Аннотация:Some problems arising in experimental determination of the strain fate sensitivity of the flow stress, sigma, on the strain rate, xi, are considered. It is pointed out that the strain rate sensitivity index, m, entering the standard power relation sigma = K xi(m), is not identical to the slope M = partial derivative (log sigma)/partial derivative (log xi) of the sigmoidal superplastic curve. The difference between m and M is to be taken into consideration in treating the results of the mechanical tests. Published by Elsevier Science S.A.