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See detailMicro-macro analysis of steel sheet behaviour in finite element simulations. Application to deep-drawing process.
Duchene, Laurent ULg; Godinas, A.; Cescotto, Serge ULg et al

in Cescotto, Serge (Ed.) Proceedings of the Sixth European Mechanics of Materials Conference (EMMC6) Non Linear Mechanics of Anisotropic Materials (2002, September)

This paper presents a constitutive law based on Taylor’s model implemented in our non-linear finite element code LAGAMINE. The yield locus is only locally described and a particular interpolation method ... [more ▼]

This paper presents a constitutive law based on Taylor’s model implemented in our non-linear finite element code LAGAMINE. The yield locus is only locally described and a particular interpolation method has been developed. This local yield locus model uses a discrete representation of the material’s texture. The interpolation method is presented and a deep-drawing application is simulated in order to show up the influence of the texture evolution during forming processes. [less ▲]

Detailed reference viewed: 37 (5 ULg)
See detailMicro-macro mechanical modeling of bone-implant interface by means of the homogenization theory
Amor, Nadia; Van Cleynenbreugel, Tim; Geris, Liesbet ULg et al

Poster (2006, December)

Detailed reference viewed: 15 (2 ULg)
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See detailA Micro-Macroapproach to Predict Stiction due to Surface Contact in Microelectromechanical Systems
Wu, Ling ULg; Noels, Ludovic ULg; Rochus, Véronique et al

in IEEE/ASME Journal of Microelectromechanical Systems (2011), 20(4), 976-990

Stiction, which results from contact between surfaces, is a major failure mode in micro electro-mechanical systems (MEMS). Indeed microscopic structures tend to adhere to each other when their surfaces ... [more ▼]

Stiction, which results from contact between surfaces, is a major failure mode in micro electro-mechanical systems (MEMS). Indeed microscopic structures tend to adhere to each other when their surfaces enter into contact and when the restoring forces are unable to overcome the interfacial forces. Since incidental contacts cannot be completely excluded and since contacts between moving parts can be part of the normal operation of some types of MEMS, stiction prediction is an important consideration when designing micro and nano-devices. In this paper a micro-macro multi-scale approach is developed in order to predict possible stiction. At the lower scale, the unloading adhesive contact-distance curves of two interacting rough surfaces are established based on a previously presented model [L. Wu et al., J. Appl. Phys. 106, 113502, 2009]. In this model, dry conditions are assumed and only the van der Waals forces as adhesion source are accounted for. The resulting unloading adhesive contact-distance curves are dependant on the material and on surface properties, such as, elastic modulus, surface energy and on the rough surfaces topography parameters; the standard deviation of asperity heights and the asperities density. At the higher scale, a finite element analysis is considered to determine the residual cantilever beam configuration due to the adhesive forces once contact happened. Toward this end, the adhesive contact-distance curve computed previously is integrated on the surface of the finite elements as a contact law. Effects of design parameters can then be studied for given material and surface properties. [less ▲]

Detailed reference viewed: 191 (93 ULg)
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See detailMicro-mechanical analysis of steel sheet behaviour during deep-drawing
Duchene, Laurent ULg; Godinas, A.; Habraken, Anne ULg et al

in Proceedings of the First Asian-Pacific Congress on Computational Mechanics: APCOM 2001 (2001)

Detailed reference viewed: 21 (5 ULg)
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See detailA micro-meso model to predict van der Walls and capillary induced stiction in micro-structures
Hoang Truong, Vinh ULg; Noels, Ludovic ULg; Wu, Ling ULg

Conference (2013, December)

Undesirable stiction in MEMS results from the contact between surfaces and is due to the adhesive van der Waal and/or capillary forces, which become important for micro-structures. In this work, a micro ... [more ▼]

Undesirable stiction in MEMS results from the contact between surfaces and is due to the adhesive van der Waal and/or capillary forces, which become important for micro-structures. In this work, a micro-macro multi-scale approach is developed in order to predict possible stiction in MEMS structures At the lower scale, the unloading adhesive contact-distance curves of two interacting rough surfaces are established based on Maugis’ model extended herein to account simultaneously for the van der Waals and the capillary forces. The resulting unloading adhesive contact-distance curves are dependent on the material and surface properties -such as elastic modulus, surface energy- on the rough surfaces’ topography parameters -the standard deviation of asperities heights and the asperities’ density- and on the humidity level. At the higher scale, a beam finite element analysis is considered to determine the residual configuration due to the adhesive forces once contact happened. Toward this end, the adhesive contact-distance curve computed previously is integrated on the surface of the finite elements as a contact law. [less ▲]

Detailed reference viewed: 42 (14 ULg)
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See detailA micro-meso-model of intra-laminar fracture in fiber-reinforced composites based on a Discontinuous Galerkin/Cohesive Zone Method
Wu, Ling ULg; Tjahjanto, Denny; Becker, Gauthier ULg et al

in Engineering Fracture Mechanics (2013), 104

The recently developed hybrid discontinuous Galerkin/extrinsic cohesive law framework is extended to the study of intra{laminar fracture of composite materials. Toward this end, micro-volumes of di erent ... [more ▼]

The recently developed hybrid discontinuous Galerkin/extrinsic cohesive law framework is extended to the study of intra{laminar fracture of composite materials. Toward this end, micro-volumes of di erent sizes are studied. The method captures the debonding process, which is herein proposed to be assimilated to a damaging process, before the strain softening onset, and the density of dissipated energy resulting from the damage (debonding) remains the same for the di erent studied cell sizes. Finally, during the strain softening phase a micro{crack initiates and propagates in agreement with experimental observations. We thus extract a resulting mesoscale cohesive law, which is independent on the cell sizes, using literature methods. [less ▲]

Detailed reference viewed: 104 (31 ULg)
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See detailA micro-model of the intra-laminar fracture in fiber-reinforced composites based on a discontinuous Galerkin/extrinsic cohesive law method
Wu, Ling ULg; Tjahjanto, Denny; Makradi, Ahmed et al

Conference (2013, June)

The hybrid discontinuous Galerkin (DG)/extrinsic cohesive law (ECL) method was recently proposed [1] to circumvent the drawbacks of the cohesive element methods. With the DG/ECL method, prior to fracture ... [more ▼]

The hybrid discontinuous Galerkin (DG)/extrinsic cohesive law (ECL) method was recently proposed [1] to circumvent the drawbacks of the cohesive element methods. With the DG/ECL method, prior to fracture, the flux and stabilization terms arising from the DG formulation at interelement boundaries are enforced via interface elements in a way that guarantees consistency and stability, contrarily to traditional extrinsic cohesive zone methods. At the onset of fracture, the traction–separation law (TSL) governing the fracture process becomes operative without the need to modify the mesh topology since the cohesive elements required to integrate the TSL are already present. This DG/ECL method has been shown to be an efficient numerical framework that can easily be implement in parallel with excellent scalability properties to model fragmentation, dynamic crack propagation in brittle and small-scale yielding materials, both for 3D problems and for thin structures [1, 2]. In this work, following the developments in [3], the DG/ECL method is extended to the study of composite materials failures at the micro-scale. The method is applied to study the transverse traction of composite materials in characteristic micro-volumes of different sizes. The method captures the debonding process, assimilated to a damaging process before the strain softening onset. It is shown that the density of dissipated energy resulting from the damage (debonding) remains the same for the different studied cell sizes. During the strain softening phase, a micro-crack initiates and propagates, in agreement with experimental observations. After strain softening onset, the extracted macroscale cohesive law, obtained by the method proposed in [4], is ultimately shown to converge for the different cell sizes. The predicted behaviors are then compared to experimental results obtained from laminate tests, and are found to be in good agreement. [less ▲]

Detailed reference viewed: 33 (2 ULg)
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See detailMicro-modeling of retirement in Belgium
Dellis, A.; Desmet, R.; Jousten, Alain ULg et al

Report (2002)

The present paper studies the retirement incentives for elderly people in Belgium. We model the incentive structure built into the various public retirement and early retirement systems. First, we compute ... [more ▼]

The present paper studies the retirement incentives for elderly people in Belgium. We model the incentive structure built into the various public retirement and early retirement systems. First, we compute indicators of benefit entitlement such as the social security wealth. Then, we use three different incentive measures based on the notion of social security wealth. In a third step, we perform an empirical estimation of micro-econometric probit and option value models. From our exceptionally rich and broad database, we are able to compute rather accurate measures of all individuals’ pension wealth, as well as of the implicit tax rates the elderly workers face in case of delayed retirement. We find strong evidence of social security based financial incentives inducing most workers to retire at the earliest possible stage. Finally, we use the derived parameter estimates from the probit models to simulate the responses to various policy changes. [less ▲]

Detailed reference viewed: 14 (5 ULg)
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See detailMicro-modelling of retirement incentives in Belgium
Jousten, Alain ULg; Dellis, A.; Desmet, R. et al

in Gruber, J.; Wise, D. (Eds.) Social Security Programs and Retirement around the World: Micro Estimation (2004)

Detailed reference viewed: 19 (8 ULg)
Peer Reviewed
See detailMicro-organismes pathogènes et viande : la traçabilité alliée de la sécurité.
Daube, Georges ULg

in Extrait du Bulletin de la Société Royale des Sciences de Liège (2001), 1

Detailed reference viewed: 22 (0 ULg)
Peer Reviewed
See detailMicro-phonochirurgie assistée au laser CO2 des lésions bénignes des cordes vocales
Remacle, Marc; Giovanni, Antoine; Lawson, George et al

in Cahiers d'Oto-rhino-laryngologie, de Chirurgie Cervico-faciale et d'Audiophonologie (Les) (2000), 35(6), 293-300

Detailed reference viewed: 112 (2 ULg)
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See detailMicro-plasto-hydrodynamic lubrication: a fundamental mechanism in cold rolling
Laugier, Maxime; Boman, Romain ULg; Legrand, Nicolas et al

in Advanced Materials Research (2014), 966-967

Micro Plasto-Hydrodynamic (MPH) lubrication is a general mechanism in metal forming that consists in a re-lubrication of tool-piece solid contacts by an outflow of lubricant from pressurized “pockets” ... [more ▼]

Micro Plasto-Hydrodynamic (MPH) lubrication is a general mechanism in metal forming that consists in a re-lubrication of tool-piece solid contacts by an outflow of lubricant from pressurized “pockets” promoted by the plastic deformation. MPH lubrication is one of the main sources of friction variation (e.g. uncontrolled friction) in metal forming processes like strip drawing or cold rolling. This paper presents experimental results giving evidence of the MPH lubrication mechanism in cold rolling and a new lubrication model that predicts for strip drawing conditions MPH lubrication initiation and lubricant extension along the solid contacts initially in boundary condition. This MPH model could be implemented in a cold rolling model soon to help in high strength steels developments on cold rolling mills. [less ▲]

Detailed reference viewed: 87 (12 ULg)
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See detailMicro-quantitative method for analysis of sterol levels in honeybees and their pollen loads
Vanderplanck, Maryse; Michez, Denis; Vancraenenbroeck, Sophie ULg et al

in Analytical Letters (2011), 44(10), 1807-1820

A Gas Chromatography-Flame Ionization Detector method for characterization and micro-quantification of sterols was developed. The applicability of this method was evaluated for determining sterolic ... [more ▼]

A Gas Chromatography-Flame Ionization Detector method for characterization and micro-quantification of sterols was developed. The applicability of this method was evaluated for determining sterolic compounds in pollen loads, larvae, and adults of the honeybee. After a multi-step procedure to extract and purify sterols, the compounds were identified on the basis of their retention data and quantified on the basis of peak areas from analyses. Quantifications were feasible with a limited amount of samples, allowing single specimen analyses and estimation of inter-individual variation. The reliability of this microquantitative method for sterol analysis was also investigated. [less ▲]

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See detailMicro-Raman spectroscopy and chemometrical analysis for the distinction of copper phthalocyanine polymorphs in paint layers
Defeyt, Catherine ULg; Van Pevenage, Jolien; Moens, Luc et al

in Spectrochimica Acta Part A : Molecular and Biomolecular Spectroscopy (2013), 115

In art analysis, copper phthalocyanine (CuPc) is often identified as an important pigment (PB15) in 20th century artworks. Raman spectroscopy is a very valuable technique for the detection of this pigment ... [more ▼]

In art analysis, copper phthalocyanine (CuPc) is often identified as an important pigment (PB15) in 20th century artworks. Raman spectroscopy is a very valuable technique for the detection of this pigment in paint systems. However, PB15 is used in different polymorphic forms and identification of the polymorph could retrieve information on the production process of the pigment at the moment. Raman spectroscopy, being a molecular spectroscopic method of analysis, is able to discriminate between poly- morphs of crystals. However, in the case of PB15, spectral interpretation is not straightforward, and Raman data treatment requires some improvements concerning the PB15 polymorphic discrimination in paints. Here, Raman spectroscopy is combined with chemometrical analysis in order to develop a procedure allowing us to identify the PB15 crystalline structure in painted layers and in artworks. The results obtained by Linear Discriminant Analysis (LDA), using intensity ratios as variables, demonstrate the ability of this procedure to predict the crystalline structure of a PB15 pigment in unknown paint samples. [less ▲]

Detailed reference viewed: 11 (3 ULg)
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See detailMicro-scale flood risk analysis based on detailed 2D hydraulic modelling and high resolution geographic data
Ernst, Julien ULg; Dewals, Benjamin ULg; Detrembleur, Sylvain ULg et al

in Natural Hazards (2010), 55(2), 181-209

The paper presents a consistent micro-scale flood risk analysis procedure, relying on detailed 2D inundation modelling as well as on high resolution topographic and land use database. The flow model is ... [more ▼]

The paper presents a consistent micro-scale flood risk analysis procedure, relying on detailed 2D inundation modelling as well as on high resolution topographic and land use database. The flow model is based on the shallow-water equations, solved by means of a finite volume scheme on multiblock structured grids. Using highly accurate laser altimetry, the simulations are performed with a typical grid spacing of 2m, which is fine enough to represent the flow at the scale of individual buildings. Consequently, the outcomes of hydraulic modelling constitute suitable inputs for the subsequent exposure analysis, performed at a micro-scale using detailed land use maps and geographic database. Eventually, the procedure incorporates social flood impact analysis and evaluation of direct economic damage to residential buildings. Besides detailing the characteristics and performance of the hydraulic model, the paper describes the flow of data within the overall flood risk analysis procedure and demonstrates its applicability by means of a case study, for which two different flood protection measures were evaluated. [less ▲]

Detailed reference viewed: 268 (124 ULg)
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See detailMicro-simulation of Social Security reforms in Belgium
Jousten, Alain ULg; Desmet, R.; Perelman, Sergio ULg et al

in Gruber, J.; Wise, D. (Eds.) Social Security Programs and Retirement around the World: Fiscal Implications of Reform (2007)

The present paper analyzes the budgetary impact of various Social Security reforms in the Belgian institutional setting. Our approach relies on parameters that were derived in Dellis et alii (2002) using ... [more ▼]

The present paper analyzes the budgetary impact of various Social Security reforms in the Belgian institutional setting. Our approach relies on parameters that were derived in Dellis et alii (2002) using a micro-modeling strategy. Focusing our attention on a hypothetical age cohort, we illustrate the budgetary impact that the reforms considered might have on the budget of the federal government. [less ▲]

Detailed reference viewed: 56 (18 ULg)
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See detailMicro-technology for space mission
Loicq, Jerôme ULg

Conference (2007, October 03)

Detailed reference viewed: 3 (0 ULg)
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See detailMicro-usinage par laser excimère
Gailly, Patrick ULg

Learning material (2007)

Detailed reference viewed: 10 (1 ULg)