A numerical, experimental, and phenomenological investigation of cross-wedge rolling.

摘要

Cross wedge rolling (CWR) is a new metal forming process in which a cylindrical billet is plastically deformed into an axisymmetrical part. CWR offers considerable economic benefits, because it is extremely fast, quiet, and automatic. However, its widespread application has been inhibited by the tendency of workpiece failure and the difficulty in understanding the complicated metal deformation process. In addition, the trial-and-error nature of the design of the dies is still a matter of art rather than science, which adds tremendous cost and lead time to the manufacturing process. Herein lies the underlying theme of this research: using state-of-the-art finite element techniques, innovative CWR models, and experimental data as a basis, fundamental relations and the physical nature of CWR will be developed to make CWR a more viable manufacturing process.; In this work, a new and innovative numerical model of CWR was developed using advanced explicit dynamic finite element method (FEM). The three-dimensional nonlinear deformation process from the round bar to the final shaft, tool-workpiece interfacial slip, stress and strain distributions were predicted over a wide range of CWR operating conditions which include varying the forming angle, knifing angle, coefficient of friction, workpiece cross sectional area reduction, etc. The three major failure mechanisms in CWR, (1) initial slip at the die and the workpiece interface, (2) porous void formation in the workpiece, and (3) internal cracking in the workpiece, were studied. The workpiece rotational condition in flat-wedge CWR was derived, and failure conditions predicted by analytical and numerical analyses were compared.; Experimental studies were performed in order to validate the FEM model. The prototype flat wedge CWR machine and a high speed filming system were used to measure the interfacial slip. The effect of CWR tool parameters and rolling conditions on tool-workpiece interaction and slip, stress and strain distributions in the workpiece materials was presented serving as a CWR design guideline. Recommendations for future work were proposed.