A perfectly plastic material has been employed as a model material in simulation to analyze numerically the ring compression process, especially to examine the deformation patterns along the die/workpiece interface, which is strongly related to the frictional condition at the contact boundary. The main objective is to provide the deformation characteristics in detail in ring compression, especially at the tool/workpiece interface. The surface flow patterns at the contact boundary in ring compression are summarized and analyzed in terms of surface expansion, surface expansion velocity, pressure distributions exerted on the die surface, relative sliding velocity between die and workpiece, and sliding distance along the die surface. Movement of neutral positions and folding phenomenon are also investigated to see the effect on the deformation patterns at the interface, that is, geometrical change, which is important to measure the frictional condition at the interface using calibration curves. Finite element (FE) simulation using rigid-plastic finite element code has been performed for analysis. The results of this study reveal that surface expansion as well as other surface flow patterns, such as sliding velocity and so on, shows different and distinctive characteristics between low and high frictional conditions at the interface. This is directly related to the movement of neutral positions and folding, which affects the sensitivity of dimensional changes to tribological conditions at the interface.
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