New Technology Of Four-point Reciprocating Bending And Straightening Of Profiles

Profiles occupy an important position in engineering applications.With the increasingly fierce market competition,the society has put forward further demands for the quality and function of profiles.Defects will occur after rolling or transportation of profiles,which not only reduces the surface quality of profiles,but also affects their straightness.In the traditional straightening method,the loading force acts directly on the specimen,while straightening,other defects will be formed on the profile surface.At the same time,most of the methods are only applicable to a certain profile with high cost and low utilization rate.Based on the above problems,a new pressure straightening process is proposed in this paper.Based on the theory of elasticity of plane bending with small curvature,the unified curvature theorem of reciprocating bending and the over-bending straightening process,a new straightening method for profiles-four-point reciprocating bending straightening process is proposed.The process fixes the two ends of the profile on the special clamp,sets four stress points on the clamp,and the indenter and the support directly act on the clamp instead of the specimen,thus reducing the area of air correction.By replacing clamps,profiles with different sections can be straightened.The process has the advantages of low cost and wide straightening range.In this paper,the rectangular section profile is taken as the research object.Reciprocating bending straightening model of 304 stainless steel and 20 steel was established by ABAQUS software.Four-point reciprocating bending loads were carried out on profiles with different initial curvatures and shapes under different bending radius.The distribution of stress and strain in the process of reciprocating bending and straightening and the variation of curvature radius with bending times after springback were analyzed.It is found that after reciprocating bending,the difference of initial shape can be eliminated and the curvature can be unified to the same value.The larger the bending radius is,the faster the uniform curvature speed is and the better the effect is.It is found that the residual stress of the profile after straightening is small and evenly distributed.The straightness is less than 0.2%,which meets the industry standard.Finally,the reciprocating bending straightening experiment was carried out on an electronic multi-functional material testing machine,and the law consistent with the simulation results was found.The correctness of four-point reciprocating bending straightening process and its feasibility in engineering application are verified.