Papers by Keyword: Straightening

Abstract: Flatness is an important quality parameter of heavy plates and it is generally achieved through cyclic elastoplastic deformation of the plate in a hot roller leveller following the rolling and cooling processes. To investigate and optimize the hot plate levelling (straightening) process, Finite Element (FE) simulations are widely used. Generally, flow curves with isotropic hardening are used for hot plate levelling simulations. However, the plate material might exhibit kinematic hardening, due to the load reversal that is seldom considered due to laborious high temperature cyclic material characterization. The current work aims at understanding the implications of considering kinematic hardening within hot heavy plate levelling simulations. Hot uniaxial and cyclic material characterization of S355 steel at 1000 °C is performed and the corresponding stress-strain curves are extracted. Using an inverse modelling technique, the associated isotropic and kinematic hardening models are calibrated. The cyclic data showed that the S355 steel exhibits kinematic hardening and the Chaboche kinematic hardening model is suitable to model this behaviour. Hot levelling simulations of plates with isotropic and kinematic hardening models showed a noticeable difference in the roll reaction forces and local curvature of the plate during the process while the resulting flatness of the final plate is not very sensitive to the material model for the investigated scenarios.

Abstract: Considering the initial straightened residual stress of rail and the actual geometrical , we established a three-dimensional contact model of real wheel-rail rolling using ANSYS software. The variation of internal residual stress effected by the wheel repeated rolling was numerically simulated and computed by the explicit dynamic software ANSYS/LS-DYNA, and the variation rules of residual stress during the manufacturing process are obtained. Results show that The longitudinal residual stress decrease with the increase of rolling times, which changed significantly in rail head after 5 repeats, and reached a stable state after 10 repeats

Abstract: Straightening process is to achieve the best standard and improve geometric quality of products caused by heat treatments and internal structural changes. The straightening of the guide rail was analyzed using the load-deflection straightening model. In this paper, three dimensional FE simulation of the reverse bending and straightening of the steel bar conducted as part of the research to numerically investigate for the mechanical engineering applications are presented. This paper is focused on the straightening precision of the guide rail and springback prediction using finite element method. According to the experimental results, by using numerical simulation with finite element analysis (FEA), the relationships among the maximal loading stroke and straightening stroke with the cross-section shape will be gained, and also the result curves were discussed qualitatively. The appropriateness of the simulation procedures employed in this work is represented for similar condition that is a good agreement between the finite element method and experimental results.

Abstract: Residual stresses and lack of straightness appear during the cooling of sheet piles where the initial temperature field is not homogeneous. To meet the standards, the long hot rolled pieces are straightened using a series of rollers placed alternately above and below the pieces with shifts which create a succession of bendings. The process is modeled to study the impact of the industrial parameters (the duration of the cooling and the rollers positions), to improve the final geometry and to reduce the residual stresses. Tests are carried out on this structural steel to observe the material behavior, then material laws are chosen and the parameters of these laws are defined using an inverse method. Two sets of material data are obtained: for the first one, the hardening is supposed to be isotropic, and for the second one, additional tests are performed to describe isotropic and kinematic hardenings. The cooling followed by the straightening is then simulated by the finite element method with these two sets of data. The comparison of the rollers forces, the deformation and the residual stresses show the impact of the kinematic hardening on such a process where the material undergoes a succession of tensions and compressions. The real forces applied by the rollers, the real curvature of the interlocks at the end of the straightening process and the distribution of the residual longitudinal stresses measured on the web using the ring core method are used to validate the numerical model.

Abstract: In this paper, we studied the large deformation and the small deformation method based on the research of the existing system of straightening theory and considered the characteristics of copper-clad steel to find a proper straightening scheme for this new composite materials. the advantages and disadvantages of the method are also compared. the straightening scheme for straightening effect and parameters is a decisive role before all kinds of straightening parameter determination. But at present, there isnt a equipment for the straightening of this new material.

Abstract: Based on Roller Straightening Theory and Elastic-Plastic Beam Research, A Appropriate Mathematical Model of Straightening has Set up.The Author Regards the Tube as a Continuous Bending Beam and Discuss in Detail the Relationship between the Straightening Force and the Bending Moment. Calculating the Amount of Deflection for Tube. in this way ,it Provided a Scientific Basis for the Copper-Clad Steel Tube Straightening Parameter Set and Engineering Application.

Abstract: With the highest product performance, quality and reliability requirements, oil casing is the most demanding service conditions in the oil and gas fields. However, when solving with thin-walled seamless steel pipes by the existing straightening theory, the cross section distortion phenomenon shall not be considered, and when the proportion of diameter to wall thickness increases, an ideal straightening effect can't be obtained. With the elastic-plastic bending straightening theory, this paper analyzes straightening process of thin-walled seamless steel pipes, studies the relationship of the flattening rate, deflection and straightening force in thin-walled pipes straightening, deduces the best reduction calculation method in the practical six roller skew rolling straightening machine, and in the meantime, results of several steel pipes flattening rate are compared.

Abstract: As there was no precise theoretical model for predicting the stress of deformation zone while straightening thin-walled tube, some technological parameters depended mostly on the experience of workers and on the results of trials, therefore by means of the membrane shell theory the equilibrium differential equations of stress is obtained firstly, then we analyze the strain of deformation zone, finally lead to a new theoretical model for predicting the stress in the elastic and plastic zone. Subsequently the simulated experiments have been done, the results show that the theoretical calculations coincide well with the simulated results, the errors are within 1％of the calculations, it is testified that the model is correct and efficient for the thin-walled tube straightening.

Abstract: Copper is important to the national economy as a kind of raw material, the Copper metal with higher purity is got by electrolysis in generally. In order to ensure the uniform space between cathode and anode when they are in electro-groove, to attain the better quality of cathode copper and raising production efficiency, verticality of the cathode and anode must be well. So it is very necessary to straighten the Copper starting sheet to acquire the better verticality, this paper adopt the roller type straightening machine to straighten the Copper starting sheet by analysis and comparison according to the material and structure characteristic of Copper starting sheet . In order to test the straightening ,this paper will use the ANSYS/LS-DYNA to simulate straightening machine to meet the need of company.

Abstract: Copper is important to the national economy as a kind of raw material, the Copper metal with higher purity is got by electrolysis in generally. In order to ensure the uniform space between cathode and anode when they are in electro-groove, to attain the better quality of cathode copper and raising production efficiency, verticality of the cathode and anode must be well. So it is very necessary to straighten the Copper starting sheet to acquire the better verticality, this paper adopt the roller type straightening machine to straighten the Copper starting sheet by analysis and comparison according to the material and structure characteristic of Copper starting sheet .this paper will analysis and research the straightening parameter of straightening machine .