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Azouaoui K.,University of Science and Technology Houari Boumediene | Azari Z.,Metz National School of Engineering | Pluvinage G.,Metz National School of Engineering
International Journal of Fatigue | Year: 2010

In the current study, experimental investigations are carried out to determine the response of glass/epoxy cross ply laminates to repeated low-velocity impact. The material response is evaluated in terms of damage progression with the number of impacts. Damage is evaluated by visual and SEM inspection. Damage parameter D is based on the evaluation of the loss of material bending stiffness and evolution of damage parameter is given versus number of impacts. Rectangular composite laminates of size 280 mm by 180 mm and nominal thickness of 5.4 mm are subjected to low-velocity impact fatigue loading at two energy levels (4 and 5 J). Delamination has been found as the main factor of increasing of damage parameter. Impact crater participate less to this increase at the beginning of live duration but has greater influence on D parameter evolution at the end. Experimental results indicate that the damage evolution versus number of impacts can be represented by "S" shape curve and thus indicates the importance of the first impacts. © 2009 Elsevier Ltd. All rights reserved.

University of Lorraine, Metz National School of Engineering, Arts, INSA Rennes and French National Center for Scientific Research | Date: 2012-11-07

According to a thermomechanical treatment process for a titanium alloy including between 23 and 27% niobium in atomic proportion, between 0 and 10% zirconium, and between 0 and 1% oxygen, nitrogen and/or silicon, the following steps are performed: a) an increase of a sample of the alloy to a temperature higher than 900 C., b) a fast quench, c) a severe cold strain, d) an ageing treatment at a temperature included between 200 and 600 C., the time of the ageing treatment being included between 10 seconds and 10 minutes. Alloy obtained by this process and prostheses made from such an alloy.

Garcia-Gonzalez D.,Charles III University of Madrid | Rusinek A.,Metz National School of Engineering | Jankowiak T.,Poznan University of Technology | Arias A.,Charles III University of Madrid
Composite Structures | Year: 2015

This paper deals with the mechanical behavior of polyether-ether-ketone (PEEK) under impact loading. PEEK polymers are the great interested in the field of medical implants due to their biocompatibility, weight reduction, radiology advantage and 3D printing properties. Implant applications can involve impact loading during useful life and medical installation, such as hip systems, bone anchors and cranial prostheses. In this work, the mechanical impact behavior of PEEK is compared with Ti6Al4V titanium alloy commonly used for medical applications. In order to calculate the kinetic energy absorption in the impact process, perforation tests have been conducted on plates of both materials using steel spheres of 1.3. g mass as rigid penetrators. The perforation test covered impact kinetic energies from 21. J to 131. J, the equivalent range observed in a fall, an accidental impact or a bike accident. At all impact energies, the ductile process of PEEK plates was noted and no evidence of brittle failure was observed. Numerical modeling that includes rate dependent material is presented and validated with experimental data. © 2015 Elsevier Ltd.

Leonard F.,University of Aleppo | Martini A.,Metz National School of Engineering | Abba G.,Metz National School of Engineering
IEEE Transactions on Control Systems Technology | Year: 2012

A helicopter maneuvers naturally in an environment where the execution of the task can easily be affected by atmospheric turbulence, which leads to variations of its model parameters. This paper discusses the nature of the disturbances acting on the helicopter and proposes an approach to counter the effects. The disturbance consists of vertical and lateral wind gusts. A 7-degrees-of-freedom (DOF) nonlinear Lagrangian model with unknown disturbances is used. The model presents quite interesting control challenges due to nonlinearities, aerodynamic forces, underactuation, and its non-minimum phase dynamics. Two approaches of robust control are compared via simulations with a Tiny CP3 helicopter model: an approximate feedback linearization and an active disturbance rejection control using the approximate feedback linearization procedure. Several simulations show that adding an observer can compensate the effect of disturbances. The proposed controller has been tested in a real-time application to control the yaw angular displacement of a Tiny CP3 mini-helicopter mounted on an experiment platform. © 2006 IEEE.

Vernadat F.B.,Metz National School of Engineering
Annual Reviews in Control | Year: 2010

Enterprise networking refers to any kind of organization structures in which two ormore geographically dispersed business entities need to work in interaction. This can happen within a single distributed enterprise (networked enterprise) or among several enterprises (network of enterprises), including the extended enterprise or virtual organizations. This concerns any kind of organizations, e.g. industrial firms, public organizations or large government agencies. Enterprise interoperability is a sine qua noncondition for enterprise integration and networking. It largely relies on information and communication technologies (ICT), especially Internet computing. The paper uses the European Interoperability Framework (EIF) as a foundational baseline to first discuss technical, semantic and organizational aspects of enterprise interoperability and networking and finally to address some open research issues. © 2010 Elsevier Ltd.

Leonard F.,Metz National School of Engineering | Abba G.,Metz National School of Engineering
IEEE Transactions on Automatic Control | Year: 2012

In the control of delayed systems by a finite spectrum assignment (FSA) , in the control law, the integral over the time delay of a function of past control appears. This assignment is in fact available for continuous delayed process independently of the stability of the latter, which is very interesting since Smith predictor is usually only used with stable processes. Nevertheless, in case of FSA control implementation, this integral control should be sampled so that spectrum assignment is not necessarily preserved and an unstable discrete closed loop can be obtained , . In this technical note, FSA integral control robustness with respect to prediction time uncertainty is analyzed for an unstable continuous linear system. A transformation approach is also proposed to understand the effects of different ways of sampling control laws. In a last part, a case study shows how Simpson approximation of integral control law leads to an unstable digital closed loop. © 2011 IEEE.

Khatab A.,Metz National School of Engineering
Journal of Intelligent Manufacturing | Year: 2015

This paper deals with imperfect preventive maintenance optimization problem. The system to be maintained is assumed to be subject to random deterioration. To reduce the risk of failures, the proposed maintenance model takes into account two type of maintenance actions, namely corrective maintenance (CM) and preventive maintenance (PM). The system undergoes PM whenever its reliability reaches an appropriate value, while CM is performed at system failure. After a given number of maintenance actions, the system is preventively replaced by a new one. Both CM as well as PM are considered imperfect, i.e. they bring the system to an operating state which lies between two extreme states, namely the as bad as old state and as good as new state. The imperfect effect of CM and PM is modeled on the basis of the hybrid hazard rate model. The objective of the proposed imperfect PM optimization model consists on finding the optimal reliability threshold together with the optimal number of PM actions to minimize the expected total maintenance and replacement cost per unit of time. A mathematical model is then proposed. To solve this problem an algorithm is provided. A numerical example is also given to illustrate the proposed maintenance model. © 2013, Springer Science+Business Media New York.

Dinzart F.,Metz National School of Engineering | Sabar H.,Metz National School of Engineering
International Journal of Solids and Structures | Year: 2011

In this work, a micromechanical model for the estimate of the magneto-electro-elastic behavior of the magnetic-piezoelectric composites with coated reinforcements is proposed. The coating is considered as a thin layer with properties different from those of the inclusion and the matrix. The micromechanical approach based on the Green's functions techniques and on the interfacial operators is designed for solving the magneto-electro-elastic inhomogeneous coated inclusion problem. The effective magneto-electro-elastic properties of the composite containing thinly coated inclusions are obtained through the Mori-Tanaka's model. Numerical investigations into magneto-electro-elastic moduli responsible for the magneto-electric coupling are presented as functions of the volume fraction and characteristics of the coated inclusions. Comparisons with existing models are presented for various shape and orientation of the coated inclusions. © 2011 Elsevier Ltd. All rights reserved.

Coulibaly M.,Metz National School of Engineering | Sabar H.,Metz National School of Engineering
International Journal of Solids and Structures | Year: 2011

Predicting the overall behavior of heterogeneous materials, from their local properties at the scale of heterogeneities, represents a critical step in the design and modeling of new materials. Within this framework, an internal variables approach for scale transition problem in elastic-viscoplastic case is introduced. The proposed micromechanical model is based on establishing a new system of field equations from which two Navier's equations are obtained. Combining these equations leads to a single integral equation which contains, on the one hand, modified Green operators associated with elastic and viscoplastic reference homogeneous media, and secondly, elastic and viscoplastic fluctuations. This new integral equation is thus adapted to self-consistent scale transition methods. By using the self-consistent approximation we obtain the concentration law and the overall elastic-viscoplastic behavior of the material. The model is first applied to the case of two-phase materials with isotropic, linear and compressible viscoelastic properties. Results for elastic-viscoplastic two-phase materials are also presented and compared with exact results and variational methods. © 2010 Elsevier Ltd. All rights reserved.

Pluvinage G.,Metz National School of Engineering | Capelle J.,Metz National School of Engineering
International Journal of Fracture | Year: 2014

In this paper, four kinds of characteristic length parameters used in a local notch fracture criterion are presented: (1) a characteristic length ρc generally connecting to the notch radius, (2) a characteristic distance Xc considered as intrinsic to material and connected to the microstructure, (3) a critical distance d0 considered as intrinsic to material and connected to the fracture process zone, (4) an effective distance Xef considered as a characteristic of the stress distribution. Each approach is discussed. The paper ends with the author's opinion about the different methods. © 2014 Springer Science+Business Media Dordrecht.

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