Papers by Keyword: Cold Ring Rolling

Abstract: This paper studies the influence of the intermediate annealing on deformation ability of the cold rolled ring. The results show that: intermediate annealing can improve the ability of plastic deformation of the cold rolled ring, ring rupture occurred after 62.5% thickness reduction, on the other side the ring suffering intermediate annealing still be intact by rolling to upon 64.8% thickness reduction. The mechanism of the intermediate annealing improving deformation ability of cold rolled ring is explored by using optical microscopy, scanning electron microscopy, micro hardness tester and other materials characterization methods. It is found that after intermediate annealing, the amount of carbide particles significantly reduce and the hardness decrease. Meanwhile, dissolution of partial carbides occur during the cold ring rolling process, and with the increasing of the cold rolling deformation, the quantity of the dissolution of cementite in pearlite will increase, which resulting in the improvement of the deformability of the cold rolled ring.

Abstract: A single-point load will be applied on the ring in the cold ring rolling process when the ring vibrates violently. This arouses hourglass in finite element simulation of the process using reduced integration element. A one-point quadrature element with hourglass control developed by Hu is used, and the user-defined control parameters are not required. Hourglass energy can be reduced to 3 percent of the internal energy. The element is applied to simulation of a pure radial cold ring rolling with rectangular section. Compared with the experimental results, the simulation results are proved to be accurate. Key-Words: one-point quadrature; Hourglass control; finite element; cold ring rolling

Abstract: Hourglass is obviously aroused in cold ring rolling simulation with reduced integration element because of ring vibrating violently and small contact area of ring and rollers. In the developed numerical simulation code named RingForm, two methods are used to control the hourglass. The first method is combination of artificial damping and artificial stiffness. The second is one-point quadrature element with hourglass control, which need not user-defined control parameters. Hourglass energy can be reduced to 3 percent of the internal energy. Using the latter, good elements are acquired, while computational efficiency is obviously lower than the former.

Abstract: Cold ring rolling is a kind of advanced manufacturing technology. During rolling process the ring may be collapsed or deformed unexpectedly under the pressure of guide roll because the stiffness condition is not met. The force of guide roll to ring was obtained by analyzing the forces to ring. The stiffness condition expressions of ring during rolling were shown after constructing the mechanical model. According to the expressions, the effects of several parameters on the stiffness condition were discussed and analyzed in detail, such as position angle of guide roll, friction coefficient and feed rate, etc, which revealed essential reasons of some cases occurring in cold ring rolling. Then the ring blank dimension was deduced based on the ring stiffness condition. The dimensions of ring blank should meet a relationship to ensure the ring stiffness condition to be satisfied during rolling, which can conduct the practical manufacturing effectively. Finally the analysis and effect laws were proved by finite element simulation experiments. The researches could be helpful to control parameter in cold ring rolling effectively for high quality products.

Abstract: Based on the platform ABAQUS, a 3-D FEM model of spirogyrate ring rolling process has been developed to investigate the ring’s deformation behavior and the expansion law of the diameter. According to the FEM analysis, this kind of profile ring rolling process can be divided into two phases, i.e. the profile forming phase and the diameter increasing phase. During the former phase, the deformation of spirogyrate ring focuses on the profile formation and the diameter increases slowly. In the latter phase, the ring diameter expands rapidly. FEA illustrates that the material flowing to the outer diameter areas is greater than that towards the inner diameter areas in the profile forming phase. The maximum PEEQ is in the pit of the outer profile, whereas the minimum PEEQ locates near the end face. The variation of outer and inner diameter of the spirogyrate ring shows monotonic increasing trend during the whole ring rolling process, in which the expanding rate of inner areas is greater than that of the outer areas.

Abstract: The two methods of artificial damping and artificial stiffness are developed in dynamic explicit FEA code for ring rolling. Advantages and disadvantages of artificial damping method and artificial stiffness method are analyzed. A rectangular section cold ring rolling is simulated. The hourglass energy and the ratio of the hourglass energy to the internal energy are compared between the two hourglass control methods. The hourglass control coefficient criterion of the two methods in the cold ring rolling simulation is proposed.

Abstract: The residual stress in cold rolling could decrease the accuracy of ring parts. Because many factors could cause residual stress, it’s difficult to calculate it theoretically. At present, a measurement method was generally used to study the residual stress. For example, X ray could be used to measure residual stress in rings. Through the measurement of residual stress, it could not only obtain the residual stress level after ring rolling, but also validate the finite element model to predict the residual stress distribution. However, because the ring surface was circle, it needs to cut a plane for X ray measure, and it increases measurement inaccuracy. This method only could be suited for qualitative analysis of residual stress in cold ring rolling, and it is not suitable for quantitative analysis of residual stress distribution.

Abstract: The residual stress in cold ring rolling could cause great error to parts quality. Due to the complicated formation of residual stress, it's difficult to calculate theoretically. In present study, measurement method is generally used. According to the shape of ring, cutting method is the best method for measuring residual stress. There were 6 stages in cold rolling deep groove ball bearing race. Electric wire discharge machine was used to cut the rings after rolling in each stage. The radius of rings would change after cutting. According to the derived analytic calculation theory of residual stress, the residual stress could be calculated in different rolling stage. The residual stresses were in the range of 110-200MPa. Compared the measurement results from finite element simulation results, the greatest difference was 20%, which was in accepted rang. Through calculation results of six stages in cold ring rolling, it could found that the residual stress increased with the increase of deformation, the straightening stage was benefit to decrease residual stress.

Abstract: Analytic calculation and Finite Element Method simulation are used to research the relationship between friction and bitten condition in cold ring rolling. It is found: if the ring can’t be bitten in groove, rolling process will be stopped. The rolling force will increase rapidly, which will cause the breakage of rolls and equipment. When the feed velocity and other technical parameters are kept unchanged, the bitten condition will be disappeared with the process of ring rolling even if the ring can be bitten at the beginning stage.

Abstract: A special elasto-plastic dynamic finite element code named RingForm has been developed to analyze cold ring rolling process. Central difference method was introduced to solve the dynamic explicit finite element equations. Strain state was estimated by the value of yield function of the last and the present time step. To reduce the accumulative error caused by elasto-plastic constitutive relations, the radial return algorithm was employed. In comparison with the experimental results, the cold ring rolling process of a ring with rectangular section has been simulated to verify the accuracy and stability of the system solver.