Study On Mechanical Properties Of Spigot Ductile Iron Thermal Pipe

With the rapid development of the economy and the acceleration of urbanization,the central heating area of China’s urban areas is increasing year by year.As one of the core links in the heating system,if the thermal pipeline can further improve the construction efficiency of the pipeline,ensure the safety of the operation of the pipeline,and improve the working life of the pipeline,it will be of great significance to China’s urban central heating project.In order to cope with the development of China’s heating industry and new needs,the industry proposed the idea of socket ductile iron pipes being applied to thermal pipelines.This paper compares the advantages and disadvantages of traditional thermal steel pipes and ductile iron thermal pipelines,analyzes the limitations of current steel thermal pipelines and analyzes the working characteristics of socketed ductile iron pipes,and studies the mechanical properties of ductile iron thermal pipelines.In this paper,three kinds of plug-in ductile iron thermal pipes with different pipe diameters are used as the research objects,and the finite element analysis software Workbench is used to establish a refined three-dimensional finite element model,and the mechanical properties of ductile iron thermal pipes under vehicle static load and thermodynamic coupling are studied.The main contents are:(1)The force analysis of buried thermal pipelines is carried out,the force calculation theory of existing buried pipelines is discussed,and the classical theoretical solution and finite element simulation results are compared and analyzed by example.It is found that the theoretical solution of classical buried pipeline calculation is conservative compared with the finite element calculation result,and the larger the buried depth of the pipeline,the greater the deviation between the finite element result and the theoretical solution.(2)The stress characteristics of ductile iron thermal pipelines under the static load of vehicles were analyzed,and the effects of different vehicle loads and buried depths on the mechanical properties of thermal pipelines were studied.The vertical displacement of the pipe and the section deformation of the thermal pipeline increase with the increase of buried depth.The vertical displacement of thermal pipelines and Mises stress under vehicle static load are proportional to the vehicle load.Under the action of vehicle load and earth pressure,with the increase of pipeline burial depth,the Mises stress of pipeline first decreases and then increases,and there is an optimal buried depth in theory.(3)Analyze the stress situation at the bearing socket of ductile iron pipe under the static load of the vehicle,and study the stress distribution law and vertical displacement at the bearing socket of the pipe under different vehicle effects.Under the action of vehicle load,the maximum stress and displacement maximum of pipeline Mises are located at the socket,and the stress distribution law at the socket of the pipeline is similar with the change of vehicle load,but the value is different.(4)Establish a model of double-pipeline ductile iron thermal pipeline,consider the influence of the temperature field between the supply and return pipes,calculate the thermal coupling of the pipeline,and consider the influence of different temperature,internal pressure and other parameters on the stress distribution law of the pipeline.Due to the structural characteristics of socket ductile iron thermal pipeline,thermal stress can be well avoided,so that temperature load is no longer one of the important factors affecting the safe operation of thermal pipeline.