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1

Effect of MWCNTs content on the characteristics of A356 nanocomposite

Rashad R. M., Awadallah O.M., Wifi A. S.

Journal of Achievements in Materials and Manufacturing Engineering

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2013

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Vol. 58, nr 2

74--80

EN

Purpose: The objective of the present paper is to study the effect of Multiwalled Carbon Nanotubes (MWCNTs) content on the mechanical properties of the A356 hypoeutectic aluminum- silicon based nanocomposite. Design/methodology/approach: The semi-solid route stir casting technique is used for composite processing. MWCNTs and Aluminum powder are premixed by ball milling and green compacted to form small billets. Al-MWCNTs billets are added to the melt and incorporated by vigorous mechanical stirring. The mechanical and metallurgical properties of the produced composite are characterized by, scanning electron microscopy (SEM), optical microscopy, and tensile testing DIN 50125. Findings: MWCNTs are successfully incorporated into the A356 melt up to 1.5 % weight fraction. SEM analysis revealed a uniform dispersion of MWCNTs with good interfacial bonding between the matrix and the MWCNTs. The ultimate tensile strength and elongation of the produced composite are increased by 34% and 250% respectively compared to their corresponding values of monolithic alloy. Research limitations/implications: The research was carried out based on MWCNTs only with a range of percentage additions; it could be extended to single Walled CNTs and graphene sheets with different percentage additions. Stirring time and speed as well as heat treatment can also be applied as further study. Practical implications: This work helps in introducing novel technique in dispersing Nano particulates in metal matrix composites. This could be good potential for new developed composites. Originality/value: A novel approach for MWCNTs reinforcement addition technique is implemented. This technique results in a uniform dispersion of MWCNTs with good interfacial bonding between the matrix and the MWCNTs.

2

Towards an optimized process planning of multistage deep drawing: an overview

Wifi A. S., Abdelmaguid T. F.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 1

7--17

EN

Purpose: To present a concise literature review on the optimization techniques used for the single stage and multistage deep drawing process, and to identify directions for future research. A perspective on a comprehensive optimized computer aided process planning is provided for multistage deep drawing processes. This is an integrated rule base/dynamic programming/finite element approach that minimizes the total number of stages and heat treatment needed. Design/methodology/approach: Relevant research is classified according to the major process parameters and the optimization techniques used. Main features and major outcome of the applications are presented. Findings: There is a lack in the literature in providing a comprehensive approach for optimizing the multistage deep drawing process. Research limitations/implications: Directions for future research towards integrative models for optimizing the multistage deep drawing process that take into consideration economic as well as operational objectives are identified. Originality/value: This paper provides a guide for researchers in the field of deep drawing and identifies some directions for future research that can be pursued. It also gives some insights to practitioners in that field on how integrated models can improve the economics and the quality of the process planning decisions for multistage deep drawing.

3

Springback prediction in V-die bending: modelling and experimentation

Osman M. A., Shazly M., El-Mokaddem A., Wifi A. S.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 38, nr 2

179-186

EN

Purpose: A theoretical model is developed for the air-bending process and V-die bending experiments are conducted. Based on comparisons between springback ratios predicted using the developed theoretical air bending model and the V-die bending experiments, a semi-empirical formula for predicting springback ratio in V-die bending process is suggested. The validity of this formula is verified using finite element simulations as well as comparisons with the results of two other independent sets of experiments. Design/methodology/approach: A theoretical model for air bending is developed and compared with published models. Experimental work on V-die bending is conducted. The experimental results are used in a correlation analysis to develop a mathematical expression for predicting springback ratio of V-die bending as a correction of the spring back ratio of air bending. These results are verified by comparisons with finite element simulations as well as with other independent sets of experiments. Findings: Springback ratios for V-die bending could be predicted using the developed semi-empirical formula. For a given limit of the striking (coining) force, springback ratios are affected by sheet thickness, bend radius, and material parameters. Research limitations/implications: This work suggests a methodology for the prediction of springback ratio in V-die bending. This work can be extended by studying the effect of anisotropy on the developed springback ratio. Practical implications: The developed semi-empirical formula could be practically used in determining the springback ratio for V-die bending. The selection of the sheet thickness and bend radius are critical parameters that affect springback ratios. Originality/value: A semi-empirical formula is suggested for the prediction of springback ratio in V-die bending. This is viewed as a correction of the theoretically predicted air bending springback ratios. This formula could be of help to those working in sheet metal forming industries.

4

A study on the UNDEX cup forming

El Mokadem A. E., Wifi A. S., Salama I.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 37, nr 2

556-562

EN

Purpose: This work investigates the use of the underwater explosion (UNDEX) for the free and plug assisted cup forming processes. Design/methodology/approach: A 3D finite element model is built to simulate the process of the UNDEX cup forming using ABAQUS finite element code. Johnson-Cook (JC) material plasticity model is used to represent strain rate sensitivity of the used materials. Johnson- Cook damage criterion is employed to detect the onset of damage in the cup forming process. Findings: Both relatively hard and soft plugs are considered and the effects of using different plug materials on cup profile, strains and the limiting drawing ratios are given. The onset of damage in this process is also indicated. The results suggest that a relatively hard plug can enhance the control of the cup shape and the uniformity of strain distribution leading to increased limiting drawing ratio. Research limitations/implications: This work suggests a methodology for the prediction of shape, different strain distribution, the limiting drawing ratio and the energy required for UNDEX cup forming process. Practical implications: This study could be useful in non-conventional high energy rate forming industry. Originality/value: The study reveals the possibility of producing flat-bottomed cup by the relatively hard plug assisted UNDEX forming technique.

5

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

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2006

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Vol. 18, nr 1-2

291--294

EN

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.

6

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

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2006

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Vol. 17, nr 1-2

245--248

EN

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.