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
Peer Reviewed
See detailEquilibrium models in multimodal container transport systems
Corman, Francesco; Viti, Francesco UL; Negenborn, Rudy

in Flexible Services and Manufacturing Journal (2017), 29

Detailed reference viewed: 189 (6 UL)
Full Text
See detailErmüdungseigenschaften des Wabenkerns von sandwichpaneelen aus Aluminium
Wahl, Laurent UL

Doctoral thesis (2013)

In comparison to their weight, honeycomb composite structures have a high bending stiffness, which makes them very suited for every application where little weight is important, like airplanes, railway ... [more ▼]

In comparison to their weight, honeycomb composite structures have a high bending stiffness, which makes them very suited for every application where little weight is important, like airplanes, railway-cars and vehicles. These structures are subjected to cyclic loading. The sandwich panels consist of two thin and stiff aluminium face sheets, which are bonded to a thick and lightweight aluminium honeycomb core. The shear stresses in the core of these structures depend strongly on the angle of the load application, because the core is not homogeneous. The distribution and the level of the shear stresses are investigated using analytical calculations. The load direction which induces highest stresses in the honeycomb core is derived. This direction is not the W-direction, which is the most compliant one. In literature, there are few fatigue properties of the honeycomb core described. The fatigue properties of the core are investigated in this work using the finite element method and experiments. The experimental investigations consist of three-point bending tests, pulsating roller tests, Food-Cart Roller tests and several tests on real components. Depending on the load application, the honeycomb core fails either through core indentation or shear failure. Several fatigue tests were carried out at constant load amplitude and the failure mode is investigated. The sandwich structures were modeled with the ANSYS finite element software. The number of elements is reduced by replacing the honeycomb core with a homogeneous core with orthotropic properties. In order to get the stresses in the honeycomb core at the critical location, a submodel was created. In this work, some equations are derived in order to calculate the real shear stresses from the shear stresses of the homogeneous core. In addition, imperfections are included in the model. Furthermore, buckling analyses were used to examine core indentation failure. Based on these simulations, both failure modes described above can be explained. Core indentation occurs, when the honeycomb cells are buckling due to the load application. The buckling of the cells can be avoided by using a smoother load application. In this case, the core fails in the three-point bending test by shear failure. The fatigue life of the examined specimens is successfully approximated in this manuscript, with the lifetime analysis being based on the FKM-guideline. Every simulation is validated by experimental results. [less ▲]

Detailed reference viewed: 138 (11 UL)
Full Text
Peer Reviewed
See detailError estimation and bounding in energy norm based on a displacement recovery technique
Nadal, E.; González-Estrada, O. A.; Ródenas, J. J. et al

in Eberhardsteiner, Josef; Böhm, Helmut; Rammerstorfer, F G (Eds.) 6th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012) (2012)

Detailed reference viewed: 87 (4 UL)
Full Text
Peer Reviewed
See detailError estimation and error bounding in energy norm based on a displacement recovery technique
Nadal, E.; González-Estrada, O. A.; Ródenas, J. J. et al

in ECCOMAS 2012 - European Congress on Computational Methods in Applied Sciences and Engineering, e-Book Full Papers (2012)

Traditionally, recovery based error estimators in linear elasticity have considered the evaluation of an enhanced stress field obtained from the raw Finite Element (FE) stress solution. Instead of that ... [more ▼]

Traditionally, recovery based error estimators in linear elasticity have considered the evaluation of an enhanced stress field obtained from the raw Finite Element (FE) stress solution. Instead of that, one can also obtain a recovered displacement field from the FE displacements. Herein, we describe a superconvergent patch recovery of the displacement field which considers the local fulfilment of boundary and internal equilibrium equations, Dirichlet constraints and, for singular problems, the splitting of the displacement and stress fields into singular and smooth parts. Numerical tests using problems with known analytical solution have been carried out to validate the proposed technique for error estimation and error bounding in energy norm and quantities of interest. [less ▲]

Detailed reference viewed: 228 (2 UL)
Full Text
Peer Reviewed
See detailError estimation and error bounding in quantities of interest based on equilibrated recovered displacement fields
Nadal, E.; González-Estrada, O. A.; Ródenas, J. J. et al

in ECCOMAS 2012 - European Congress on Computational Methods in Applied Sciences and Engineering, e-Book Full Papers (2012)

Over the last ten years there has been an increase on the use of goal-oriented error estimates aimed to quantify the local error on a (non)linear quantity of interest (QoI) that might result relevant for ... [more ▼]

Over the last ten years there has been an increase on the use of goal-oriented error estimates aimed to quantify the local error on a (non)linear quantity of interest (QoI) that might result relevant for design purposes. Residual-based error estimators have been used recursively to obtain upper and lower bounds of the error in quantities of interest for finite element approximations. In this paper, we present a recovery technique for 2D linear elasticity problems, based on the superconvergent patch recovery (SPR), which provides recovered displacement and stress fields that are then utilised to evaluate practical upper and lower error bounds in QoI. [less ▲]

Detailed reference viewed: 238 (2 UL)
Full Text
Peer Reviewed
See detailError estimation and space-time adaptivity for the isogeometric analysis of transient structural dynamics
Yu, Peng; Claus, Susanne; Bordas, Stéphane UL et al

Scientific Conference (2016, April 01)

This paper presents a new adaptive scheme for the error-controlled simulation of transient dynamics problem. We rely on spline bases for the higher-order spatial description of our kinematic fields. Local ... [more ▼]

This paper presents a new adaptive scheme for the error-controlled simulation of transient dynamics problem. We rely on spline bases for the higher-order spatial description of our kinematic fields. Local adaptivity is performed by employing a hierarchical T-mesh technology, in combination with geometry independent field approximation. The Newmark algorithm is chosen to solve the semidiscrete equation of motion. We will present some simple local error estimates to drive the adaptivity, and show how we can ensure that the mechanical energy of conservative systems is preserved during the refinement process. [less ▲]

Detailed reference viewed: 101 (4 UL)
Full Text
See detailError estimation in homogenisation
Alves Paladim, Daniel; Kerfriden, Pierre; Moitinho de Almeida, José et al

Presentation (2015, January 30)

Detailed reference viewed: 103 (3 UL)
Full Text
Peer Reviewed
See detailError estimation in quantities of interest for XFEM using recovery techniques
González-Estrada, O. A.; Nadal, E.; Ródenas, J. J. et al

in Yang, Z J (Ed.) 20th UK National Conference of the Association for Computational Mechanics in Engineering (ACME) (2012)

Detailed reference viewed: 227 (2 UL)
Full Text
Peer Reviewed
See detailError estimation of recovered solutions in FE analysis. Higher order h-adaptive refinement strategies
Ródenas, J. J.; Nadal, E.; González-Estrada, O. A. et al

in Pimienta, P M (Ed.) 10th World Congress on Computational Mechanics (WCCM 2012) (2012)

Detailed reference viewed: 211 (2 UL)
Full Text
Peer Reviewed
See detailError-controlled adaptive extended finite element method for 3D linear elastic crack propagation
Jin, Y.; González-Estrada, O. A.; Pierard, O. et al

in Computer Methods in Applied Mechanics & Engineering (2017), 318

We present a simple error estimation and mesh adaptation approach for 3D linear elastic crack propagation simulations using the eXtended Finite Element Method (X-FEM). A global extended recovery technique ... [more ▼]

We present a simple error estimation and mesh adaptation approach for 3D linear elastic crack propagation simulations using the eXtended Finite Element Method (X-FEM). A global extended recovery technique (Duflot and Bordas, 2008) is used to quantify the interpolation error. Based on this error distribution, four strategies relying on two different mesh optimality criteria are compared. The first aims at homogenizing the error distribution. The second minimizes the total number of elements given a target global error level. We study the behaviour of these criteria in the context of cracks treated by an X-FE approach. In particular, we investigate the convergence rates at the element-level depending its enrichment type. We conclude on the most suitable refinement criterion and propose and verify a strategy for mesh adaptation on 3D damage tolerance assessment problems. [less ▲]

Detailed reference viewed: 86 (3 UL)
Full Text
Peer Reviewed
See detailError-controlled computational fracture mechanics
Bordas, Stéphane UL

Scientific Conference (2017, July 12)

Detailed reference viewed: 348 (32 UL)
Full Text
Peer Reviewed
See detailEstimación precisa del error en magnitudes de interés mediante técnicas de recovery con equilibrio local
Nadal, E.; Ródenas, J. J.; González-Estrada, O. A. et al

in Congress on Numerical Methods in Engineering (2011)

Detailed reference viewed: 74 (1 UL)
Full Text
Peer Reviewed
See detailEstimating bike-share trips using station level data
Medard de Chardon, Cyrille UL; Caruso, Geoffrey UL

in Tranportation Research Part B: Methodological (2015), 78

Bicycle sharing systems (BSS) have increased in number rapidly since 2007. The potential benefits of BSS, mainly sustainability, health and equity, have encouraged their adoption through support and ... [more ▼]

Bicycle sharing systems (BSS) have increased in number rapidly since 2007. The potential benefits of BSS, mainly sustainability, health and equity, have encouraged their adoption through support and promotion by mayors in Europe and North America alike. In most cases municipal governments desire their BSS to be successful and, with few exceptions, state them as being so. New technological improvements have dramatically simplified the use and enforcement of bicycle return, resulting in the widespread adoption of BSS. Unfortunately little evaluation of the effectiveness of differently distributed and managed BSS has taken place. Comparing BSS systems quantitatively is challenging due to the limited data made available. The metrics of success presented by municipalities are often too general or incomparable to others making relative evaluations of BSS success arduous. This paper presents multiple methodologies allowing the estimation of the number of daily trips, the most significant measure of BSS usage, based on data that is commonly available, the number of bicycles available at a station over time. Results provide model coefficients as well as trip count estimates for select cities. Of four spatial and temporal aggregate models the day level aggregation is found to be most effective for estimation. In addition to trip estimation this work provides a rigorous formalization of station level data and the ability to distinguish spatio-temporal rebalancing quantities as well as new characteristics of BSS station use. [less ▲]

Detailed reference viewed: 127 (8 UL)
Full Text
Peer Reviewed
See detailEstimating fibres' material parameter distributions from limited data with the help of Bayesian inference
Rappel, Hussein UL; Beex, Lars UL

in European Journal of Mechanics. A, Solids (2019), 75

Numerous materials are essentially structures of discrete fibres, yarns or struts. Considering these materials at their discrete scale, one may distinguish two types of intrinsic randomness that affect ... [more ▼]

Numerous materials are essentially structures of discrete fibres, yarns or struts. Considering these materials at their discrete scale, one may distinguish two types of intrinsic randomness that affect the structural behaviours of these discrete structures: geometrical randomness and material randomness. Identifying the material randomness is an experimentally demanding task, because many small fibres, yarns or struts need to be tested, which are not easy to handle. To avoid the testing of hundreds of constituents, this contribution proposes an identification approach that only requires a few dozen of constituents to be tested (we use twenty to be exact). The identification approach is applied to articially generated measurements, so that the identified values can be compared to the true values. Another question this contribution aims to answer is how precise the material randomness needs to be identified, if the geometrical randomness will also influence the macroscale behaviour of these discrete networks. We therefore also study the effect of the identified material randomness to that of the actual material randomness for three types of structures; each with an increasing level of geometrical randomness. [less ▲]

Detailed reference viewed: 164 (32 UL)
Full Text
Peer Reviewed
See detailEstimation and its Role in Engineering Design - An Introduction
Adolphy, Sebastian; Gericke, Kilian UL; Blessing, Lucienne UL

in Proceedings of the 17th International Conference on Engineering Design (2009)

Estimation is assumed to be a relevant method for problem solving in product development due to the deficiencies in information availability and certainty, as well because of short resources. Nevertheless ... [more ▼]

Estimation is assumed to be a relevant method for problem solving in product development due to the deficiencies in information availability and certainty, as well because of short resources. Nevertheless estimation as a method is hardly mentioned in literature on product development nor is it part of engineering education. As a consequence good performance in estimation and the development of estimation competence is left to chance, i.e. expected to be built up through experience. We believe that estimation can be supported and taught. Hence estimation competence can be developed purposive and more quickly. The aims of the research introduced in this paper are to understand relevance and functioning of estimation in engineering design, and to develop support for engineering practice and education based on this understanding. This paper focuses on demonstrating the topics’ relevance by addressing the following questions: •Why is estimation important for engineering design? •What is the state of the art in understanding estimation in general? •What is the state of the art of estimation as a method in engineering design? On the basis of this initial investigation we propose our research framework. After goal, approach and scope of our research, the main research questions on estimation in engineering design we wish to answer are formulated, and the research methods we are using. Furthermore first results on characteristics of estimation in engineering design identified by tests, as well as video and protocol analysis are summarized. At least an outlook on the prospect research is given. [less ▲]

Detailed reference viewed: 75 (0 UL)
See detailEtude biomécanique comparative de cinq différents systèmes de fixation utilisés dans les cas d'ostéotomies tibiales valgisantes: Essais expérimentaux et simulations numériques incluant les forces musculaires
Diffo Kaze, Arnaud UL

Doctoral thesis (2016)

This research project was carried out in partnership with the Orthopaedic and Traumatology service of the “clinique d’Eich” of the Centre Hospitalier de Luxembourg. The main objective consisted in a ... [more ▼]

This research project was carried out in partnership with the Orthopaedic and Traumatology service of the “clinique d’Eich” of the Centre Hospitalier de Luxembourg. The main objective consisted in a comparative biomechanical study of the stability of five different currently used implants for open-wedge high tibial osteotomy (HTO). The following implants were tested in the comparative biomechanical study: Contour Lock HTO, PEEKPower HTO, iBalance HTO, TomoFix standard and TomoFix small stature. The implants were chosen freely from the market and there has not been any funding or link to any of the manufacturers. The comparison was first made experimentally using static compression loading to failure and dynamic loading to failure tests, then computationally using simulations by mean of the finite element method. Muscle forces were predicted using musculoskeletal modeling and applied to the finite element models of the lower limb that simulated the stance phase of the gait cycle. The finite element models created included all the bones of the lower limb, except those of the foot, as well as the menisci, the articular cartilage layers of the knee and the patellar tendon which was modelled by springs. The comparative study using numerical simulations was done considering two separate loadings: (1) application of a compressive load on the tibial plateau and (2) consideration of muscle forces. The comparison of the two types of loading (1) and (2) showed that loading (1) used during the mechanical tests is compatible with a realistic loading of the tibia with the leg at 15 % of the gait cycle during slow walking. Observations from numerical simulations considering loading (2) emphasized the necessity to take into account the muscle forces in the testing protocols and implant design process. The results of the numerical simulations considering loading (1) were in line with the findings of the experimental study. All the implants tested showed sufficient stability during static loading. All the specimens failed due to fracture of the opposite cortical bone. In regards to the results of this study, the implant iBalance offered the best mechanical stability to the operated tibia, and the PEEKPower plate the worst. Simplifications were made to reduce the complexity of the different physical and numerical models; hence the transposition of the obtained results to clinical settings should be done with precaution. There is no conflict of interest in relation to this work. [less ▲]

Detailed reference viewed: 180 (27 UL)
See detailThe European Association for Data Science, its main goals and tasks
Krolak-Schwerdt, Sabine; Böhmer, Matthias UL

Presentation (2016, December)

Detailed reference viewed: 25 (2 UL)
See detailEuropean Conference on Data Analysis 2013. Book of Abstracts.
Lausen, Berthold; Krolak-Schwerdt, Sabine UL; Böhmer, Matthias UL

Book published by University of Luxembourg (2013)

Detailed reference viewed: 180 (7 UL)
Full Text
Peer Reviewed
See detailEvaluating the effects of information reliability on travellers’ route choice
Bifulco, Gennaro N.; Di Pace, Roberta; Viti, Francesco UL

in European Transport Research Review (2013)

Purpose This paper analyses travellers’ behaviour with respect to route choice in a context where an Advanced Traveller Information System (ATIS) is in place. ATIS are important applications in the field ... [more ▼]

Purpose This paper analyses travellers’ behaviour with respect to route choice in a context where an Advanced Traveller Information System (ATIS) is in place. ATIS are important applications in the field of intelligent transportation systems (ITS). However, the practical impact of ATIS is still a matter for debate, and identification of expected route choice behaviour under ATIS is one of themain ways to assess their practical importance. Methods Travellers’ choices are frequently explored by means of stated preference (SP) approaches. In this paper we discuss some issues to be addressed when an SP survey is carried out, with particular reference to cases where a repeated choice approach is employed in the survey. Results Our analysis concerns an application of the SP approach in a pilot study aimed at identifying the effects of ATIS accuracy on travellers’ compliance with information. Conclusions This paper aims tomake two major contributions. First of all, empirical analyses based on proper indicators and statistical tests are suggested in order to evaluate how the collected data have to be handled in order to eliminate transient route-choice observations. These are due to the warm-up phase inherently associated with the survey method adopted, dealing with repeated choices. Secondly, we analyse (stationary) route choice in order to assess the effects of information reliability (and the kind of information) on both route choice and compliance. [less ▲]

Detailed reference viewed: 114 (6 UL)