Finite element modeling and analysis of cold ring rolling
Cold ring rolling is a complex metal forming process and generally not well understood. In many instances, considerable experience and experimentation is required to develop the process. During the process, plastic deformation behavior namely the plastic deformation state and its development in the deformation zone, has an important effect on the stability of the process. Hence, investigating the plastic deformation behavior in the deformation zone during the process is very significant for predicting the metal flow, controlling the quality of deformed rings and optimizing the process parameters. In this thesis, a study on plastic deformation behavior in cold ring rolling has been carried out through 2D numerical simulation using the LS-DYNA numerical finite element analysis code. The type of deformation behavior is compared with three type of plastic deformation behavior, established in previous studies. One type is that the material in the deformation zone entirely comes into the plastic deformation state at the early stage of the process (Type 1). A second type is that the material in the deformation zone gradually comes into the plastic deformation state during the process (Type 2). The last type is that at the end of process, there is still a rigid zone in elastic deformation or small plastic strain state near the middle radius of the ring blank (Type 3). The theoretical equations for decisive factor for plastic deformation behavior, which is the average amount of feed per revolution and functional relations between the average amount of feed per revolution and various process parameters, are ascertained with the assumption that the change in ring height during the process is negligible. Hence axial rolls are used to restrict the metal flow in axial direction of the ring. The simulation is performed for vi another class of aluminum alloy and the results are explored. The simulation is performed by varying the decisive factors and the results are plotted for the effective plastic strain, vonmises stress and KE/IE ratio v/s time. The distribution of plastic strain through the thickness of the ring is also studied. A study on effect of the plastic deformation behavior on driver roll force was then carried out for both the materials. Through this thesis it was showed that it is required to run the cold ring rolling process at lower driver roll speed and higher feed rate. It is also required to have higher average amount of feed per revolution to achieve homogeneous deformation, uniform strain distribution and higher driver roll force. The results of this thesis in which a 2D FE analysis with plane strain formulation theory is carried out, can be used as a basis for optimizing the process parameters.