Abstract
The results of three different upsetting tests on four commercial steels are presented. The specimen geometry is shown to have a marked effect on the free surface ductility. The so-called collar test obviates the need of a grid of lines on the free surface of the specimen from which the axial, εz, and hoop, εgq, strains are usually determined. The collar test results in reduced fracture strains vis à vis those achieved when compressing a circular cylinder. Consequently fracture can be induced earlier when compressing more ductile materials. It is demonstrated that the fracture strains from the three different upsetting tests do not lie on a straight line fracture locus, as proposed by Kuhn. A knowledge of the εgq-εz strain path can lead to an evaluation of the stress history on the equatorial free surface of an upset specimen. In turn the stress history permits the assessment of various ductile fracture criteria. Two models were examined in the present work, neither of which suited all the experimental data. A maximum shear stress fracture criterion appeared to be more appropriate for the present set of experiments. The deleterious effect of MnS inclusions on the fracture strains is exhibited by comparing the behavior of AISI 1045 and 1146 steels.
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Sowerby, R., Chandrasekaran, N. The cold upsetting and free surface ductility of some commercial steels. J. Applied Metalworking 3, 257–263 (1984). https://doi.org/10.1007/BF02833653
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DOI: https://doi.org/10.1007/BF02833653