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2 Archives of Computational Materials Science and Surface Engineering

2 2009

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Interface driven optimisation of springback in stretch bending of autobody panels

Hedge G.S., Shivaprasad J., Sridhar R.

Archives of Computational Materials Science and Surface Engineering

2009

Vol. 1, nr 3

168-173

Purpose: Analytical determination of springback in the stretch bending of autobody double curved panels and optimization of parameters like yield strength and thickness of plate, have been the prime purposes of this paper. Design/methodology/approach: The elasto plastic behaviour governed by Hooke's law and Holomann's law, has been solved using interface theory, the original contribution of author. In the process Hegde's interface modulus has been coined, which depends on both modulus of elasticity and the plastic coefficient. Findings: The linearized functions of change of springback and stretch tension are solved for optimization, again using interface theory briefed in the Appendix. Practical implications: The published models of springback optimization being complicated, a need has been felt to formulate computationally easy and confidently accurate model of springback determination. The theoretical deliberations are demonstrated on materials based on the data obtained from the published references. Originality/value: The authors are confident of the originality and do claim authentically the novelty in the workout of the analysis. The interface theory applied at several stages in the analysis gives the optimal solutions to variables in the hyperspace defined by a linear system with redundancy in unknown variables.

Hedge's instability mechanics for the prediction of forming limit in sheet metal forming

Hedge G.S., Nataraj J.R., Sridhar R.

Archives of Computational Materials Science and Surface Engineering

2009

Vol. 1, nr 3

155-160

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.