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2 Journal of Achievements in Materials and Manufacturing Engineering

2 2006

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Optimization of the blank holder force in cup drawing

Gharib H., Wifi A. S., Younan M., Nassef A.

Journal of Achievements in Materials and Manufacturing Engineering

2006

Vol. 18, nr 1-2

291--294

Purpose: Develop an optimization strategy for the cup drawing process in order to produce a defect free deep drawn cup. Design/methodology/approach: An optimization strategy for the blank holder force (BHF) scheme is proposed which searches for the BHF scheme that minimizes the maximum punch force and avoids process limits. This strategy is applied to the linearly varying BHF scheme and compared to the constant BHF. Findings: The optimized linear BHF scheme resulted in an improved cup forming when compared to that produced by the constant BHF scheme. The BHF scheme is optimized for different cases of drawing ratios and die coefficients of friction in order to analyze the nature of the optimum linear BHF scheme. It was found that the slope of the linear BHF scheme increases with the increase in the drawing ratio in a linear manner. Also, the intercept of the function showed a nearly linear variation with the drawing ratio. A general equation is deduced for the optimum blank holder force at any drawing ratio for the cup under study. Research limitations/implications: The proposed optimization strategy can be applied to BHF schemes other than the linear one, and with different objectives. In this scheme, the objective has been the minimization of the maximum punch load. Other objectives like minimum punch work may be implemented. Practical implications: The proposed optimization strategy can be applied to any deep drawn part if an analytical or numerical model is available for this part. Originality/value: The research presented in this paper offers a new optimization strategy which can be useful in controlling the process parameters to produce a defect free deep drawn part using optimum process conditions.

An analytical incremental model for the analysis of the cup drawing

Gharib H., Wifi A. S., Younan M., Nassef A.

Journal of Achievements in Materials and Manufacturing Engineering

2006

Vol. 17, nr 1-2

245--248

Purpose: of this paper Develop an analytical model for the cup drawing process to solve for the induced stresses and strains over the deforming sheet at any stage of deformation until a full cup is formed. Design/methodology/approach: An analytical model is developed for the cup drawing process by determining the variation of stresses and strains over the deforming sheet. The model uses finite difference approach and numerical procedures to solve for equilibrium, continuity, and plasticity equations in an incremental fashion. Findings: The developed analytical model results showed good correlation with experimental ones from the literature. Also, the analytical model was found to be useful in conducting parametric studies in order to determine how the different process parameters can affect the deforming cup. Research limitations/implications: This paper includes the development of an analytical model to analyze the deep drawing of axisymmetric cups. This model is then used as the solution engine for the optimization of the blank holder force for such cups avoiding failure by wrinkling or tearing. This model also gives an insight of the modes of deformation in the deep drawing process. Practical implications: This paper is part of a procedure that leads to the optimization of the blank holder loading scheme. The full procedure as presented in the two parts of the work may be applied in industry to minimize the maximum punch load or the work done during deep drawing process by modifying the blank holder force and at the same time avoid failures by wrinkling or tearing. Originality/value: Developing a predictive/corrective technique for solving the unknown boundaries of the deforming sheet.