Mohamed Guessasma

• Professor
• Institut Supérieur de Sciences Et Techniques - INSSET at University of Picardie Jules Verne

Thermal Barrier Coatings (TBCs) are advanced multilayer structures designed to provide thermal insulation for Ni-based superalloy components used in gas turbine blades. These coatings enhance the performance of the components by enabling them to withstand higher temperatures (∼ 1100 ° C). However, the complex microstructure of TBCs, combined with h...

This contribution deals with the development of a numerical approach based on discrete element method to study the hygrothermal behaviour of conventional and composite materials. For this purpose, we consider the context of magnesium aluminate and polyamide 6 reinforced with 30% of short glass fibre respectively. A coupled hygrothermal model based...

This paper discusses the development of a numerical approach based on the Discrete Element Method (DEM) to simulate the interfacial debonding in Short Fibre Reinforced Composites (SFRC). For that purpose, we consider a hybrid lattice-particle approach based on a cohesive beam model. Already used to study composite materials, we aim to extend this c...

Composite materials have been widely used across industry sectors. However, they are characterized by a variability of thermal conductivity with the architecture and manufacturing processes. Hence, thermal transfer in composite materials requires an improved fundamental understanding. From numerical purposes, the Finite Element Method (FEM) seems a...

Composite materials, due to their superior properties and low density, are desirable in applications where weight reduction is crucial. PA6/GF30 (Polyamide 6 reinforced with 30% of glass fibers) is one of those materials used in the automotive sector. It represents an alternative to metal structures as part of the engine compartment and interior eq...

The present contribution deals with an investigation of the halo approach to simulate cracks initiation and propagation in homogeneous and heterogeneous materials by Discrete Element Method using the hybrid lattice-particle model. Recent developments highlighted that the halo, which can be described as a spherical interaction domain of controlled s...

In this paper we investigate the elastohydrodynamic (EHD) lubrication in ball bearings by means of a digital twin. Based on an original description involving the discrete element method (DEM), the digital twin integrates all the components of ball bearings and enables realistic behavior under mechanical loading and kinematic conditions. In order to...

Powder solids are regularly faced to the problem of caking during their periods of storage and/or transport. Caking is involved by attractive forces acting between particles under environmental conditions over time. Given the complexity of phenomena occurring simultaneously at particle's scale on the one hand, and the heterogeneity of the system, o...

This paper presents a multi-scale modelling approach to describe the mechanical behaviour of caked powders as an aid to properly design and analyse the results of laboratory caking tests to assess the propensity of powders to cake. This approach is based on the integration of particle-particle interactions due to liquid or solid bridges over the to...

The transport sector, particularly the automotive industry, is in a deep change as regards the environmental and social challenges it poses. The concept of sustainable mobility has become a m ajor issue for everyone, car manufacturers as well as economic actors. Recent European Union legislat ion s restrict pollutant emissions of light vehicules. A...

The paper aims to investigate the suitability of a 3D discrete element method to simulate the thermal-induced damage in composite materials using a cohesive beam model. First, we aim to predict the elastic behavior of continuous material in the case of a homogeneous medium. For that purpose, mechanical tests are performed on a representative patter...

La présente contribution s’inscrit dans une démarche visant à établir un modèle numérique permettant de prédire le comportement mécanique et l’endommagement à long terme d’un matériau composite utilisé dans le secteur automobile, le PA6/GF30. Dans l’optique de proposer une approche à la fois fiable et suffisamment flexible pour intégrer l’ensemble des...

Discrete element method (DEM) is an interesting alternative to classical approaches as the finite element method (FEM) to simulate homogeneous and heterogeneous materials. Indeed, although DEM was initially developed to simulate granular systems in motion, it also enables to model a continuous medium with the help of a dense granular packing in whi...

Modélisation 3D des roulements à billes

La présente contribution vise à développer la Méthode des Eléments Discrets (MED) basée sur le modèle cohésif de type poutre pour la prédiction du comportement mécanique de matériaux composites fibreux. Ce travail est abordé par le biais du code par éléments discrets MULTICOR3D++ qui permet la modélisation et la simulation mécanique des matériaux h...

L’objectif de la présente contribution est de développer une approche permettant de contrôler le niveau de dispersion du champ de contrainte locale dans la simulation 3D par la Méthode des Éléments Discrets (MED), basée sur le modèle cohésif de type poutre. L’approche introduite, que nous avons nommé Halo, permet de lier directement le niveau de di...

This work deals with caking behaviour of lactose monohydrate powders containing small amounts of amorphous lactose. The objective was to elucidate the relation between the caking ability of powder mixtures and the crystallisation behaviour of amorphous lactose. Binary mixtures consisting of amorphous lactose and α-lactose monohydrate were prepared...

In the recent years, the reduction of vehicles' weight has become a major issue for the green growth of the automotive industry. This approach will necessarily appeal to the progress and the innovation in the field of structural lightening. PA6/GF30 is an alternative to metal structures in this area with its mechanical performances. However, this m...

The present paper is dedicated to an application of the discrete element method (DEM) to study heat transfer by conduction in continuous and heterogeneous media. Our objectives are threefold. First, we aim to set up an original process to generate a Voronoi tessellation based on a granular assembly. This efficiently provides suitable areas of trans...

The present contribution is dedicated to a coupling method mixing finite and discrete elements to simulate thermally induced stresses and local damage in composites. Investigations are focused on ceramic-metal materials which are characterized by a strong difference of properties and a coefficient of thermal expansion mismatch. Typically, thermal r...

In this work, a Discrete Element Method (DEM)-based numerical model has been developed in C++ program, which enables to simulate the crack propagation of plasma-sprayed Al2O3 coatings thus enabling to predict their failure. DEM-based approach is combined with the image analysis procedure applied on two-dimensional (2D) cross-section images of as-sp...

This paper deals with an efficient 3D modelling of a radial ball bearing to predict the operating lubrication regime under mechanical loading and mounting conditions by using the Discrete Element Method (DEM). Due to the relevance of such an approach, especially for multicontact systems, the lubrication regime associated with specific operating con...

The present paper deals with an original 2D modeling of mechanical state of ball bearings in dynamic mode using the Discrete Element Method (DEM). An electromechanical coupling is introduced to extract an electrical and measurable response of a bearing in operation, for monitoring and diagnostic purposes. Recent research activities at the LTI have...

The microstructure of composites is often complex and exhibits local defects such as void areas and interfacial debonding. Thus, it is difficult to predict their mechanical behavior using classical continuous methods. The Discrete Element Method (DEM) is a good alternative because it naturally takes into account discontinuities. However, in DEM sim...

This chapter presents the description of physical phenomena in the context of the modeling of the contact interface behavior based on discrete element method (DEM) and coupled DEM–finite element method (DEM–FEM) approach. Our interest in this area, which is related to several engineering applications where the contact interface plays a significant...

This chapter presents the description of physical phenomena in the context of the modeling of the contact interface behavior based on discrete element method (DEM) and DEM–finite element method (DEM–FEM) coupled approach. Our interest in this area, which is related to several engineering applications where the contact interface plays a significant...

The present contribution deals with a discrete element method to simulate thermal-induced damage in 2D composite materials. We consider a hybrid particulate-lattice model based on the equivalence between a granular system and a network of cohesive beam elements. This choice is mainly motivated by previous papers exhibiting its ability to model hete...

The present work is dedicated to the mechanical simulation of continuous and heterogeneous media using a cohesive discrete element method. In this approach, an equivalent continuous model based on granular packings composed of disks in 2D and spheres in 3D is considered. The cohesion is introduced at the scale of particles by replacing the contact...

This work deals with the modeling of the mechanical and kinematic state of a ball bearing using Discrete Elements Method (DEM). An electromechanical coupling is introduced to extract an electrical and measurable response of a bearing in operation, for monitoring and diagnostic purposes. Recent research activities at the LTI have helped us to measur...

This paper presents an original approach using Discrete Element Method (DEM) for predicting the mechanical behavior of a bearing considering rigid and elastic housing. The ability of DEM to describe accurately the mechanical state of a bearinghas been established by means of a comparison with FEM, of mechanical stresses and load distributions in a...

We have developped an original 2D modeling of bearings by Discrete Element Method (DEM). The mechanical behavior and the dynamic of a bearing is well reproduced. An electromechanical coupling is introduced to provide monitoring solutions. In practice, the mechanical state in real-time is usually unknown and existing numerical methods are restricted...

La présente contribution vise à étudier la capacité de la Méthode des Éléments Discrets (MED) à simuler l'initiation et la propagation de fissures en milieu hétérogène. Nous considérons le modèle de poutre cohésive lequel modélise de manière naturelle des motifs de rupture complexes. Dans une première approche, nous étudions le cas d'un test d'inde...

Ce travail allie une approche par la Méthode des Eléments Discrets (MED) qui permet de modéliser entièrement le roulement avec une formulation électromécanique de façon à déduire une réponse électrique du roulement en fonctionnement à des fins de surveillance et de diagnostic. Des activités de recherche récentes au sein du LTI ont aidé à simuler, m...

This work deals with numerical simulation of powder caking process caused by capillary condensation phenomenon. Caking consists in unwanted agglomeration of powder particles. This process is often irreversible and not easy to predict. To reproduce mechanism involved by caking phenomenon we have used the Discrete Elements Method (DEM). In the presen...

The present paper investigates the suitability of a Discrete Element Method (DEM) to simulate cracks initiation and propagation in heterogeneous media. We focus our studies on the cohesive hybrid-particulate model in which the continuous medium is modeled using a cohesive beam model. Previous works exhibited the ability of such an approach to simul...

This work deals with the role of capillary condensation phenomenon on the caking behavior of powders. A theoretical basis is established to provide a quantitative description of the behavior of powders subjected to humidification. This approach is based on the integration of water condensation and liquid bridge formation within binary contacts in r...

Rolling bearings are one of the most important and frequently components encountered in domestic and industrial rotating machines. Statistical studies show that these bearings are considered as critical mechanical parts which represent between 40% and 50% of malfunction in rotating machineries. We performed an electrical monitoring of a bearing and...

Despite the significant progress made towards the understanding of flame propagation mechanisms in dust-air mixtures, dust explosions still have a frequent occurrence and their danger presents a continuous threat to industries that produce, use and treat solid powders and dusts of combustible materials. In fact, many physical aspects are still need...

This paper aims to validate the discrete element method (DEM) model of sintering. In situ X-ray microto- mography experiments have been carried out at the ESRF to follow the sintering of NaCl powder, the properties of which are close to the DEM model assumptions. DEM simulations are then run using an improved implicit method. The compar- ison betwe...

Modélisation discrète du transfert électrique dans les matériaux granulaires

La méthode des éléments discrets s’avère une approche adaptée pour la simulation du comportement mécanique de milieux continus homogènes pour lesquels des phénomènes locaux tels que l’endommagement et la fissuration interviennent. Dans cette communication, nous nous intéressons aux milieux continus hétérogènes pour lequel un travail important de va...

e travail allie une approche par la Méthode des Eléments Discrets (MED) qui permet de modéliser entièrement le roulement avec une formulation électromécanique qui permet d’extraire une mesure électrique du roulement en fonctionnement. Des activités de recherche récentes au sein du LTI ont aidé à simuler et comprendre la réponse électrique d’un syst...

Cette étude a pour ambition de développer un outil numériqu e fiable contribuant à une meilleure compréhension de la transition des phénomènes ph ysiques à différentes échelles. Plus précisé- ment, nous avons mis en place un modèle multi-physiques pour étudier le comportement thermomé- canique de deux corps en contact, entre lesquels est piégé un m...

The paper describes an efficient numerical model for better understanding the influence of the microstructure on the thermal conductivity of heterogeneous media. This is the extension of an approach recently proposed for simulating and evaluating effective thermal conductivities of alumina/Al composites. A C++ code called MultiCAMG, taking into acc...

This project represents a straight continuation of the research activities of the LTI and which helped to simulate and understand the electrical response of multi-contact systems. In order to make further progress in the electrical modeling, the electrical transfer model is applied to the case of bearing operation. The 2D modeling by discrete eleme...

This paper describes a new manufacturing process for producing functionally graded ceramic-metal composites with anisotropic properties for thermal management in automotive engine blocks. These composites are elaborated by producing a porosity gradient within an alumina matrix, subsequently infiltrated by a molten aluminum alloy. The interconnected...

Rolling bearings are one of the most important and frequently encountered components in domestic and industrial rotating machineries. Statistical studies show that these bearings are considered as critical mechanical components which represent between 40% and 50% of malfunction in rotating machineries. This project represents a straight continuatio...

This project represents a straight continuation of the research activities of the LTI and which helped to simulate and understand the electrical response of multi-contact systems. In order to make further progress in the electrical modeling, the electrical transfer model is applied to the case of bearing operation. The 2D modeling by discrete eleme...

Ce travail porte sur la réalisation de capteurs Interdigités (IDT) sur des supports piézoélectriques flexibles. L’enjeu est double puisqu’il s’agit premièrement de disposer de capteurs souples dont la fréquence propre est la plus élevée possible afin de générer des ondes de surface qui donnent la possibilité de caractériser les surfaces des structu...

This paper presents a DEM study of the sintering of bimodal powders. The influence of every type of contact between small-small, large-large and small-large particles on the macroscopic behavior is investigated. A generalized mean strain law that takes into account the contribution of the different contacts was used to compare the theoretical kinet...

The aim of this study is to present an original approach for the simulation of sintering with Discrete Element Method, using a Non Smooth Method called Contact Dynamics. Recently, there have been numerous papers about the simulation of sintering using Discrete Element approaches. Most of these papers use Smooth Dynamics and their results match well...

La caractérisation des revêtements par contrôle non destructif et le suivi de leur évolution en cours d’utilisation est assurée par la mise en place de protocoles spécifiques de suivi des défauts avec comme corollaire la mise en place de capteurs ultrasonores interdigités (IDT) dédiés à cette application. Les nouveaux capteurs réalisés ayant une fo...

This paper investigates the definition of the stress tensor within a granular assembly, when inertial effects are likely to occur. It is shown that the stress tensor can be expressed as a sum of two terms. A first term corresponds to the standard definition of the stress, according to the Love–Weber formula; this term is related to the contact forc...

L'originalité de ce travail repose sur la modélisation par les éléments discrets pour simuler le roulement et sur l'utilisation des mesures électriques pour caractériser les défauts. D'un point de vue numérique, nous proposons d'étudier le transfert des informations mécaniques vers les grandeurs électriques, afin de développer une nouvelle méthode...

Le frittage est un procédé clé dans la fabrication des matériaux céramiques. Différents modèles ont été proposés dans la littérature, à l'échelle du grain ainsi que d'un empilement de particules, avec des hypothèses diverses sur l'évolution géométrique et les modes de diffusion prédominants. Depuis quelques années, plusieurs approches utilisant la...

This article describes a novel technique for manufacturing functionally graded materials with tailored properties for thermal management. These materials are ceramic/metal composites with a gradient microstructure, elaborated by producing a porosity gradient preform made of alumina phase subsequently infiltrated by the molten aluminum alloy (Al) ph...

In this work we propose to study the electrical transfer in metallic granular materials under mechanical loading. A new model of electrical conductance and the associated numerical treatment in the Discrete Element Method (DEM) framework are presented. The approach differs from the Holm’s model by considering several electrical potentials inside a...

Dans ce travail nous nous intéressonsà la modélisation du transfertélectrique dans les milieux gra-nulaires métalliques par une approche discrète. Les travaux expérimentaux ont mis enévidence la complexité du comportementélectrique de ces milieux sous chargement mécanique. Les propriétésélectriques dépendent des interactions entre particules dans l...

In this work we focus on modeling the electrical transfer in granular metal by a discrete approach. The experimental work showed the complexity of the electrical behavior of these media under mechanical loading. The electrical properties depend on the contact forces in case of a perfect electrical contact. A discrete element numerical modeling allo...

A numerical model is proposed for modeling functionally graded materials (FGMs) in which the architecture of the FGMs is obtained from a granular material composed of overlapping spherical particles as skeletal structure. The numerical approach is based on both discrete element method (DEM) and finite element method (FEM). The model is able to simu...

The aim of this study is to numerically identify laws of interfaces between two bodies when this interface is a microstructure composed by grains. This problem has clearly two different scales and requires a specific numerical treatment. The bodies represent the macroscopic scale and the grains are the microscopic scale. In this paper, we propose v...

Many materials which are used in several engineering domains can be considered as multi-contact systems. A realistic modeling of the behavior of such materials can be done only by a discrete approach. This paper deals with the modeling of cohesive multi-contact systems by using a Non Smooth Contact Dynamics (NSCD). Throughout this study, we attempt...

Dans le domaine de la simulation numérique en mécanique et plus généralement des sciences de l'ingénieur, la Méthode des Eléments Finis (MEF) est largement utilisée. Ainsi, tous les logiciels mettant en oeuvre cette méthode proposent des outilsévolués de post-traitement et de visualisation des résultats. Ces outils ont at-teint aujourd'hui une gran...

Heat transfer in particulate beds has an important impact for many industrial processes as well as for the storage of particulate material. This study is aimed at modeling the granular flow and heat transfer between particles during the discharge of a silo. A numerical model based on the detection of contacts and the evolution of heat transfers in...

This study deals with the modelling of the thermomechanical phenomena due to friction effects during granular flow. A two-dimensional model using the discrete element method (DEM) and taking into account the contact detection and heat transfers between grains has been developed. Through this study, we have modelled the heat transfer by conductance...

The aim of this work is a numerical simulation of physical phenomena during the grinding process by using a discrete approach. The Discrete Element Method (DEM) has been used to model the fragmentation and mechanical behaviour of granular packing under compressive forces. Through this study, we show the effect of contact force chains on the stress...

The aim of this study is the modeling of the fragmentation of granular material subjected to compressive loading by using Discrete Element Method (DEM). The proposed model depends mainly on two mechanical aspects which are: the mechanical behavior of the granular material and the yield strength predicting the fragmentation of grains. In order to be...

This article deals with the linear behavior of sandwich structures by using homogenization method for periodic media. An orthotropic layered plate model substituting the three-dimensional (3D) structure is proposed. The use of the equivalent model for an industrial example allows the authors to validate the proposed model and shows also its utility...

This study is aimed at modeling the heat transfers in a multi-contact system. A model based on the detection of contacts and the evolution of heat transfers in particle flow has been developed drawing upon the Discrete Element Method (DEM). Through this work, we also model the heat flows generated by friction and collision. This modeling enables to...

For an industrial purpose, an error estimator in quantities of interest is proposed based on an explicit residual based error estimator. Applications for the estimation of error on mixed-mode stress intensity factors are presented. An adaptive strategy is proposed, based on the concept of mesh optimality. In order to validate this estimator, some n...

Des estimateurs d'erreurs locaux dits en quantités d'intérêt permettent d'obtenir directement l'erreur de discrétisation commise sur une quantité ayant un sens physique, dans une zone définie. On construit un tel estimateur à partir de l'erreur sur la solution du problème primal, celle du problème dual et un estimateur d'erreur basé sur les résidus...