Papers by Mohamed Ali REZGUI
Inventions, Mar 8, 2024
This paper aims to optimize a pulsed electrophoretic deposition (EPD) process for TiO 2 films. Th... more This paper aims to optimize a pulsed electrophoretic deposition (EPD) process for TiO 2 films. This is accomplished by determining the optimal configuration of the coating parameters from a robust optimization perspective. The experimental study uses a composite central design (CCD) with four control factors, i.e., the initial concentration (x 1 in g/L), the deposition time (x 2 in s), the duty cycle (x 3 in %), and the voltage (x 4 in V). The process responses that should all be maximized are the photocatalytic efficiency of the thin film (De) and three critical charges, which characterize the adhesion failure, i.e., L C1 : the load at which the first cracks occurred; L C2 : the load at which the film starts to delaminate at the edge level of the scratch track; and L C3 : the load when the damage of the film exceeds 50%. This paper compares the robust optimization design of the EPD process using two methods: the robust design of processes and products using the stochastic frontier (RDPP-SF) and the surface response and desirability function methods. The findings show that the RDPP-SF method is superior to the response surface-desirability method for the process responses De and L C2 because of non-natural sources of variation; however, both methods perform comparably well while analyzing the L C1 and L C3 responses, which are subjected to pure random variability. The parameters setting for the process robust optimization are met in run 25 (x 1 = 14 g/L, x 2 = 150 s, x 3 = 50%, and x 4 40 V).
International Journal of Material Forming, Aug 16, 2019
This work presents an experimental study of aluminum sheet forming. It shows the performances of ... more This work presents an experimental study of aluminum sheet forming. It shows the performances of a steam hydroforming process. The new forming technique is based on both temperature and pressure to make a sheet form. These parameters are linked to the water vaporization process into a cavity covered by the blank. The performances are deduced by comparing the results obtained from the steam tests with those acquired at room temperature. Performances are expressed in terms of forming loads, surface creation, and forming limits. The experimental results show that the use of the steam temperature as a factor could decrease the limit loads necessary for the forming operation and increase the surface creation. On top of improving forming loads and surface creation, increasing steam temperature induces a clear improvement of forming limits.
HAL (Le Centre pour la Communication Scientifique Directe), Apr 1, 2008
This paper presents a numerical methodology which aims to improve 3D thin sheet hydroforming proc... more This paper presents a numerical methodology which aims to improve 3D thin sheet hydroforming processes. This methodology is based on elastoplastic constitutive equations accounting for non-linear anisotropic hardening. The experimental study is dedicated to the identification of material parameters from the global measure of sheet displacement, thickness evolution and internal pressure expansion. Applications are made to study the effect of die shape, anisotropic flow and hardening law on the hydro-formability of sheets.
Advanced Materials Research, 2013
Coupled constitutive equations, formulated in the framework of the thermodynamics of irreversible... more Coupled constitutive equations, formulated in the framework of the thermodynamics of irreversible processes accounting for isotropic hardening as well as the isotropic ductile damage are used to simulate numerically, by the Finite Element Analysis, 3D metal hydroforming processes. The experimental study is dedicated to the identification of stress-strain flow and damage parameters by using the Nelder-Mead simplex algorithm optimization from the global measure of displacement and force. Applications are made to the simulation of thin sheet hydroforming using different at different temperature to show the efficiency of the proposed methodology and to localize plastic instability, thinning of sheet and damage initiation under complex forming conditions.
Advanced Materials Research, 2015
In this paper, a new procedure for the identification of constitutive elastoplastic models couple... more In this paper, a new procedure for the identification of constitutive elastoplastic models coupled with an isotropic damage variable under large strains is presented. It is a statistical approach used for experimental characterization and identification based on a design of experiments of numerical simulations of mechanical characterization tests. The parameters for a reference material are determined by multiple linear regression as a function of shape indices.The material of reference is mild steel E24; it was characterized in a series of tensile tests of thin plate specimens. The Swift hardening law coupled with an isotropic damage variable that was identified by introducing in the established formulations shape indexes extracted from the experimental tension/elongation curves.The number of simulations required for the identification of the parameters of the reference material is roughly 18% of the number required by the inverse method (simplex).
Journal of Biomechanics, 1994
Nous etudions la parallelisation de la procedure de recherche de solution d’un probleme en Progra... more Nous etudions la parallelisation de la procedure de recherche de solution d’un probleme en Programmation Par Contraintes (PPC). Apres une etude de l’etat de l’art, nous presentons une nouvelle methode, nommee Embarrassingly Parallel Search (EPS). Cette methode est basee sur la decomposition d’un probleme en un tres grand nombre de sous-problemes disjoints qui sont ensuite resolus en parallele par des unites de calcul avec tres peu, voire aucune communication. Le principe d’EPS est d’arriver statistiquement a un equilibrage des temps de resolution de chaque unite de calcul afin d’obtenir une bonne repartition de la charge de travail. EPS s’appuie sur la propriete suivante : la somme des temps de resolution de chacun des sous-problemes est comparable au temps de resolution du probleme en entier. Cette propriete est verifiee en PPC, ce qui nous permet de disposer d’une methode simple et efficace en pratique. Dans nos experimentations, nous nous interessons a la recherche de toutes les ...
L'ergonomie d'un poste de travail, de conduite ou de pilotage est devenue une preoccupati... more L'ergonomie d'un poste de travail, de conduite ou de pilotage est devenue une preoccupation importante pour de nombreux concepteurs. La qualite de l'assistance que peuvent eventuellement apporter des logiciels de conception assistee par ordinateur (cao) est conditionnee par la qualite des modeles biomecaniques qui sont introduits pour simuler les mouvements de l'operateur humain. L'introduction de ces modeles est rendue delicate par la complexite anatomique et fonctionnelle des membres d'un etre humain (systemes mecaniques articules redondants dont chaque articulation a plusieurs degres de liberte). Sur le mannequin graphique man3d, la simulation du geste d'atteinte du membre superieur se heurte au probleme de l'indetermination du pivotement du bras qui peut etre defini comme la rotation de l'ensemble du membre superieur autour d'une droite imaginaire reliant l'epaule au point terminal de la main. L'objectif du present travail etait de...
Vocational and Technical Education, 2010
The study aims at investigating individual performance of trainees who are subjected to two inter... more The study aims at investigating individual performance of trainees who are subjected to two interrelated courses, namely, CAD and CADCAM. First, a three factor design experiment has been conducted to measure the effects of trainer (A, B), trainee secondary certificate (Scientific and Industrial) and trainee college esteem (High, Low) on the mean score of CAD and CADCAM obtained by the population of trainees graduating in 2006 through 2008. Altogether, eight combinations having each eight subjects (trainees) have been considered. The second part of the study carried out investigation of 25 trainee's scores gained in CAD and CADCAM training courses by means of a 4-plot exploratory data analysis (EDA) technique. The following regression models which deal with the correlation between Exam and Continuing Assessment scores are established and individual performances of trainees are outlined. Key words: ANOVA, regression model, normal distribution, hypothesis testing, EDA, CAD/CAM.
Materials
Titanium dioxide thin films immobilized over treated stainless steel were prepared using the puls... more Titanium dioxide thin films immobilized over treated stainless steel were prepared using the pulsed electrophoretic deposition technique. The effects of process parameters (deposition time, applied voltage, initial concentration, and duty cycle) on photocatalytic efficiency and adhesion properties were investigated. To optimize the multiple properties of the thin film, a response surface methodology was combined with a desirability optimization methodology. Additionally, a quadratic model was established based on response surface analysis. The precision of the models was defined based on the analysis of variance (ANOVA), R2, and the normal plot of residuals. Then, a desirability function was used to optimize the multiple responses of the TiO2 thin film. The optimum values of applied voltage, catalyst concentration, duty cycle, and deposition time were 4 V, 16.34 g/L, 90% DC, and 150 s, respectively. Under these conditions, the decolorization efficiency of tested dye solution reached...
Mechanics & Industry
The paper aims to optimize the characteristic performances of friction stir welding of high-densi... more The paper aims to optimize the characteristic performances of friction stir welding of high-density polyethylene in order to predict failure modes in weld nugget and interfacial zones. Three replicates of a face central composite design are employed to estimate the effects of parameters process, on the transversal flow stress and strain of the seam and to understand root causes, which may lead to structural defects such as the onset of cracks and the seam-base metal rupture. The study findings disclose that maximum responses are obtained when the tool rotation speed is set middle and both the feed rate and the plunged surface are set high. The transversal flow stress of the welded seam is found highly sensitive to the plunged surfaces and at a lesser degree to the rotation speed, whereas, the transversal flow strain of the welded seam is mostly sensitive to the rotation speed and at a lesser degree to the plunged surfaces. For the microscopic analysis, it is shown that at low rotati...
Concurrent Engineering
A generic procedure for robust design in developing products and processes, which is referred to ... more A generic procedure for robust design in developing products and processes, which is referred to as RDPP-SF has been proposed. The method uses the stochastic frontier model to encompass both stochastic noise (e.g. manufacturing unit-to-unit variation, and measurement errors) and special-cause variation (e.g. environment, customer use, wearing, and deterioration noises). Even then, the RDPP-SF method has fallen short of tackling robust design of multi-objective problems, and its applicability is restrained to the performance characteristics of magnitude type (i.e., “the larger is the better” or “the smaller is the better”). Aiming at these limitations, the article seeks to address the robust design of the multi-objective problems using the RDPP-SF method. This is performed by reassessing the procedural scheme of the RDPP-SF method and the statistical significance of the hypothesis test (H0: γ = 0 vs H1: γ > 0) at 5% level. Depending on the statistical significance of the test (H0:...
The International Journal of Advanced Manufacturing Technology
Materials Sciences and Applications, 2016
Mécanique & Industries, 2009
Materials Sciences and Applications, 2016
B. Eng project topic: Study, design and manufacture of a 5 kW aero-generator blade Model 1983 Bac... more B. Eng project topic: Study, design and manufacture of a 5 kW aero-generator blade Model 1983 Baccalaureate Mathematics and Technologies, Tunis Training Sessions Consultant to the Ministry of Higher Education and Scientific Research and member of the mechanical engineering committee in charge of the organization of entrance and upgrading tests for training programs dedicated to High Institutes of Technology (ISET), Tunisia 2002
The paper has investigated the friction stir welding process of a high density polyethylene which... more The paper has investigated the friction stir welding process of a high density polyethylene which has been experimented under three operating parameters, namely tool rotation speed, tool feed and tool plunged surface. Main effects as well as interactions are assessed with regard to a process response longitudinal flow stress (� LF ). Next, optimal factor settings are sought so that � LF is maximized. The experimental design which has been employed in this work is two replicates of a 2-levels full factorial plan duly augmented by four runs at the design center point. It is used replicates along with center points to better investigate pure process errors, lack of fit, and pure curvature as well as testing significance of linear combinations of second order effects, if any found significant.
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Papers by Mohamed Ali REZGUI