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The ring compression test is reexamined and the validity of the test method is discussed. It is concluded that the ring compression test has been shown to be valid only in principle and in relation to other methods, which are not independently accurate and are based on similar assumptions. An estimate of the error in the calculation of flow stress and friction is not possible. Values for these parameters that are independently shown to be accurate are not available. Indirect means must be used to further establish the accuracy and validity of the method. Processes contributing to total energy utilization during the deformation of the ring are identified. Factors that contribute to inaccuracy are identified and discussed. These include the influence of the material, geometry, and frictional condition on the changes in dimension of the ring, the existence of regions of zero velocity on the ring surface, misinterpretation of the condition of maximum friction, bulging of cylindrical elements throughout the ring and roll-over as processes contributing to the total power utilization, and discrepancies in the consideration of the minimum power condition.
ring compression test, flow stress, friction factor, bulging, energy balance, forging
Manager, Westinghouse Electric Corp., Pittsburgh, PA