The Finite Element Analysis Of The Stress About Directly Buried Heating Welded Tee

The piping tee,elbow and reducer which are often used in the directly buried heating are weak links,the tee of these three weak parts should be given the priority.Therefore,the research of design method which is security and economic of piping tee is necessary.The realization of the tee is often used in practice welded tee,the study of directly buried heating welded tee is rare at home and abroad which have given some empirical formulas.Aiming at the status quo,this paper analyses the change rule of stress about welded tee under the action of an internal pressure alone and under the action of internal pressure and temperature load together using the ANSYS finite element simulation method.The main content of this paper includes six parts.First chapter elaborates selected topic background and significance of the paper,and briefly expounds the research methods and contents of the paper through introducing the research status of directly buried heating tee pipe fittings at present.The second chapter introduces directly buried heating pipe load types and different stress produced by the different load,classifies modes of pipeline failure which may be led by stress,points out clearly the modes of pipeline failure are plastic deformation and low cycle fatigue damage.The third chapter introduces the processing technology of various type of tee and the advantages of manufacturing welded tee.The fourth chapter analyses and compares the calculation methods of infinite plastic deformation and low cycle fatigue damage stress for welded tee at home and abroad,introduces calculation methods of straight pipe and the wall thickness for welded tee at home and abroad,mainly aiming at the two failure modes of tee.Calculate the critical stress based on the Parr's green-minas formula and S-N curve In Europe code in order to determine whether the tee under the different requirements and levels meets the requirements of the safety of the low cycle fatigue damage.In the fifth chapter,exert pressure on the load by pressure load,temperature load and displacement load on the welded tee model using ANSYS finite element software.Using the third strength theory analysis:When pressure load a separate function,maximum stress appears in the shoulder,analysis of the stress distribution rule,conclusion tee branch pipe length of the model L=10 m(branch after bend section),short branch pipe length D=200 mm(branches bend section)before the biggest stress is about 1.1 times of 1/4 model;(b)when the pressure and temperature load effect together,tee maximum stress appears in the abdomen,obtained with the tee branch pipe length L increases,the maximum stress value increases linearly,basic tee deformation has a tendency to increase;with the increase of branches short tube length D,tee maximum stress value has a tendency to decrease,the three links of deformation failure has a tendency to decrease;(c)welded tee branch pipe size increasing(head size remains the same)or head size(branch pipe size remains the same),the maximum stress is not always increase;(d)for the tee of the same position,the internal pressure and temperature stress value can be superimposed.In sixth chapter,summarize the research achievements of this paper,point out the deficiency of this article,and put forward the research direction of welded tee in the future.