Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
See detailDesign of mechanism components using topology optimization and flexible multibody simulation
Bruls, Olivier ULg; Lemaire, Etienne ULg; Eberhard, Peter et al

in Proceedings of the 8th World Congress on Computational Mechanics (2008, July)

This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. For example, in deployable space structures, piston engines, automotive ... [more ▼]

This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. For example, in deployable space structures, piston engines, automotive suspensions, robots and high-speed machine-tools, the articulated components undergo large displacements and elastic deformations, and are subject to transient loads and nonlinear dynamic effects. The performance of such systems often depends on the mechanical design in a non-intuitive way. <br />Several researchers have addressed the optimization of the geometric parameters of mechanisms and also of the connectivity of mechanisms made of rigid members. In contrast, topology optimization techniques are often based on continuum mechanics assumptions, and usually aim at optimizing the layout of an isolated structural component under the assumption of small displacements and small deflections. In order to apply topology optimization to mechanism components, one may consider that each structural component is isolated from the rest of the mechanism and use simplified quasi-static load cases to mimic the complex loadings in service. However, two main drawbacks are associated with this approach. Firstly, defining the equivalent load cases is a rather difficult task, which is often based on trials and errors and which requires some expertise. Secondly, topology optimization is often sensitive to loading conditions, especially for multiple load cases and stress constraints, so that the optimal character of the resulting design becomes questionable if the loading is approximative. For these reasons, in order to obtain better optimal layouts, this paper proposes an optimization procedure based on dynamic simulations of the full flexible multibody system. <br />For this purpose, the nonlinear finite element approach is selected for the modelling and the simulation of the flexible multibody system. The present work is thus similar to the usual approach used in topology optimization in which the continuum domain is discretized into finite elements. The nonlinear finite element formalism accounts for both large rigid-body motions and elastic deflections of the structural components. The design variables are classically density-like parameters associated to a power law interpolation of effective material properties for intermediate densities, also known as Simply Isotropic Material with Penalization (SIMP). <br />The nonlinear equations of motion are solved using a generalized-alpha time integration scheme, and the sensitivity analysis of mechanical responses is based on a direct differentiation method. The efficient solution of the optimization problem relies on the sequential convex programming concept at the core of the CONLIN software. <br />In the present study, the method is applied to various types of mechanical systems. Firstly, planar mechanisms with truss structural components are considered. Each truss is represented by a structural universe of beams with a topology design variable attached to each one. Secondly, the discussion is extended to similar mechanisms with 3D motions. Finally, the topology optimization of spatial bodies represented by 3D finite element meshes is considered. [less ▲]

Detailed reference viewed: 113 (11 ULg)
See detailDesign of mechatronic systems with variable mechanical configuration
Da Silva, Maira; Bruls, Olivier ULg; Desmet, Wim et al

in Proceedings of the 9th International Conference on Motion and Vibration Control (MOVIC) (2008, September)

Some mechatronic systems have different spatial configurations or operation positions, and, as a consequence, their dynamic behavior, described by their most significant eigenfrequencies and mode-shapes ... [more ▼]

Some mechatronic systems have different spatial configurations or operation positions, and, as a consequence, their dynamic behavior, described by their most significant eigenfrequencies and mode-shapes, may vary in the configuration space. This inevitably affects the performance and the stability of the control system. Regarding the design of mechatronic systems with variable configuration, two main issues are treated in this paper: (i) the derivation of a parametric model able to capture the varying dynamics and the control actions, (ii) the integrated design of the structure and the controller. To cope with these issues, a parametric model is derived using a flexible multibody system technique based on the finite element method. A global modal parameterization is applied for model-order reduction, yielding a concise description of the flexible multibody model. A linear parameter varying controller is derived via interpolation of local controllers for the reduced models. This methodology is applied to a pick-and-place assembly robot with a gripper carried by a flexible beam. Eventually, design tradeoffs are evaluated considering the performance of the active system for different structural configurations. [less ▲]

Detailed reference viewed: 70 (0 ULg)
Full Text
Peer Reviewed
See detailDesign of mesoporous carbon fibers from a poly(acrylonitrile) based block copolymer by a simple templating compression moulding process
Thomassin, Jean-Michel ULg; Debuigne, Antoine ULg; Jérôme, Christine ULg et al

in Polymer (2010), 51(14), 2965-2971

Mesoporous carbon fibers were prepared by controlled pyrolysis of poly(vinyl acetate)-b-poly(acrylonitrile) (PVAc-b-PAN) copolymer located inside a cylindrical nanoporous template. A melt-compression ... [more ▼]

Mesoporous carbon fibers were prepared by controlled pyrolysis of poly(vinyl acetate)-b-poly(acrylonitrile) (PVAc-b-PAN) copolymer located inside a cylindrical nanoporous template. A melt-compression method was developed to help the penetration of the infusible copolymer inside the template without the use of any solvent that ensures the formation of completely filled fibers instead of nanotubes. The influence of the composition of the PVAc-b-PAN copolymer and the heating rate during pyrolysis on the porous morphology of the fibers was studied by transmission electron microscopy (TEM). [less ▲]

Detailed reference viewed: 110 (7 ULg)
Full Text
See detailDesign of Microswitch Systems Avoiding Stiction due to Surface Contact
Wu, Ling ULg; Noels, Ludovic ULg; Rochus, Véronique ULg et al

in SEM 2010 Annual Conference & Exposition on Experimental and Applied Mechanics (2010)

Stiction which results from contact between surfaces is a major failure mode in micro electro-mechanical systems (MEMS). Increasing restoring forces using high spring constant allows avoiding stiction but ... [more ▼]

Stiction which results from contact between surfaces is a major failure mode in micro electro-mechanical systems (MEMS). Increasing restoring forces using high spring constant allows avoiding stiction but leads to an increase of the actuation voltage so that the switch’s efficiency is threatened. A statistical rough surfaces interaction model, based on Maugis’ and Kim’s formulations is applied to estimate the adhesive forces in MEMS switches. Based on the knowledge of these forces, the proper design range of the equivalent spring constant, which is the main factor of restoring force in MEMS switches, can be determined. The upper limit of equivalent spring constant depends mainly on the expected actuator voltage and on the geometric parameters, such as initial gap size and ,thickness of dielectric layer. The lower limit is assessed on the value of adhesive forces between the two contacting rough surfaces. It mainly depends on the adhesive work of contact surfaces and on the surfaces’ roughness. In order to study more complicated structures, this framework will be used in a multiscale model: resulting unloading micro adhesive contact-distance curves of two rough surfaces will be used as contact forces in a finite-element model. In this paper the extraction of these curves for the particular case of gold to gold micro-switches is pursued. [less ▲]

Detailed reference viewed: 171 (43 ULg)
Full Text
See detailDesign of Microswitch Systems Avoiding Stiction due to Surface Contact
Wu, Ling ULg; Noels, Ludovic ULg; Rochus, Véronique et al

in Proulx, Tom (Ed.) MEMS and Nanotechnology, Volume 2 (2011)

Stiction which results from contact between surfaces is a major failure mode in micro electro-mechanical systems (MEMS). Increasing restoring forces using high spring constant allows avoiding stiction but ... [more ▼]

Stiction which results from contact between surfaces is a major failure mode in micro electro-mechanical systems (MEMS). Increasing restoring forces using high spring constant allows avoiding stiction but leads to an increase of the actuation voltage so that the switch’s efficiency is threatened. A statistical rough surfaces interaction model, based on Maugis’ and Kim’s formulations is applied to estimate the adhesive forces in MEMS switches. Based on the knowledge of these forces, the proper design range of the equivalent spring constant, which is the main factor of restoring force in MEMS switches, can be determined. The upper limit of equivalent spring constant depends mainly on the expected actuator voltage and on the geometric parameters, such as initial gap size and thickness of dielectric layer. The lower limit is assessed on the value of adhesive forces between the two contacting rough surfaces. It mainly depends on the adhesive work of contact surfaces and on the surfaces’ roughness. In order to study more complicated structures, this framework will be used in a multiscale model: resulting unloading micro adhesive contact-distance curves of two rough surfaces will be used as contact forces in a finite-element model. In this paper the extraction of these curves for the particular case of gold to gold micro-switches is pursued. [less ▲]

Detailed reference viewed: 92 (24 ULg)
Full Text
Peer Reviewed
See detailDesign of Movable Weirs and Storm Surge Barriers
Rigo, Philippe ULg; Abdelnour, R.; Bulckaen, D. et al

in PIANC 2006, 31ème Congrès de l’PIANC (Article 031) (2006, May)

Detailed reference viewed: 91 (3 ULg)
Full Text
See detailDesign of movables Weirs and Storm Surge Barriers
Rigo, Philippe ULg; Abdelnour, R.; Bulckaen, D. et al

Book published by PIANC - INCOM (2006)

State of of in the dsign of movable weirs and storm surge barriers

Detailed reference viewed: 399 (26 ULg)
Full Text
See detailDesign of Muong Chuoi, Kinh-Lo and Thu-Bo Barriers (report Jan 2011)
Rigo, Philippe ULg

Report (2011)

Consulting activities for the water level control for flood protection of HCMC area Design of Muong Chuoi, Kinh-Lo and Thu-Bo Barriers ICMB-9, HCMC, Vietnam

Detailed reference viewed: 73 (1 ULg)
See detailDesign of nanoobjects endowed with specific properties
Willet, Nicolas ULg; Qiu, Hongjin; Rieger, Jutta ULg et al

Conference (2004, March)

Detailed reference viewed: 7 (3 ULg)
See detailDesign of new multifunctional nanocarriers for protein delivery
Parilti, Rahmet ULg; Jérôme, Christine ULg; Howdle, Steven M. et al

Conference (2015, May 18)

Polymeric nanoparticles have been extensively investigated for their biomedical applications especially as drug carriers. However, efficient encapsulation and delivery of therapeutic proteins in targeted ... [more ▼]

Polymeric nanoparticles have been extensively investigated for their biomedical applications especially as drug carriers. However, efficient encapsulation and delivery of therapeutic proteins in targeted manner still present challenges. This project aims to develop a novel one-pot strategy to obtain nanoparticles able to carry proteins in their core, as well as bearing targeting and/or imaging agents on their surface. In addition to this objective, polymerizations are carried out in supercritical carbon dioxide (scCO2), which confers environmentally benign features to the process. Dispersion polymerizations of hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA) in are carried out in scCO2 in the presence of an initiator, cross-linker and CO2-philic photoclevable stabilizer. Upon exposure to UV light, the o-nitrobenzyl junctions present at the surface of the particles are cleaved, thus providing water dispersible hydrogels. Spherical monodisperse nanoparticles were successfully synthesized in scCO2 with two different conditions. Milder reaction conditions were achieved by using 2,2'-Azobis(4-methoxy-2,4-dimethyl valeronitrile (V70) as an initiator which opens up the platform for one-pot protein encapsulation in scCO2. [less ▲]

Detailed reference viewed: 86 (5 ULg)
Peer Reviewed
See detailDesign of new potential hypoglycemic drugs
Masereel, B.; De Tullio, Pascal ULg; Dogne, J.-M. et al

in Journal de Pharmacie de Belgique (1998), 53

Detailed reference viewed: 4 (0 ULg)
Peer Reviewed
See detailDesign of new potential hypoglycemic drugs
Masereel, B.; De Tullio, Pascal ULg; Dogne, J. M. et al

Poster (1997, May)

Detailed reference viewed: 8 (0 ULg)
See detailDesign of new stealthy and pH-sensitive polymer micelles for potential solid tumor targeting
Van Butsele, Kathy

Doctoral thesis (2008)

Detailed reference viewed: 64 (30 ULg)
See detailDesign of novel copolymers by cobalt-mediated radical polymerization of N-vinyl amides
Debuigne, Antoine ULg

Conference (2012, September 21)

Detailed reference viewed: 18 (5 ULg)
See detailDesign of novel polyphosphoesters (co)polymers for improving a drug delivery system based on calcium carbonate particles
Ergül, Zeynep ULg; Boury, Frank; Debuigne, Antoine ULg et al

Poster (2013, October)

Biomedical applications, especially drug delivery systems, often require biodegradable and biocompatible materials that permit safe retention as well as controlled delivery of a drug. CaCO3 particles are ... [more ▼]

Biomedical applications, especially drug delivery systems, often require biodegradable and biocompatible materials that permit safe retention as well as controlled delivery of a drug. CaCO3 particles are safe and biodegradable drug carriers that have excellent properties such as low density, high specific surface areas and porosity for drugs microencapsulation. The encapsulation of a model protein within CaCO3 particles has been successfully investigated by Boury and coworkers but the release profiles still need to be improved. In this project, we would like to slow down the kinetics of protein release. One strategy consists in loading the CaCO3 particles with degradable micelles containing the protein/drug in their core. In this perspective, we have developed a novel class of degradable polyphosphoesters (PPE) (co)polymers able to self-assemble into micelles. Note that the degradation products of PPEs, like phosphates, associated with calcium from the inorganic carrier could favor some reconstruction processes like bone regeneration. Pendant carboxylic acid functions were introduced along the backbone of the copolymers in order to increase their affinity for calcium and facilitate their incorporation in the CaCO3 particles. First, an alkynyl-functionalized phospholane monomer, i.e. butynyl phosphate (BYP), was prepared by condensation of 2-chloro-2-oxo-1,3,2-dioxaphospholane and 3-butyn-1-ol (43 % yield), according to a reported procedure. Then, a series of well-defined (Ɖ < 1.2) alkyne-containing PBYP (co)polymers were synthesized by ring opening polymerization using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and thiourea (TU) as catalysts[5] (see scheme below). The structures of the PPE (co)polymers were characterized by 1H NMR, 31P NMR and size exclusion chromatography (SEC). Next, carboxylic acid functions were introduced along the PPE backbone by click-type thiol-yne addition of mercaptopropionic acid onto the pendant alkynes. The degradability of the PPEs was investigated at different pH. In the future, the self-assembly behavior of the PPE-based copolymers will be studied as well as their drug loading capacity and ability to accumulate within the CaCO3 particles. In addition, the acid-bearing PPE-based copolymers will be tested as templating agents for the synthesis of CaCO3 particles. [less ▲]

Detailed reference viewed: 72 (6 ULg)