The Equal Strength Formula Design Of Elbow Wall Thickness And Optimization Of Ox-core Thermal Pushing Process

Bend pipe is widely used as one of important parts in the industry field, and bend pipe has an important purpose in the petroleum, chemical, marine, aviation and nuclear industry. In the industrial production, many pipeline transportation network are required to withstand high temperature, high pressure. When the fluid inside the pipe turns, the fluid will form a large impact on the convex side of the bend pipe which causes a pressurized zone on the convex edge and causes a decompression zone on the concave edge. So the bend pipe also becomes stress concentration position. However, due to the limitation of the process technology, it has become the main reason for bend pipe damage that the convex side wall become thin even cracking because of tension and the concave side wall become thicken even wrinkling because of compression, when the bend pipe is molding. Therefore, accurate stress analysis has become an important prerequisite for the structural design of the elbow, and reasonable thickness design of the elbow is needed to put forward.The characteristics when natural gas flows in elbow have been simulated by the fluid software FLUENT, the relation between the parameters and the pressure of the internal wall was analyzed and the pressure distribution model of 90 degree elbow was given. Through the stress analysis of the bend pipe, three principal stresses and the equal strength formula of the wall thickness was obtained. The forming process that bend pipe was pushed through the ox-core was analyzed by means of the finite element simulation software ABAQUS, and the relation between the different process parameters and the wall thickness of the bend pipe was compared. The optimum process parameters were obtained. The concrete research content is as follows:(1) The flow characteristics of natural gas in 90 degree bend pipe was simulated by means of the computational fluid dynamics software FLUENT, and the pressure distribution law of the bend pipe was analyzed.(2) By changing the gas flow parameters and bend geometry parameters, the flow of the natural gas in bending pipe has been simulated in 48 conditions. The database of bend pipe pressure has been created, and the relation between the different parameters and the pressure was analyzed.(3) With the aid of mathematical fitting software lstOpt, the elbow 3d model of wall pressure was established on the basis of the pressure database. Combined with the pressure model, the stress state of the bend pipe was solved, and the equal strength formula of the wall thickness was obtained by the third strength theory.(4) The forming process that bend pipe was pushed through an ox-core was simulated by means of the finite element simulation software ABAQUS, and the relation between the different process parameters and the thickness distribution of the bend pipe wall was analyzed. and the optimum process parameters were obtained.