The Variable Thickness And Equal Strength Formula Design Of Elbow And Ox-core Thermal Forming Process

Elbow is an important part in pipeline transportation,widely used in industries of metallurgy,petroleum,chemical etc.The stress of the bend in the practical engineering is relatively complex,easy to produce stress concentration,is one of the weak link of the pipeline system.When the pipe wall flange by fluid impact pressure is far greater than the bending concave,convex and concave curved edge resulting in uneven stress often leads to bending cracking,explosion and fire vicious consequences.In this paper,the fluid in the flow characteristics of circular cross section 90°bend tube is simulated,according to the bending of the inner wall of the pressure value,by fitting the software to get the pipe internal pressure distribution model;Stress analysis was carried out on the bent pipe,according to the strength theory to design wall thickness in the bent pipe,it is concluded that the wall thickness of the bend mathematical model;Hot push pipe bending forming technology for numerical simulation of the horn mandrel for 3d design,system variable wall thickness pipe bending.The result for the bend in the process of pipeline safety evaluation,the bent pipe wall thickness design,pipe wall thickness design and processing provides the theory instruction,has great value in engineering application.The main contents are as follows:(1)The flowing condition and the pressure on inner surface of ethylene in the 90°elbow pipe were simulated by means of FLUENT software,on the condition of 4 kinds of fluid density p,fluid inlet velocity v,fluid outlet pressure P0,degree curvature k=R/d respectively.Analysis different flow parameters(inlet velocity v,outlet pressure P0,the liquid density p) and geometric parameters(the degree of curvature k,the axial angle a and the circular angle ?)on the influence of pressure,using 1stOpt fitting a curved pipe pressure distribution model is given by,through compared the simulated values by FLUENT with computed values by Equation,the agreement is high,that the maximum relative error between them is only 0.0284%.The conclusion contributes to structural design and safety evaluation of the elbow pipe.(2)The stress analysis of the bent pipe under internal pressure,calculate the axial stress,radial stress,circular stress.The establishment of relationship between the wall thickness and pipe internal pressure distribution model,through the Tresca strength theory.The mathematical model of the wall thickness of the bend strength is given.The conclusion contributes to the design of the variable wall thickness elbow pipe on the condition of different flow parameters and geometric parameters and safety evaluation of the elbow pipe.(3)According to the character of ox horn mandrel that the bending deformation and expanding deformation always maintain a certain proportion relationship,using the variable curvature curve as the axis of the mandrel.The forming process that bend pipe was pushed through an ox-core was simulated by means of the finite element simulation software DEFORM.The relation between the different ox horn mandrel that the bending deformation and expanding deformation and the thickness distribution of the bend pipe wall was analyzed,and the variable wall thickness pipe bending were obtained.The conclusion contributes to the manufacture variable wall thickness of pipe.