Analytical relations between hardness and strain （分析硬度和应变之间的关系）.pdf

Journal of Materials Processing Technology 186 (2007) 163–173 Analytical relations between hardness and strain for cold formed parts Fazil O. Sonmez ∗, Ahmet Demir Department of Mechanical Engineering, Bogazici University, Istanbul, Bebek 34342, Turkey Received 13 October 2005; accepted 14 December 2006 Abstract Our objective in this study is to establish an analytical relation between hardness and effective strain induced in a metal during cold working. In this way, its hardness can be determined from numerically obtained plastic strains without producing the part and taking measurements. For each of the two most commonly used measures of indentation hardness, Vickers’ and Brinell’s, a separate analytical relation was proposed relying on the previous empirical and numerical studies. The results of the analytical models compared well with the data obtained from the experiments that we conducted. The models were also verified by comparing its predictions with the experimentally determined hardness values reported by previous researchers. The results showed that both of the analytical models can reliably be used to determine hardness distribution within a cold formed part. © 2007 Elsevier B.V. All rights reserved. Keywords: Brinell hardness; Vickers hardness; Flow curve; Effective strain; Cold forming; Steels 1. Introduction the hardness of a part. Trial and error, by producing prototypes, taking measurements and repeating the process, is not a feasible If a piece of metal is cold formed, the resulting plastic strain approach. It is difficult, time consuming, and costly. Estimat- distribution