Numerical Simulation Study On Cold Rolling Process Of Bearing Rings

Cold ring rolling technology is a cross and combination of rolling technology and mechanical manufacturing, which decreases the thickness of ring and enlarges the diameter of ring via the cold ring rolling mill. It has many advantages, such as high material utilization ratio, reduced procedures, high quality and precision, energy saving and improved working environment. Compared with traditional method, the ring rolling technology is of great social significance and economic performance.Considering fully characteristics of cold ring rolling, simulation model is created to simulate the cold rolling of deep groove ball bearings. Influence of the parameters (such as mold structure, feed velocity, rotational speed and material parameters etc.) on roll force, axial spread and forming quality is studied. The main contents and conclusions of this paper are as follows:(1) Based on ABAQUS software, a three-dimensional elastic-plastic FEM model is established. The elastic-plastic mechanics theory and numerical simulation technology of large deformation are adopted according to the different stages of the deforming process basing on the deforming mechanism of cold ring rolling.(2) Proper feed velocity, motion track of guide roll and the mass scaling coefficient are determined. On basis of earlier work, designing formula of feed velocity is defined according to bite conditions and penetration conditions. The following motion guide rolls are adopted. The motion track is a segment of arc and the center is decided by the axis of drive roll, the distance of different times is computed and used to control the motion of guide rolls. Mass scaling can accelerate the simulation, so proper mass scaling coefficient is determined as 10 by comparison of the results under different mass scaling coefficients.(3) Influence of the mold structure and process parameters is studied. Proper mould structure can not only avoid fishtail effect, but also give a result of high quality and less machining amount. In order to gain a stable process, higher feed velocity should be took at the beginning of the process, while lower feed velocity should be took latterly. The roll force decreases and the quality can be improved by increasing the rotational speed of the drive roll. But slipping happened more frequently and higher power cold ring rolling mill is needed. Therefore, proper rotational speed of drive roll should be determined according to the production requirements.(4) Influence of the material property parameters, feed velocity and their coupling effect to forming process is studied. Limiting spread structure is adopted. when strain hardening exponent, Young's modulus and Yield strength are chosen respectively in the range of 0.10-0.40, 100GPa-400GPa, 50MPa-400MPa. Constant feed velocity is used and the scope is 1.1mm/s-4.0mm/s, influence of them to forming process is studied.1) The roll force grows with the increase of feed velocity. The influence of strain hardening exponent to roll force is similar to true stress-strain wave under different strain hardening exponent. In the earlier stage, the roll force is easier to be influenced by Yield strength, but subsequently, the influence decreases. Young's modulus has little influence on the roll force.2) When feed velocity increases, shaping effect turns worse. When strain hardening exponent and Young's modulus grow, side spread of the end face decreases, but when feed velocity increases, influence of them decreases. Side spread of the end face is hardly affected by Yield strength.3) The work piece is easier to get good shape when feed velocity is low, but when feed velocity increases, the condition of homogeneous deformation is improved. While strain hardening exponent grows, the maximum deformation decreases and the condition of inhomogeneous deformation is improved. When feed velocity increases, the influence of strain hardening exponent decreases. When Young's modulus grows, the maximum deformation and the inhomogeneous deformation degree increases. Yield strength has little influence on the inhomogeneous deformation. 4) The deformation of end face is easier to be effected by feed velocity at the place close to inner surface. When feed velocity grows, the influence of strain hardening exponent, Young's modulus and Yield strength decreases.5) When feed velocity increases, equivalent plastic strain of the inner surface decreases. Strain hardening exponent and Yield strength have little influence on the equivalent plastic strain of the inner surface. The equivalent plastic strain of the groove is affected by Young's modulus, and it grows when Young's modulus increases.