In the petrochemical industry fields,stress analysis for reducer mainly in the case of subject to a single internal pressure,proposed the range of limit stress,and propose strengthen and reinforcement measures.But in the directly buried heating fields,to consider the stress situation which is the reducer subjected to in the combined effect of the internal pressure,soil friction and axial stress.And compare and analyze the data of calculating the wall thickness of first and second order reducer and the maximum cyclic temperature difference which can meet the strength condition of first and second order reducer in different fields.And lists the proposal radial length of the reducer.The third chapter using finite element analysis software-ANSYS to simulate and analyze the stress of the directly buried heating reducer which be in the most adverse situations-anchoring section.Concretely,in different internal pressure,temperature and displacement conditions,simulate and analyze reducer which the different diameters and different weld neck ways,different radial length.Obtained stress distribution characteristics of reducer.Compare and analyze the different stress distribution of two different welding methods straight sections weld neck concentric and oblique sections weld neck concentric of reducer pipe.And gives the relationship of different feature sizes with stress of reducer pipe,in order to provide a powerful numerical reference for the Engineering staffs to select the welding methods,select the structural way and determines the feature size of reducer pipe.This numerical reference can help the Engineering staffs to select the reducer pipe which can be the best stress and most able to meet the actual engineering.The forth chapter reference the fatigue life analysis of directly buried heating pipes,use the fatigue life analysis to analyze the reducer.Draw the theoretical calculation method which is suitable for reducers' fatigue life.And simulation the fatigue life of reducer through the ANSYS software.The fifth chapter using the large-scale finite element analysis software ANSYS establish the DN500X450 reducer double welds model as the representative.Using ANSYS's thermal analysis and structural analysis functions accompanied by his life and death element technique,do the welding heat process's heat-structure coupling simulation for reducer pipe.Obtain the distribution characteristics of temperature field and residual stress field of reducers.The sixth chapter summarizes the research and conclusions of the previous chapters of this article.And suggestions and directions for future research.