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지창운(Chang Woon Jee),지수민(Su Min Ji),변종복(Jong Bok Byun),전만수(Man Soo Joun) Korean Society for Precision Engineering 2022 한국정밀공학회지 Vol.39 No.8
The fundamental flow models of metallic materials at room temperature, including the Ludwik, Hollomon, Swift and Voce models, were evaluated in terms of tensile test with an emphasis on the necking phenomena and post-necking behavior, to emphasize their limitation in satisfying tensile strength and Considère condition as well as the pre-necking and post-necking strain hardening. To resolve this limitation and enhance the applicability of the new proposed flow model to typical strain hardening materials, the Ludwik-Swift blended flow model is proposed after investigation into three blended flow models among the Ludwik, Voce and Swift models. Results revealed that there is no interpolation-based blended flow model of the fundamental flow models for the example flow curve exhibiting typical strain hardening but that the extrapolation-based combination of them can provide an engineering solution when the Ludwik and Swift models are blended. It was revealed that the reason for their good matching lies in the distinct difference in the strain hardening exponent, between the Ludwik and Swift models in the case of metallic materials with typical strain hardening.
고변형률에서 진응력-진변형률 곡선의 표현을 위한 새로운 구성방정식의 제안
엄재근(Jae Gun Eom),지창운(Chang Woon Jee),전만수(Man Soo Joun) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
In this paper a new constitutive law is presented for modeling the material behavior of the true stress-strain curves in room temperatures. The problems of the Hollomon’s constitutive law, which has been most commonly used, are given from the standpoint of the tensile test. An accurate method of acquisition of stressstrain curves over large strain up to 1.0 from the tensile test results of engineering stress-strain curves is introduced. A new constitutive law is proposed by modifying the Hollomon’s constitutive law with emphasis on the tensile test. The validity of the presented constitutive law is verified by applying it to the tensile test of an annnealed SWCH10A bar, drawn after rolled, and comparing the experiments and the predictions.