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Hegde’s instability mechanics for the prediction of forming limit in sheet metal forming

Author(s): G.S. Hegde | J.R. Nataraj | R. Sridhar

Journal: Archives of Computational Materials Science and Surface Engineering
ISSN 1689-9210

Volume: 1;
Issue: 3;
Start page: 155;
Date: 2009;
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Keywords: Sheet metal instability | Von-Misess yield criteria | Interface theory | Hegde’s Instability Mechanics (HIM)

Purpose: The purpose of the paper is to investigate the Hegde’s instability mechanics for the prediction of forming limit in sheet metal forming.Design/methodology/approach: Hegde’s Instability Mechanics (HIM) paves way for explaining the effects of diffuse instability and localization due to necking in sheet metal forming. For different ranges of stress ratios, the ratio of strain differentials has been computed and hence the forming limits are predicted.Findings: Basing the formulation of HIM on the von Misess yield criterion and applying the interface theory (briefed in appendix) the state-of- the-art purpose is deemed to be well served and demonstrated. Interface theory to explain in simple terms, gives the optimal decision variables in an ‘n’ dimensional hyper-space. The concept of HIM is demonstrated on isotropic and anisotropic materials. The anisotropic materials show better stability than isotropic materials in sheet metal forming. However the geometric instability is analyzed with the assumptions that the thickness stresses are negligible and biaxial state of stress persists in sheet metal forming.Practical implications: The observations are based on the theoretical findings for which the experimental validation exists in the reviewed references.Originality/value: To the sincere knowledge of authors, is both different and unique of its kind in sheet forming mechanics needing horizontal exploration by potential researchers.
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