Research On The Roll Shape Of Two-roll Bar Straighteners Based On Spatial Contact And Development Of Parameterized Software

As a kind of profile with simple section,bars are mainly produced through extrusion,drawing,rolling,etc.During the production process,various kinds of quality defects like different degree of bending or distortion,out-of-roundness of the section,etc.may be caused due to uneven pressing or cooling,saw cutting or shearing under hot state or the like.Therefore,straightening becomes the only and important approach to improve and increase the dimensional accuracy and the shape accuracy of bars effectively in the finishing stage,and it determines the final quality and precision of the products.Compared with multi-roll straighteners,two-roll straighteners have such advantages as high straightening accuracy,compact structure,comprehensive bar straightening ability,etc.However,the domestic theories for design of two-roll straighteners at present can hardly satisfy the requirements of actual production,and the straightening rolls designed independently are not ideal in terms of contact state and have unsatisfactory performance,including uneven distribution of residual stress after straightening,etc.Hence,enterprises are restricted in production of high quality bar products,and it's of important practical significance to explore a widely applicable method to design roll shapes that can realize good contact state during straightening,so as to develop the straightening equipment manufacturing industry and improve the competitiveness of high-value-added products of our country.With the working principle of straighteners as the starting point,this thesis analyzed the changing relationship among stress,strain and various curvatures of bars under the bending action of the roll-gap during the straightening process.Then,based on the space coordinate transformation theory,it proposed a new method to design roll shape curves based on spatial contact by assuming full-length contact between the bar and the straightening roll during the straightening process.The thesis further made a numerical analysis on and finite element simulation of the method comparatively with two methods for roll shape design commonly used at present.It was found through the analysis and the simulation that the method has such advantages like high solution accuracy,simple and easy solution process,good contact during the straightening process,etc.With the design method,not only can the roll shape of a roll with variable curvature be designed,but also the roll shape curve under different bending conditions can be solved accurately and rapidly;in addition,the contact between the straightening roll and the bar can be judged according to the bending state of the bar axis during the straightening process to provides certain theoretical foundation for the adjustment of parameters of the straightening process.The thesis also developed a parameterized software for design and simulation of roll shapes by hybrid programming with C#.Net and the numerical calculation software MATLAB,the 3D modeling software Soild Works or the software for FEM simulative analysis,Marc.The method for designing roll shape curves based on spatial contact has advantages like wide scope of application,good contact during straightening,etc.and it makes it possible to design,roll shape curves of straightening rolls fast and conveniently.Besides,it provides certain theoretical foundation for the configuration of parameters of the straightening process.With the parameterized software developed based on it,it's convenient for engineering and scientific research personnel of enterprises to design roll shape curves for different straightening requirements and to generate supporting documents for the simulation of the straightening process.This thesis has important practical significance for the development of straightening equipment manufacturing industry and the improvement of the competitiveness of high-value-added products of our country.