Stress Analysis Of 40°~90° Directly Buried Heating Horizontal Angle Elbow

With the improvement of the quality of life,people put forward higher requirements for the living environment.In order to provide a warm and comfortable living environment for residents,the domestic central heating industry has been grow vigorously.Due to the directly buried laying has remarkable advantages,it is widely used in central heating projects.Different from overhead laying and trench laying,the force condition of directly buried heating pipe has its own characteristics.As an important part of the pipeline,the directly buried heating elbow undertake pipeline steering,avoiding obstacles and line-leading.However,because of the force of solid,the force condition of directly buried heating pipe has become more complex.So far,there is not a mature method of stress analysis,especially for the 40 °～90° directly buried heating Angle elbow.In view of this,ANSYS finite element software was used to carry on the numerical simulation of 40°～90° directly buried heating horizontal angle elbow,which was to take analysis of the stress distribution and its influencing factors.The simulation results had been drawn out,providing the basis for the design of buried pipeline engineering.The paper is of significance for improving the design technology of directly buried heating pipe,reducing engineering investment,decreasing network maintenance,overall improving the safety of the buried pipeline and heating reliability.The paper has completed the following work with the 40°～90° directly buried heating horizontal angle elbow in large diameter:1、Taking analysis of the stress distribution of directly buried heating Pipe Making classification of all kinds of the loads which act on the pipe.And the function,characteristics and application situation of each load.Carring on analysis of limit state,including plastic-flow,cyclic plastic deformation,fatigue damage,the whole instability,the local unstable.The failure mode has been pointed out.2、Stress calculation methods of directly buried heating elbow in"Technical specification for directly buried hot-water heating pipeline in city"and "Technical code for stress calculation of steam/water piping in power plant"were respectively introduced.At the same time,taking analysis of stress influencing factors,which provides a reference for the following finite element simulation.And the results will be compared with the finite element simulation results.3、The finite element method and finite element software ANSYS were introduced briefly.Material parameter setting and characteristics of the unit used were introduced in detail.Building the finite element model of horizontal elbow.Grid division,and the grid independence assessment,according to the needs of different research content of the model to apply load and define the appropriate boundary conditions,and then the finite element solution.4、Select a long combination of different arm pipe is simulated,the extraction of the neutral line of the pipe outer surface and near the inner arc inner surface of the equivalent stress maximum value were compared and identified in 40 °～90° degree bending angle range in directly buried horizontal bend equivalent stress maximum at neutral line near to the outer surface of the.It is concluded that when the two pipes are straight arm uses the combination of arbitrary length,as long as arm length is equal to the sum of the,40°～90°degree bending angle bend of the maximum equivalent stress value remains unchanged.5、Simulated in different working conditions.It is concluded that the maximum value of equivalent stress is the equivalent of bending elbow under different pipe diameter,different angle of view,different curvature radius,different wall thickness and different working cycle.Origin software is used to calculate the results of the calculation of the different factors and the maximum equivalent stress of the elbow.Found that the bending angle,the radius of curvature and the wall thickness increased,the maximum value of equivalent stress of elbow was decreased,with the increase of the temperature difference of the circulating working,the maximum value of the equivalent stress was gradually increased.6、Simulating bent pipe on both sides and set the fixed pier,solving the maximum limit on the arm length Lmax,a was found to 40°～90° degree bending angle bend with the increase of crease angle phi,maximum limit arm length Lmax,a gradually increasing.At the same time,with the increase of length of arc length,the maximum limit of the length of Lmax,a gradually increased,and with the angle of the elbow angle increased,the amplitude of a increased gradually decreased with the increase of Lmax,a.