Search

GaN High Electron Mobility Transistors (HEMTs) are very promising for radiofrequency applications and especially RADAR operation due to their ability to work at high power densities. However, parasitic effects like traps are a common issue on this type of technology. They have to be properly characterized in order to be compensated. Several measurement methods exists like DLTS or DLOS, mostly consisting in a measurement of a current transient at different junction temperatures. This paper presents a comparison between different extraction algorithms for trapping signatures and the possible impact of their imprecision when extracting the activation energy on measurement data. Furthermore, a more physical model for trap extraction will be presented with its limitations.

International audience; Obsolescence is the fact that an entity (physical or logical) is becoming outdated or no longer possesses the required level of performance. The objectives of this article are twofold. First, it is intended to contribute to the understanding of obsolescence propagation. Secondly, two supporting approaches for the Identification and Assessment phases are proposed: the House of Obsolescence and the System Obsolescence Criticality Analysis. The former allows the mapping of obsolescence propagation via dependencies, whether imposed changes are desired or imposed, by external actors to the system architecture. Whereas, the objective of the latter is to assign an obsolescence criticality index to the identified risks in order to prioritize them for solution or mitigation determination during the analysis phase. The tools make extensive use of the modeled system knowledge through the application of Systems Engineering. The application of these approaches is presented through an illustrative study.

International audience; We present some results on the uniform exponential stability of singularly perturbed linear systems undergoing switching. In absence of dwell-time constraints, the switching parameter can evolve on the same time scale as the fast variables, or even faster. We investigate the effect of switching laws evolving at a time scale comparable with the fast variables, describing the corresponding asymptotic effect on the slow variable. Based on this analysis, we propose stability criteria for the overall system, uniform for small values of the parameter of singular perturbation.

International audience; Technologies, evolving at an ever faster pace, particularly in the electronics and IT sectors, lead inevitably systems to face the problems generated by obsolescence. Clearly, the manufacturer must be able to design systems so that an obsolescence problem has the least possible damaging or undesired consequences. The fact that a system remains as long as possible unaffected by changes imposed by obsolescence is called resilience. It, therefore, determines the ability of the system to continue providing its services while having at least one obsolete component, function or technology. The objective of this research work is to propose a modeling methodology and tools to ensure resilience to obsolescence; this resilience being directly defined by design choices. The methodology is based on the exploitation of modeled dependencies in the architecture of a system. The mapping of dependencies is done using different models obtained by applying a system engineering methodology, ARCADIA. The dependency model is then transformed into Bayesian networks to predict quantitatively not only the consequences of possible obsolescence issues in a given architecture but also to qualify the alternatives. This methodology, called Obsolescence Resilience By Construct, ORByC, is applied to the study of the rail signaling system.

Titanium alloys Ti-6Al-4V, have been broadly utilized in industries, particularly aerospace and medical manufacturing, owing to their good mechanical properties. In this work, high energy CO2 laser cutting of 3 mm-thick titanium alloys sheets is investigated with the aim of estimating the effects of the various laser cutting parameters such as, laser power (Pu), cutting speed (V) and of assist gas pressure (p), on the integrity of the cutting area. The objective of this study is to analyze the cut edge microstructure and to optimize the surface roughness using Taguchi method. Performances denote optimum cutting condition was obtained to be 3 kW for the laser intensity, 2400 mm/min for the cutting speed and 8 bars for gas pressure.

In complex machines, the generation of a Disassembly Plan (DP) which allows a minimum change of disassembly tools and directions, and permits an easy dismounting of wear parts is the main requireme...

Short and long-term stabilities of cementless implants are strongly determined by the interfacial load transfer between implants and bone tissue. Stress-shielding effects arise from shear stresses due to the difference of material properties between bone and the implant. It remains difficult to measure the stress field in periprosthetic bone tissue. This study proposes to investigate the dependence of the stress field in periprosthetic bone tissue on i) the implant surface roughness, ii) material properties of bone and of the implant, iii) the bone-implant contact ratio. To do so, a microscale 2-D finite element model of an osseointegrated boneimplant interface was developed where the surface roughness was modeled by a sinusoidal surface. The results show that the isostatic pressure is not affected by the presence of the bone-implant interface while shear stresses arise due to the combined effects of a geometrical singularity (for low surface roughness) and of shear stresses at the bone-implant interface (for high surface roughness). Stress-shielding effects are likely to be more important when the bone-implant contact ratio value is low, which corresponds to a case of relatively low implant stability. Shear stress reach a maximum value at a distance from the interface comprised between 0 and 0.1 time roughness wavelength $\lambda$ and tend to 0 at a distance from the implant surface higher than $\lambda$, independently from bone-implant contact ratio and waviness ratio. A comparison with an analytical model allows validating the numerical results. Future work should use the present approach to model osseointegration phenomena., Comment: Journal of Orthopaedic Research, Wiley, In press

The objective of this document is to contribute to the modelling of engineering changes and their propagation. Usable in preliminary redesign activities, a new approach is suggested that allows greater efficiency. Given a product model, the idea is to use the experiments to calculate in advance the consequences of potential changes in continuous variables. These consequences are collected, analysed and structured in a dependency model, noted $$\langle \varGamma , \varPhi \rangle$$ , composed of a dependency graph $$\varGamma$$ and its associated set of influence functions $$\varPhi$$ . Bilateral influence functions, associated with arcs, quantify the dependencies between node pairs. Multilateral influence functions, identified by the application of the total differential theorem, define the dependencies between a node and all influential nodes on which it depends. Finally, the relative error is calculated by following the infinitesimal assumption of the total differential for each variables. Our findings show that such a dependency model is informative and allows effective prediction and evaluation of changes. The approach is illustrated by a geometric bicycle model. The results are discussed and future areas of research are finally presented.

In this paper we consider the problem of determining the stability properties, and in particular assessing the exponential stability, of a singularly perturbed linear switching system. One of the challenges of this problem arises from the intricate interplay between the small parameter of singular perturbation and the rate of switching, as both tend to zero. Our approach consists in characterizing suitable auxiliary linear systems that provide lower and upper bounds for the asymptotics of the maximal Lyapunov exponent of the linear switching system as the parameter of the singular perturbation tends to zero.

International audience

International audience; Thin-film piezoelectric materials are advantageous in microelectromechanical systems (MEMS), due to large motion generation, high available energy and low power requirements. In this kind of application, thin piezoelectric films are subject to mechanical and electric cyclic loading, during which damage can accumulate and eventually lead to fracture. In the present study, continuum damage mechanics and asymptotic theory are adopted to model damage evolution in piezoelectric thin films. Our purpose is to develop a new interface model for thin piezoelectric films accounting for micro-cracking damage of the material. The methods used are matched asymptotic expansions, to develop an interface law, and the classic thermodynamic framework of continuum damage mechanics combined with Kachanov and Sevostianov’s theory of homogenization of micro-cracked media, to characterize the damaging behavior of the interface. The main finding of the paper is a soft imperfect interface model able to simulate the elastic and piezoelectric behavior of thin piezoelectric film in the presence of micro-cracking and damage evolution. The obtained interface model is expected to be a useful tool for damage evaluation in MEMS applications. As an example, an electromechanically active stack incorporating a damaging piezoelectric layer is studied. The numerical results indicate a non-linear evolution of the macroscopic response and a damage accumulation qualitatively consistent with experimental observations.

International audience; Preventive maintenance becomes nowadays more and more essential in many industrial applications. In fact, researchers are always looking for new techniques and analysis tools to monitor the dynamic behavior of their machines. In this context, firstly, we deal with the modeling of an electromechanical system which is accounted for by a hybrid model obtained by assembling the mechanical model of a gear element and the electrical model of an asynchronous motor. Secondly, we use Sliding Mode Observers to supervise the gear dynamic behavior. The observers parameters are suitably chosen to ensure rapid and accurate convergence between the real and the estimated system quantities. Finally, a comparative study between three simulations is presented in order to illustrate the observers performances and the influence of the mechanical dynamics on the electrical ones.

This paper describes a geometrical model to quantify minimal joint clearance in overconstrained 2D or 3D linkages when the shapes of components are subject to manufacturing deviations. This important property needs to be computed at the earlier stages of product development for engineers to design and produce reliable mechanisms in the context of mass production. The solution is based on a previous study dedicated to rigid assemblies. The major contributions of this work are the definition of a regularized closure function together with the computation of minimum joint clearance for a mobile linkage. Five examples illustrate the efficiency of the solution.

International audience; In this research, the effect of processing input parameters on the kerf taper angle response of three various material thicknesses of sugar palm fiber reinforced unsaturated polyester composite was investigated as an output parameter from abrasive waterjet and laser beam cutting techniques. The main purpose of the study is to obtain data that includes the optimum input parameters in cutting the composite utilizing these two unconventional techniques to avoid some defects that arise when using traditional cutting methods for cutting the composites, and then make a comparison to determine which is the most appropriate technique regarding the kerf taper angle response that is desired to be reduced. In the laser beam cutting process, traverse speed, laser power, and assist gas pressure were selected as the variable input parameters to optimize the kerf taper angle. While the water pressure, traverse speed, and stand-off-distance were the input variable parameters in the case of waterjet cutting process, with fixing of all the other input parameters in both cutting techniques. The levels of the input parameters that provide the optimal response of the kerf taper angle were determined using Taguchi’s approach, and the significance of input parameters was determined by computing the max–min variance of the average of the signal to-noise ratio (S/N) for each parameter. The contribution of each input processing parameter to the effects on kerf taper angle was determined using analysis of variation (ANOVA). Compared with the results that were extrapolated in the previous studies, both processes achieved acceptable results in terms of the response of the kerf taper angle, noting that the average values produced from the laser cutting process are much lower than those resulting from the waterjet cutting process, which gives an advantage to the laser cutting technique.

International audience; Based on the projector introduced in recent Euler semi-implicit methods, the main contribution of this paper is the reduction of the effect of noise on the sliding surface of the discretized homogeneous differentiator. For that, an adaptation law according to the magnitude of the high frequency noise is proposed to modify the behavior of the projector when the discretized differentiator remains on the sliding surface. In presence of noise, the differentiator will have an asymptotic convergence but will be less-sensing noise. Otherwise, when the differentiator is not affected by noise on the sliding surface, its convergence will be in finite-time. Experimental results are shown in order to highlight the well founded of the contribution.

International audience; Swarm engineering is a systematic application of scientific and technical knowledge to specify requirements, model, design, realize, verify, validate, operate and maintain a swarm intelligence system. In swarm robotics, there is not a well-structured methodology until today for developing robotic swarm systems. Several researchers have developed steps to design swarm robots but these steps are still incomplete. In this paper, we focus on the functional architecture of the swarm robots where we propose a top-down approach to ensure consistency and continuity from requirement level to behavioral level up to the functional and structural levels. This approach is based on the Model-Based Systems Engineering method (MBSE) using the Systems Modeling Language (SysML) where we present the allocations between the functions of each swarm member and the overall swarm behaviors. Then, we will be interested in the architecture of Robot Operating System (ROS) of a swarm behavior where we identify the allocations between the component and the functions of a robot.

This work addresses the problem of developing control algorithms for the control of the aerodynamic lift of wind turbine blades using air injection, taking into account disturbances caused by turbulent perturbations. For this, a test bench is used where the lift of a 2D blade section in a wind tunnel can be controlled by a set of micro-jets close to the trailing edge. Through a continuous, local identification of the lift variations a model-free control that does not need any prior knowledge of the system is proposed. It allows the control of the flow of the micro-jets and stabilizes the lift around a tracking reference. The ability of the proposed control algorithm to track the lift reference when subjected to external perturbations, i.e., gusts, is discussed. In particular, this work demonstrates that the lift can be set to particular values using the proposed control strategy, and can be re-stabilized to pre-gust lift conditions. Experimental results illustrate globally the feasibility of such a control.

This paper proposes a finite contact duration model of a Vibro-Impact Nonlinear Energy Sink (VI NES) for controlling the vibrations of a civil engineering frame structure under seismic input. The device is composed of a container enclosing an inelastic sphere, interacting via a nonlinear viscoelastic dissipative force with the inner walls of the container. As the structure vibrates, the particle bounces within the container, exploring dynamical regimes ranging from periodic collisions to chaos and dissipating energy. Our VI NES is optimized for the El Centro NS (1940) earthquake signal, and its effectiveness in reducing the dynamic response of a ten-story frame structure is investigated. It is also compared with a classical TMD optimized according to the Den Hartog criterion. The main result is that the performance of the VI NES in reducing the top floor maximum displacement is very satisfying. Moreover, sensitivity analyses reveal good robustness of the VI NES to initial conditions and to variations in the properties of the primary structure.

International audience; Collaboration is an interesting solution adopted to improve the levels of sustainability by massifying flows. In this study, we present a new design of a distribution network under uncertainties at two levels in a collaborative context. The proposed network includes suppliers who collaborate to deliver their products to retailers through common platforms. On the other hand, uncertainty is treated in terms of two parameters, namely demands and unit transportation costs.The different used models are validated and analysed by a case study. Computational results provided by the robust model and those given by the deterministic one are compared to evaluate the importance of uncertainty. The effects of uncertainty level on the optimal network configuration are also highlighted.

Metal matrix composites are widely used in modern engineering as a result of the needing for distinct features into the same material, and for presenting such characteristics, the metallic foams have been increasingly used mainly from the mobility industry. Therefore a semisolid processing route for producing an AlSiMg0.5Mn matrix syntactic foam was idealized, by the thixoinfiltration of an industrial waste known as fly ash micro balloons. Preliminary a thorough study of the balloons morphology and chemical composition had been done, as also the AlMg2.5 thixoability through Spectrometry, Differential Scanning Calorimetry (DSC). The process parameters were defined to obtain a homogeneous pore distribution into the matrix and good wettability of balloons analyzed by x-ray micro tomography (Micro CT) and optical microscopy.

Confronted with an increasingly uncertain and fluctuating economic environment characterized by a technological evolution driven by industry 4.0 concepts, companies have to adapt their supply chains in order to improve its competitiveness. They must also implement strategies that allows them to deal with these new challenges. Supply chain modularity offers the opportunity to change and reorganize the structure of the supply chain to meet changing market needs. In this paper, we propose a new framework to design a modular supply chain using Design Structure Matrix and a modularity measurement in Reconfigurable Supply Chain. We also show the importance of integrating the direction of flows, i.e. inbound and outbound flows in the calculation of modularity and, in particular, its impact on lead time. Finally, an illustrative example is developed to validate the proposed measurement.

International audience; Market disruptions and changes make the assessment process of supply chain performance more complex. Hence, the implementation of key indicators to evaluate the ability of the supply chain to cope with these disruptions has received increasing attention. Reconfigurability provide the ability to quickly change supply chain structure and functions by increasing its responsiveness and flexibility to deal with disruptions. This paper aims to analyze the contributions of researchers in the field of performance evaluation under supply chain disruption. A bibliometric analysis is conducted to identify publications dealing with performance evaluation under supply chain disruption field. The analysis started with the selection of articles using the following keywords (Reconfigurability, Evaluation, Supply Chain). Then, the selected articles were analyzed based on the criteria of the bibliometric analysis. The paper aims to capture the current research and potentialresearch related to the evaluation of performance in reconfigurable supply chain under disruption.

International audience; Failure Modes, Effects and Criticality Analysis (FMECA) is one of the well-known methods of quality management that is used for continuous improvement in product or process design. This method uses linguistic expressions and has good information about cause-effect chains. However, it lacks probabilistic information. Transforming it into a Bayesian Network (BN) makes it possible to be used in maintenance for both diagnosis and prediction. The purpose of this paper is to develop a method that uses as much information as possible from FMECA, including frequency and detection to precisely make the configuration of the BN. To build a BN's structure from FMECA, we elaborate a tool to do it systematically. Moreover, we develop an algorithm to set the parameters of a BN obtained. Elicitation methods based on expert knowledge are used when data is not sufficient. A case study of FMECA in the automotive industry is introduced to verify the applicability of the proposed method in an industrial environment.

Motivated by the biaxial plastic dynamic buckling behavior of tubular structures, the particular interest of this work was to develop a non-conventional energy-dissipating system. This system is based on the studying of the experimental behavior of square metallic tubular structures under dynamic complex loading paths. This non-conventional solution aims to enhance the strength properties of the used structures. Accordingly, the well-developed device (the ACTP: Absorption par Compression-Torsion Plastique) has been employed where biaxial loading paths (combined compression-torsion) with different complexities were generated from a uniaxial compressive load. Thus, five inclination angles (30°, 37°, 45°, 53° and 60°) were used to study their effect on the biaxial plastic buckling of square aluminum tubes. This new comprehensive experimental study aimed to investigate the effect of three loading boundary conditions (i.e., simple, intermediate and severe) on the tubes’ behavior. The dynamic deformation, mean collapse load (Pm) and energy absorbed are key parameters that require investigation. They are largely affected by the loading path complexity, applied strain rate and their interaction. The results showed that the higher the biaxial loading complexity provided by the ACTP, the greater the interaction between the loading complexity and the strain rate, and the greater the energy absorbed by the structures. Changes in local deformation mechanisms induced by the loading complexity thus lead to the energy absorbed enhancement. The latter was higher than 100%, in favor of the most complicated loading path (i.e., Biaxial-60°) compared to the classical uniaxial case for an axial deflection of 20 mm. Simple mathematical equations were proposed predicting the Pm of buckled tubes. These equations can describe the tubes’ behavior fairly well.

A model is developed to describe the grain size effect on elastoplastic behavior of ultrafine grained (ufg) and nanocrystalline (nc) materials using a self-consistent approach. The grain size effect is modeled using two different length scales, the microscale (crystallographic slip system) and the mesoscale (granular level via the grain/matrix interaction law). The difference between the new extension and that previously proposed in Abdul-Latif et al., (2009) is based on the fact that the current extension describes not only the ufg materials with grain size diameter (d) range of (100–1,000nm), but also the nc materials having a range of diameters of (limit value-100 nm) which is defined by a lower slope of the linear Hall-Petch relation compared to the ufg regime. Note that such a limit value (lv) varies between about 15 nm and 30 nm. As a model limitation, the nc metals with grain sizes below lv which behave in the case of copper (lv = 25 nm) either as a plateau or as a decrease of the yield strength cannot be described by the model. In this extension, the grain-boundary attribution is assumed to be globally and implicitly described particularly with further grain refinement (i.e., nc materials). The used self-consistent scheme deals with a non-incremental inclusion/matrix interaction law of softened nature. It describes the non-linear elastic-plastic behavior of fcc polycrystals. The overall kinematic hardening effect can be naturally produced by the interaction law. Within the framework of small strain hypothesis, the elastic isotropic behavior is defined at the granular level. The heterogeneous inelastic deformation is locally determined using the slip theory. The model describes fairly well the effect of grain size on the strain-stress responses of copper and nickel.

International audience; Rubber modified epoxy based composites were designed by low cost production methods. Basically, clean and recycled materials were used to provide a solution for manufacturing of lightweight, cost efficient composites in industrial applications such as automotive and aeronautical engineering. In the present study four different compositions have been developed and characterized for their potential usage as structural materials. The matrix was prepared by treatment of epoxy with 10% recycled rubber. Nano-magnetic iron oxide, Fe3O4, was added to the matrix as reinforcement elements in different percentages. Nickel and aluminium were also add as auxiliary additional elements. Measurements of magnetic permeability and dielectrically properties have been carried out for electronic devise applications basically in aeronautical engineering. Dynamic Scanning Calorimeter (DSC) and Dynamic Mechanical Analysis (DMA) were carried out to determine thermo-mechanical properties. Static tests have been carried out by 3-point bending (3PB) tests for mechanical characterization. Furthermore, creep and wear behaviour of these compositions were evaluated by means of nanoindentation tests to analyze time dependent behaviour of these composites. Macro scratch tests were made in very high cycle test conditions for their measurements in long time resistance. Microstructural and fracture surface analyses have been carried out on the scanning electron microscopy (SEM).All of the experiments; scanning electron microscopy, nanoindentation, static (3PB), test results expose a combined effect of toughening mechanisms high strength and ductile, lightweight and low-cost composites based on the rubber modified epoxy composites reinforced with nano magnetic iron oxide and auxiliary fine nickel and nano aluminium powders.

International audience; To tackle the lack of efficiency of passive sound absorbing treatments in the low frequency range, a specific arrangement of a poroelastic material is proposed. Compared with the usual uniform layout, giving a lamella network structure to a material provides additional sound absorption below the quarter wavelength resonance frequency at oblique incidence. This is demonstrated experimentally on a sample made of melamine foam lamellas. A numerical approach that incorporates geometric periodicity highlights the mechanisms involved in this additional dissipation, achieved by combining structural and viscous dissi-pation within the lamellas. The shear and bending resonances of the lamellas can be excited at oblique incidence. The frequency of the shear resonance is related to the thickness of the sample, whereas the bending resonance is also a function of the width of the lamellas. These simple dimensional parameters allow adjustable tuning of the associated frequencies at which additional sound absorption can be obtained.

In this paper, a hierarchical control for flexible operation of a microgrid is proposed. The structure of the hierarchical control consists of inner, primary and secondary levels. The inner control is used to regulate the output voltage of the inverter which is commonly referred as zero-level. The primary control based on the universal droop control which we improve it to handle both operation modes. It is used to share the active and reactive power accurately with regardless of the output impedance of the inverters. The secondary control compensates the deviation of the microgrid voltage caused by the primary control as well as synchronizes the microgrid voltage with the grid for a smooth transition. Thus, the microgrid can operate either in grid-connected or in islanded mode by using the same control scheme. The small-signal stability of the ameliorated universal droop control is analyzed for both modes, and other levels of control are modeled. Moreover, a technique based on meta-heuristic optimization to design the hierarchical control parameters optimally is introduced. Finally, the simulation was performed on a microgrid that has three voltage source inverters (VSIs) connected in parallel and a local nonlinear load. The results demonstrate the disturbance rejection performance and the flexibility of the proposed control scheme.

International audience; The aim of this paper is to describe the development of a reduced order model for modal analysis in a design context. The design process of most industrial systems is based on the re-utilization of certain components. Here, we propose a reduction method involving component eigenmodes to recover the modal behaviour of an assembled structure. The contribution of this work is that it uses component eigenmodes to build an interface reduction basis. Lastly, the reduction methodology proposed is compared to the Craig and Bampton method by applying it to two case studies of which one is an industrial model of an open rotor blade.

International audience; Predicting the obsolescence risk of components is an important challenge in system life-cycle management to improve its durability. The obsolescence degree measures the obsolescence occurrence risk. Thus, it expresses the probability that an entity will become obsolete within a given time horizon. Some mathematical techniques have already been proposed to deal with this problem. Recent studies have also shown that machine learning methods can be an effective way to improve prediction capability. However, these two classes of techniques assess the obsolescence degree by a scalar at observation time. This does not permit the projection of its possible evolution over time. This paper proposes a new approach based on probability distribution to model the obsolescence degree as a function of time. Based on sales data, the obsolescence degree is modeled as a function of time, and the remaining time-to-obsolescence is inferred. The proposed approach is tested in the prediction of smartphones’ obsolescence. This study's results are then analyzed while proposing future work to be carried out to increase the approach's applicability.

Dense colloidal suspensions can propagate and absorb large mechanical stresses, including impacts and shocks. The wave transport stems from the delicate interplay between the spatial arrangement of the structural units and solvent-mediated effects. For dynamic microscopic systems, elastic deformations of the colloids are usually disregarded due to the damping imposed by the surrounding fluid. Here, we study the propagation of localized mechanical pulses in aqueous monolayers of micron-sized particles of controlled microstructure. We generate extreme localized deformation rates by exciting a target particle via pulsed-laser ablation. In crystalline monolayers, stress propagation fronts take place, where fast-moving particles (V approximately a few meters per second) are aligned along the symmetry axes of the lattice. Conversely, more viscous solvents and disordered structures lead to faster and isotropic energy absorption. Our results demonstrate the accessibility of a regime where elastic collisions also become relevant for suspensions of microscopic particles, behaving as “billiard balls” in a liquid, in analogy with regular packings of macroscopic spheres. We furthermore quantify the scattering of an impact as a function of the local structural disorder., Proceedings of the National Academy of Sciences of the United States of America, 114 (46), ISSN:0027-8424, ISSN:1091-6490

We use hydrodynamical simulations of a Cartwheel-like ring galaxy, modelled as a nearly head-on collision of a small companion with a larger disc galaxy, to probe the evolution of the gaseous structures and flows, and to explore the physical conditions setting the star formation activity. Star formation is first quenched by tides as the companion approaches, before being enhanced shortly after the collision. The ring ploughs the disc material as it radially extends, and almost simultaneously depletes its stellar and gaseous reservoir into the central region, through the spokes, and finally dissolve 200 Myr after the collision. Most of star formation first occurs in the ring before this activity is transferred to the spokes and then the nucleus. We thus propose that the location of star formation traces the dynamical stage of ring galaxies, and could help constrain their star formation histories. The ring hosts tidal compression associated with strong turbulence. This compression yields an azimuthal asymmetry, with maxima reached in the side furthest away from the nucleus, which matches the star formation activity distribution in our models and in observed ring systems. The interaction triggers the formation of star clusters significantly more massive than before the collision, but less numerous than in more classical galaxy interactions. The peculiar geometry of Cartwheel-like objects thus yields a star (cluster) formation activity comparable to other interacting objects, but with notable second order differences in the nature of turbulence, the enhancement of the star formation rate, and the number of massive clusters formed., Comment: Accepted for publication in MNRAS

International audience; The key of successful industry is to satisfy the customer requirements at the perfect delay with improved quality and cheaper price. In this context, Digital Factory is known to test and validate the couple product-production system during the product development process, with the usage of production system simulations. Therefore, we can use an information system to integrate and manage all information related to product, process and simulation in this context. But with this huge amount of information, an actor of product development process may be confused about making a good decision at this particular stage. Thus, there is a lack of knowledge capitalization and sharing between product development process actors. On the basis of previous research works that contribute to the definition of a Digital Factory information system, we propose a new module, named KSim, dedicated to the capitalization and management of knowledge and experiences coming from previous projects in the Digital Factory context.

This paper presents the basic concepts of a systemic theory of interaction between non-deterministic open dynamics with varying temporalities, which includes three stages: the definition of these dynamics as lax-functors, the notion of interaction -- which uses some notions of requests, synchronizations and social modes (privacy) -- and finally the generation of open global dynamics. Some connectivity structures of an interaction are defined, but the other aspects of dynamical connectivity are left to further work., Comment: Cahiers de Topologie et G{\'e}om{\'e}trie diff{\'e}rentielles cat{\'e}goriques, In press, 2020, LXI (4)

International audience; Poroelastic materials are widely used for acoustic treatments due to their efficient sound absorption. Granular materials present also interesting properties according to wave propagation and attenuation. In this work, we study the properties of poroelastic spheres made of polymer foam. The objective is to determine the contact stiffness between a poroelastic sphere and a rigid plane, with a view to homogenize a poroelastic granular material for sound propagation. First, we present experimental results obtained with poroelastic half-spheres, made of same materials but different radii, subjected to a quasistatic strain by a rigid plane. The results show two regimes: a nonlinear Hertzian regime at high strain, which is radius-dependent, preceded by a regime common to all samples at low strain, which relies on the features of the surface. The limit between the two regimes is further studied by a numerical approach using a finite element model of a representative volume. The poroelastic grain is modeled by Kelvin cells within Abaqus software and takes into account the geometrical non-linearity during the deformation.

International audience; For applications dealing with dissipative acoustic waveguides strong modal attenuation are often achieved close to exceptional points (EP). These EP correspond to a particular tuning of certain design parameters which render the associated eigenvalue problem degenerate where both eigenvalues, i.e. the wavenumber, and eigenvectors of a pair of guided modes coalesce. These non-Hermitian degeneracies have raised considerable attention in the scientific community as these can have a great impact in a variety of physical problems. Here, a new algorithm is proposed to quickly explore the parametric space and to locate EPs. The method requires the computation of successive derivatives of two selected eigenpairs with respect to the parameter so that, after recombination, regular functions can be constructed. This algebraic manipulation permits the EP localization, using standard root-finding algorithms and the computation of the associated Puiseux series up to an arbitrary order, useful to follow modal branches. Examples related to the acousic propagation in straight ducts with absorbing walls and in periodic guiding structures are given to illustrate the versatility of the proposed method and its ability to handle large size matrices arising from finite element discretization techniques.

BackgroundThe surgical success of cementless implants is determined by the evolution of the biomechanical properties of the bone–implant interface (BII). One difficulty to model the biomechanical behavior of the BII comes from the implant surface roughness and from the partial contact between bone tissue and the implant. The determination of the constitutive law of the BII would be of interest in the context of implant finite element (FE) modeling to take into account the imperfect characteristics of the BII. The aim of the present study is to determine an effective contact stiffness$$\left( {K_{c}^{\text{FEM}} } \right)$$KcFEMof an osseointegrated BII accounting for its micromechanical features such as surface roughness, bone–implant contact ratio (BIC) and periprosthetic bone properties. To do so, a 2D FE model of the BII under normal contact conditions was developed and was used to determine the behavior of$$K_{c}^{\text{FEM}}$$KcFEM.ResultsThe model is validated by comparison with three analytical schemes based on micromechanical homogenization including two Lekesiz’s models (considering interacting and non-interacting micro-cracks) and a Kachanov’s model.$$K_{c}^{\text{FEM}}$$KcFEMis found to be comprised between 1013and 1015 N/m3according to the properties of the BII.$$K_{c}^{\text{FEM}}$$KcFEMis shown to increase nonlinearly as a function of the BIC and to decrease as a function of the roughness amplitude for high BIC values (above around 20%). Moreover,$$K_{c}^{\text{FEM}}$$KcFEMdecreases as a function of the roughness wavelength and increases linearly as a function of the Young’s modulus of periprosthetic bone tissue.ConclusionsThese results open new paths in implant biomechanical modeling since this model may be used in future macroscopic finite element models modeling the bone–implant system to replace perfectly rigid BII conditions.

International audience

The growing penetration of mechanical engineering through information technology has led to considerable advantages. The resulting discipline that expresses the tight integration of mechanics, electronics, control and software engineering is called mechatronics. Therefore, designing mechatronic systems is a complex as well as an interdisciplinary task. Added to that, developing a new mechatronic product takes a lot of time due to the iterative exchange loops between the designers, the manufacturing engineers and other specialists, which subsequently increase the development cost. Hence, continuous and effective communication and cooperation between developers from various fields during the entire development process is necessary. In this context, we propose an approach based on the integration of the set-based concurrent engineering principles with the system engineering methodology for the design of complex mechatronic systems, taking into consideration the production system constraints in the early design stages. The goal of this approach is to reduce the iterative exchange loops between different participants, which in turn minimize the cost and time required to develop a mechatronic product.

Nanoparticulates and nanofibres are good candidates to be considered as reinforcements in the design of new multiferroic composites processed by powder metallurgy. As would be expected in a...

This work deals with the active control of the vibrations of mechanical structures incorporating magnetorheological elastomer. The damping coefficient and shear modulus of the elastomer increase when exposed to a magnetic field. Compared with the vibration control where the elastomer is permanently exposed to a magnetic field, the control of this process through time reduces vibrations more effectively. The experimental study for the vibrations of a sandwich beam filled with an elastomer is conducted, followed by a numerical study using the Abaqus code. The vibration damping is found to be dependent on the loading rate of micro-size ferromagnetic particles in the elastomer.

The aim of this paper is to describe a procedure for computing the dynamic stiffness matrix relative to the in-plane effect for an orthotropic rectangular plate. The dynamic stiffness matrix is calculated for free edge boundary conditions. The formulation is based on strong solutions for the equations of motion for an orthotropic plate obtained with the Levy series and a Gorman decomposition of the free boundary conditions. The results obtained for the in-plane harmonic response are validated by the Finite Element Method.

International audience; In this paper a methodology to model a GFRP adhesive connections by using an imperfect soft interface model is presented. The model based on Kachanov's theory considered a cracked thin adhesive. Within this framework, the mechanical properties and the initial damage (diffuse initial cracks) of the adhesive layer has been experimentally evaluated. With a modified Arcan system, static tests were performed on adhesively bonded assemblies in tensile and shear solicitation mode considering three different adhesive thicknesses. The experimental results highlighted how the thickness of adhesive influences the mechanical strength and stiffness of the bonded connection. CT-scans were performed to measure the porosity rate in the adhesive layer. Furthermore, the excellent comparison of numerical and experimental data of an adhesive GFRP bonded connections allow us to consider the imperfect soft interface model proposed as highly competitive to evaluate complex structure performance in civil engineering context. A parametric analysis has been proposed to provide a formula able to describe the full response of the structure at varying adhesive property.

A numerical algorithm is proposed to explore in a systematic way the trajectories of the eigenvalues of non-Hermitian matrices in the parametric space and exploit this in order to find the locations of defective eigenvalues in the complex plane. These non-Hermitian degeneracies also called exceptional points (EP) have raised considerable attention in the scientific community as these can have a great impact in a variety of physical problems. The method requires the computation of successive derivatives of two selected eigenvalues with respect to the parameter so that, after recombination, regular functions can be constructed. This algebraic manipulation permits the localization of exceptional points (EP), using standard root-finding algorithms and the computation of the associated Puiseux series up to an arbitrary order. This representation, which is associated with the topological structure of Riemann surfaces allows to efficiently approximate the selected pair in a certain neighbourhood of the EP. Practical applications dealing with guided acoustic waves propagating in straight ducts with absorbing walls and in periodic guiding structures are given to illustrate the versatility of the proposed method and its ability to handle large size matrices arising from finite element discretization techniques. The fact that EPs are associated with optimal dissipative treatments in the sense that they should provide best modal attenuation is also discussed., Comment: Fix typo in Eq. (17), add EasterEig library url, few other enhancements

In this chapter we first recall a collection of converse Lyapunov–Krasovskii theorems for uncertain linear retarded systems. The originality of these theorems resides in the weakly-degenerate conditions required on the Lyapunov–Krasovskii functionals. Thanks to these theorems, sufficient conditions for the stability of interconnected uncertain linear retarded systems are given.

International audience; Predictive simulations of assembled structures raises some computational challenges for usual industrial structures. It is indeed necessary to deal with non-linear phenomena, such as contact or friction, and to consider sources of uncertainties mainly responsible for the deviation between the effective behaviour of the structure and results from deterministic simulations. Each of these two features of assembled structures requires intensive computational resources and the significant number of joints of actual structures increases even more the computational cost. In order to address such problems, this work aims to provide a pragmatic approach to robustly characterize the vibrational behaviour of light assembled structures considering the variability of the parameters of the joints. All the uncertainties of the whole problem are assumed to be associated to the joint interfaces. First, a nominal model of a joint consistent with the studied structure is identified using experimental data. Then a stochastic model of a joint is defined by considering the mechanical design variables of the nominal model as random variables. Based on an approximation of the maximum likelihood principle, the parameters of this stochastic model of joint are identified. A straightforward non-intrusive strategy referred to as the Stochastic Model Reduction (SMR) approach is used in the identification procedure of the stochastic model of the joint. The ease of implementation and the efficiency of the SMR approach justify this choice. The proposed approach is applied to an academic structure which is representative of light assembled structures: a three beam bolted frame. A stochastic model of joint characterized by its stiffness is thus implemented for each elementary joint of this frame. It allows us to characterize the variability of the vibrational behaviour of the frame taking into account the variability of each joint. Finally the comparison of the predicted stochastic response with the experimental behaviour of the structure shows that the proposed approach allows to tackle the variability of the actual structure. The proposed approach has been developped in the purpose of industrial applications. Based on a pragmatic modeling of the joint, a non-intrusive numerical tool and a stochastic modeling, the whole strategy could be indeed easily implemented on more complex industrial assemblies.

Titanium alloys have been widely used in industries, especially aerospace, energy and medical industries, due to their good mechanical and chemical properties. However, titanium alloys are typically difficult-to-cut materials. That is why, in industries we are using many process to cut this alloys. In fact, several studies have made a comparisons between the various machining processes currently used in industries to cut Titanium alloys.

This paper discusses damping effect of the reinforcements on the epoxy modified (10, 20 and 30 wt. %) devulcanized recycled rubber based composites. Within this study, the influence of Boron, γ-alumina and hollow glass microspheres (HGM) added in the matrix as the reinforcement elements were examined. As well known, devulcanization process is an efficient method of micronized rubber that can be used as useful products in a highly valued form. In this study, a combined process (chemical treatment + microwave) was used in order to modify the structure of the scrap recycled rubber. To characterize toughening and impact behaviour, quasi static 3P bending tests and choc tests were used for obtaining the principal values KIc and GIc and also damping capacity due to the reinforcement particles. Additionally, Shore-D hardness tests were measured. Scanning Electronic microscopy (SEM) was used to check dispersion quality and fracture surfaces, in scanning mode.

This work present a comprehensive study on the effect and optimization of machining parameters on the kerf (cutting width) and material removal rate (MRR) in wire electrical discharge machining (WEDM) process by using the response surface methodology (RSM) and Taguchi method. The experimental studies were conducted under varying parameters. The main input parameters on this model are the cutting parameters such us pulse on time (Ton), servo voltage (U), Speed of advance or feed rate (S) and injection pressure or flushing pressure (P). Recycled Titanium based composite (an alloy Ti17) was used for machining operations and the combined effects of cutting parameters on the material removal MRR rate and kerf were investigated while using the analysis of variance ANOVA. Mathematical models were used for the objective of minimum kerf and maximum MRR, Cut edge surface analysis was carried out using an optic microscope and Scanning Electron Microscope (SEM) to evaluate the kerf.

Designing mechatronic systems implies collaborative work with shared parameters between contributors from different domains. Moreover, each domain needs to capitalize knowledge (e.g. design rules) in order not to reinvent specific calculation or simulation processes. In this paper, it is explained how students have been implied in a collaborative design project dealing with an aeronautic actuator, namely an EMA (ElectroMechanical Actuator) for aileron actuation. Comparing three candidate kinematic architectures regarding the initial set of requirements, the project articulates modeling and simulation with Modelica language, the selection of relevant COTS components and their integration into a 3D mock-up within a wing and aileron assembly. In order to share relevant system and components parameters between design activities, KARREN tool is evaluated and configured for this project thanks to a preliminary systems engineering study to minimize the number of needed iterations to eventually converge on appropriate architectural solutions and their evaluation and comparison.