518 research outputs found
Interval field implementations for spatial uncertainty processing in non-deterministic FE analysis
No full textThis paper discusses the application of interval fields for the analysis of uncertain mechanical structures. More specifically, this work illustrates the use of interval fields to represent uncertainties with spatially distributed uncertain parameters in the context of finite element analysis. Four different mathematical interval field implementations are in- troduced and their effcieny and accuracy is compared. Finally, these implementations are illustrated and validated using a static stress analysis of a conical shell structure. © 2013 by Wim Verhaeghe, Wim Desmet, Dirk Vandepitte and David Moens.status: Publishe
Pragmatic features in the language of cross-cultural virtual teams: A roundtable discussion of student-to-student discourse in international collaborative project
No full textThis presentation contains some of the findings by the cross-cultural virtual team (CCVT) of the Trans-Atlantic network - made up by John Humbley (University of Paris-Denis Diderot), Matthew Livesey (University of Wisconsin-Stout), Bruce Maylath (North Dakota State University), Birthe Mousten (Aarhus University), Federica Scarpa (University of Trieste), Sonia Vandepitte (University College Ghent) and Lucy Veisblat (University of Paris-Denis Diderot) - during collaborative projects consisting of students' virtual exchanges which they have carried out for many years by drawing on each team member’s expertise in translation and technical communication. In particular, it examines the pragmatic features of the communication between CCVT members which have given rise to the emergence of a language for the specific purpose of collaboration. In addition, it provides methods for analyzing and teaching this language use among CCVT members
Experimental dataset: stereo-DIC experiment on uniaxially loaded, S-Shaped, high density polyethylene test sample
No full textStereo-DIC experiments were performed on uniaxially loaded, s-shaped, high-density polyethylene test sample. 100 stationary images of unloaded test sample were taken for evaluation of DIC noise floor. Stereo calibration image dataset, involving a calibration target with rectangular grid (12 by 9 and pitch of 10 mm), is also made available. Tensile load from the test bench load-cell sampled at each moment an image is captured is available.</span
Interactivities Between Professional Translators and Professional Communicators: What Translators Would Like Communicators to Know
No full textThis tutorial is designed to acquaint professional communicators with the challenges that professional translators face when localizing the texts that communicators send them for translation. The presenters will engage participants in activities that will demonstrate terminology management, notional equivalence, culturally bound references, and revising and reviewing
Calculation of the complete shortening-load curve for an imperfect strut (met Dirk V.H. Vandepitte). Festschrift Udo Vogel. Universität Karlsruhe, März 1993, pp. 173-184.
No full textOntwikkeling van een golfgebaseerde voorspellingstechniek voor de efficiënte laag- en middenfrequente structuurdynamische analyse
No full textDit proefschrift beschrijft de ontwikkeling van een golfgebaseerde voorspellingstechniek voor de analyse van het trillingsgedrag van mechanische constructies. De huidige technieken voor de trillingsanalyse van een constructie zijn voornamelijk gebaseerd op deterministische technieken, zoals de eindige elementenmethode. De toenemende rekenkundige belasting voor toenemende frequenties beperkt de praktische toepasbaarheid van de eindige elementenmethode tot het laagfrequente gebied. De golfgebaseerde methode is een alternatieve deterministische methode gebaseerd op de indirecte Trefftz methode. De kleinere rekenkundige belasting van de golfgebaseeerde methode verhoogt de toepasbaarheid van de techniek naar het middenfrequente gebied. Dit proefschrift rapporteert over de ontwikkeling van de golfgebaseerde methode voor de trillingsanalyse van constructies bestaande uit vlakke platen. Een gedetailleerde performantiestudie toont aan dat de golfgebaseerde methode rekenefficiënter is dan de eindige elementenmethode, wat nauwkeurige voorspellingen bij hogere frequenties toelaat. De efficiëntie van de golfgebaseerde methode is echter het meest uitgesproken voor problemen met een beperkte geometrische complexiteit. Om de algemene toepasbaarheid van de methode te verhogen is een hybride koppeling met de eindige elementenmethode voorgesteld. Deze combineert de rekenkundige efficiëntie van de golfgebaseerde methode met de geometrische flexibiliteit van de eindige elementenmethode. Numerieke validatievoorbeelden tonen de haalbaarheid en verhoogd prestatievermogen van de hybride methode aan.status: Publishe
Wave Based Modelling Techniques for Unbounded Acoustic Problems
No full textIn recent years, the industrial design process has become increasingly dependent on numerical CAE tools to replace the time-consuming and expensive prototype testing. A competitive market driven by a consumer focus urges designers to take into account many product properties. Amongst those, the acoustic characteristics are quickly gaining importance; a trend which is amplified by recent legislations regarding noise and acousticcomfort.A survey of the state-of-the-art techniques reveals that the construction of an accurate and reliable numerical model of an acoustic problem is not a trivial task. Dedicated techniques have been developed to successfully solve the acoustic problem both at low and high frequencies. However, both approaches fall short in covering an important mid-frequency range, in which the typical wavelengths are neither very largenor very small compared to the problem dimensions. The unbounded natureof many acoustic problems --- think of an object radiating sound into the environment --- further complicates matters: many simulation techniques based on a problem discretisation can only be used after a reformulation of the problem to an equivalent bounded form.The work presented here is framed in the development of the Wave Based Method (WBM), a novel simulation technique for steady-state dynamic problems. Using a wave-like Trefftz basis, the WBM is able to deliver accurate predictions in the difficult mid-frequency range. Until now, the development of the WBM focussed on bounded acoustic problems. A first contribution of this work consists in the further development of the method to efficiently deal with unbounded problems, including radiation, scattering and diffraction.The second contribution focusses on the geometrical limitations of the WBM. The flexibility of the method is an important point of attention:the use of a Trefftz basis is very efficient, but imposes some constraints on the problem geometry. A multi-level framework for WBM calculations is proposed, which allows an elegant and efficient solution of complexmultiple-scatterer problems. Moreover, an extension of the existing hybrid FE-WBM to unbounded problems enables the treatment of scatterers with a geometrically detailed surface.Both contributions are validated through a series of numerical examples, illustrating the applicability and efficiency of the developed techniques, in relation to the current state-of-the-art.status: Publishe
Wave Based Modelling Methods for Steady-State Vibro-Acoustics
No full textThis dissertation considers the development of wave based prediction methods for the analysis of steady-state vibro-acoustic problems. Conventional element based prediction methods, such as the finite element method(FEM), are commonly used, but are restricted to low-frequency applications. The wave based method (WBM) is an alternative deterministic technique which is based on the indirect Trefftz approach. The WBM is computationally very efficient, allowing the analysis of problems at higher frequencies. This dissertation reports on an extension of the WBM to multi-domain acoustic problems and problems involving unbounded acoustic fluid domains, such as transmission, scattering and radiation problems. The efficiency of the WBM is most pronounced for problems of moderate geometrical complexity. A hybrid finite element-wave based method combines the strengths of the two methods, namely, the high computational efficiency ofthe WBM and the ability of the FEM to model problems of arbitrary geometrical complexity. Numerical validation examples show the enhanced computational efficiency of the WBM for problems of moderate geometrical complexity and of the hybrid method for real-life engineering problems.status: Publishe
Study on the influence of design parameter variation on the dynamic behaviour of thermoplastic honeycomb panels
No full textSandwich panels are layered structures that consist of at least five layers : two thin face sheets that are bonded with bonding layers to the thick core. The core has a very low density whereas the face sheets are stiff and strong. The entire panel combines high mechanical properties with a very low areal mass. Most of the structural characteristics of the panel (material selection and thickness of each layer) can be selected independently of other parameters, and the overall characteristics of the panel depend on the particular selection of parameters. Because of the wide range of panel parameters, numerical modelling is useful to provide insight into the structural characteristics of a particular panel.
This paper studies the effect of design parameter variations on the dynamic behaviour of honeycomb sandwich panels. The dynamic behaviour includes natural frequencies, mode shapes and damping of such panels with free boundary conditions.
In the first section the structure of honeycomb sandwich panels is illustrated, in particular those with a ThermHex core. For a typical honeycomb panel the different design parameters are outlined.
Natural frequencies and mode shapes can be predicted approximately using analytical models. Some of the methods are outlined in this article.
The second section of the paper presents the numerical modelling of a sandwich panel using commercial finite element codes. Different core modelling strategies are compared, e.g. geometrically correct or as a homogenised equivalent material. Advantages and drawbacks of the different methods are outlined. Different ways of modelling damping in the panels are also presented.
The third section discusses the experimental validation. To validate the finite element models, measurements are carried out on some test panels. Free-free boundary conditions are provided by elastically suspending the panels. To make measurements totally contactless, the test panels are excited acoustically and the vibration measurement is performed with a laser vibrometer. The way the data are captured and processed is also outlined.
Measured natural frequencies and mode shapes are compared with the calculated results from the different FE models and the analytical models. The techniques that are used for this comparison are briefly discussed.
The different FE models are updated using results from a sensitivity analysis. This analysis is performed theoretically for every design parameter and is discussed in detail. Results from the updated models are again compared with those obtained from measurements.
The uncertainty on different design parameters is studied and discussed. The influence of these various uncertainties on the natural frequencies and mode shapes is investigated using Monte Carlo simulations.status: Publishe
On the use of an efficient wave based method for steady-state structural dynamic analysis
No full textThe Finite Element Method is the most commonly used prediction technique for dynamic simulations of mechanical structures. Given the increasing model sizes and subsequent increasing computational load for increasing frequency, the use of the Finite Element Method (FEM) is limited to low-frequency applications. The Wave Based Method (WBM) is a novel Trefftz-based deterministic prediction technique that is capable of relaxing the existing frequency limit. This paper gives an overview of the principles of the WBM for the steady-state dynamic analysis of structures. First the flat plate bending and membrane behaviour are described. Subsequently, the theory for these two problems is united to handle non-coplanar flat plate assemblies. Finally, a hybrid FE-WBM is shown, which combines the strengths of the FEM and the WBM. Throughout the paper the performance of the WBM is compared with that of the FEM, which demonstrates the enhanced computational efficiency of the WBM.status: Publishe
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