Abstract
There is a general opinion that flow stress of materials should be the property, which is independent of the type of the tests, which is used to determine this stress, and to the sample dimensions. This statement was, in general, confirmed when inverse analysis was applied to the interpretation of the plastometric tests. The channel test was an exception, which was explained on the basis of influence of micro-shear bands in the material. There were, however, some observations showing that in ring compression tests some discrepancies from the flow stress values determined from other tests, can appear. The objectives of the present work are formulated on the basis of the assumption that different states of strains in the ring compression, depending on the shape of the ring, may lead to different tendency to generation of micro-shear bands in the material. Thus, finite element simulation of ring compression were performed assuming various dimensions of rings and various friction coefficients. States of strain was determined in each tests and comparison was performed. Comparison was made to flow stress measurements published in the literature. Conclusions concerning correlation between flow stress and state of strains were drawn. Sensitivity of the flow stress with respect to the sample dimensions and friction coefficients was determined.