Analysis Of Bending Rule And Forming Defects Of Metal Pipes

Metal pipes have many applications in aerospace,automotive,marine,and other industries.According to the needs of users,people often want to bend the pipe into a certain geometric shape,that is,the bending of the pipe.In the bending process of the pipe,many uncontrollable forming defects often occur during the bending process of the pipe,affecting the quality of the bend pipe,and greatly reducing the bending efficiency of the pipe.The common defects are mainly the bending rebound of the pipe,the thinning and cracking of the outer pipe wall of the curved section,the thickening and wrinkling of the inner wall,and the distortion of the cross section of the pipe.In order to produce the required bends efficiently and efficiently,it is particularly important to analyze and study the basic properties,bending rules and possible defects of the pipes.The main contents of this paper are as follows:The stress-strain of metal pipes under bending conditions is analyzed.Based on elasticity-exponentiation material model.Linear relation was used to describe the stress-strain relationship in the elastic deformation zone near the neutral layer.Power function was used to describe the stress-strain relationship in the plastic deformation zone.According to the springback theory,the wall thickness of the pipe is considered,the approximate calculation formula of bending springback angle of metal pipe is deduced.Calculation results show that the ratio of the springback generated in the elastic deformation zone to the total springback is very small.The size of the rebound angle is related to the material's own parameters,and it is also related to the bending parameters such as bending angle and radius of curvature.The elastic-power reinforcement model is adopted in the analysis of the bending rebound of the pipe.The elastic deformation zone and the plastic deformation zone are taken into consideration,which are more in line with the actual model of the metal.Compared with the method of calculating the bending springback of pipes using geometric methods,the effect of pipe wall thickness was taken into account in this paper.The approximate calculation formula for the calculated rebound amount is programmed,and the approximate value of the rebound amount can be conveniently calculated according to the input parameter values.The wall thickness variation and cross section distortion of the pipe during the bending process were analyzed.The finite element method was used to analyze the bending processof the metal pipe,and the effects of relative bending radius,pipe wall thickness,bending speed,etc.on the wall thickness variation and the flatness ratio of the pipe during bending were analyzed.