Annual Report Department

3Projects

3.1Structural design and analysis

3.1.1Growth project GRD1-2000-25828, ECOSYSTEMS: Advanced Machining Systems for Environmentally Friendly Manufacturing

Partners: CRF (I), Guehring (D), RWTH/WZL (D), COMAU (I), K.U.leuven-PMA (B), Kessler (D), Rexroth-star

(D), PLATIT (CH), Nathan (ESP)

Objective: The main objectives of the project is to develop new machine concepts, components, systems equipment and tools aimed at improving environmental impact of flexible machining transfer lines for medium/large-batch production of mechanical components of difficult to cut materials (magnesium, CGI cast iron, overeutectic aluminium).

The project will address the following fundamental areas: (1) the design and development of environmentally conscious high speed machining and workpiece transport systems, (2) the development of advanced integrated CAD/CAE, testing and monitoring platform to support environmentally friendly machine tool design, and (3) the optimisation of high speed dry machining processes for components in difficult-to-cut materials.

Period: Oct 2001 – Jan 2004

Contact: H. Van Brussel, F. Al-Bender, P. Sas

3.1.2IWT project 000270/Picanol: Development of methods and techniques to reduce the radiated noise and the vibrations of machines with mechanisms imposing oscillating motions.

Partners: Picanol N.V., WTCM, KULeuven-PMA

Objective: Mechanisms that impose oscillating movements generate dynamical forces, giving rise to machine vibrations due to the finite stiffness of the mechanisms and the supporting structures. These vibrations propagate through the machine structure, towards other systems connected with the original mechanisms. A side-effect of these vibrations is the noise radiated by the machine. The purpose of this research is to develop methods to reduce these vibrations and radiated noise.

Period: Apr 2000 – Jun 2003

Contact: J. De Schutter

3.1.3TAP project no. PA-01-314 "Static and dynamic design analysis procedures for structures with uncertain parameters"

Partners: WTCM (Heverlee, B), Belgian Building Research Institute (Limelette, B), Université de Liège (B), K.U.Leuven - BWM, K.U.Leuven - PMA

Objective: the objective of this project is the development of a consistent and feasible methodology to take into account the effect of parameter uncertainties, using only real physical and geometrical properties of the structure. The consistent character means that the method has to be developed in an analytical framework that is as close as possible to existing finite element methods. The feasible aspect of the methodology implies that the user should be able to apply the method without much extra knowledge other than standard finite element procedures, and also that the calculation time should not be excessive. The project covers both static and dynamic analysis procedures. The methods will be applied to build up a fundamental understanding of realistic design criteria for both static and dynamic analysis, and finally to compare these rules to existing design procedures.

Period: Jan 2003 – Dec 2005

Contact: D. Vandepitte, W. Desmet

3.2Noise and vibration engineering

3.2.1FWO-project G.0123.01, EDSVS: European Doctorate in Sound and Vibration Studies – Marie Curie Fellowship

Partners: ISVR Southampton (UK), ONERA (FR), INSA Lyon (FR), KUL (B), Trinity College Dublin (IRL), Univ. di Ferrara (IT), DMMMSA Padova (IT), Technical University Denmark (DK)

Objective: The aim of the network is to provide doctoral training programmes for European students in highly qualified European Universities and Higher Education Centres working in the field of vibration and acoustics. The objectives are

• 
  to promote a “European Doctorate in Vibration and Acoustics” for European students to be carried out (normally) in two different European University Centres
  
• 
  to bring together the unique teaching and research features of highly qualified European University Centres with complementary expertise working on vibration and acoustics related topics.
  
• 
  to create a link between academic and industrial bodies in Europe.
  
• 
  to assist the development of less favoured regions in Europe by offering training to young students from less favoured regions and by allowing industries of less favoured regions to co-operate with the Universities through the doctorate programmes
  

Period: Jan 2000 – Dec 2004

Contact: P. Sas, W. Desmet

3.2.2FWO project G.0381.00 Design and validation of advanced system identification techniques in the field of operational modal analysis

Partners: VUB-Werktuigkunde, KULeuven-PMA

Objective: The aim of this project is to improve the reliability of operational modal testing. The idea consists in using multi-variable frequency-domain Maximum Likelihood identification techniques adapted in order to derive the modal parameters of interest from output-only operational response measurements.

Period: Jan 2000 – Dec 2003

Contact: J. Swevers, W. Heylen

3.2.3FWO Project no.G0123.01: 'Design and development of a prediction technique for the analysis and optimisation of the low- and mid-frequency dynamic behaviour of complex vibro-acoustic systems'

Objective: Numerical simulation of vibro-acoustic systems is usually done by finite element or boundary element methods. Both deterministic techniques are based on an element discretization of the problem domain or its boundary surface. The dynamic variables within each element are expressed in terms of simple (polynomial) shape functions, which do not satisfy the governing dynamic equations. These element based methods are well suited for the dynamic analysis of arbitrarily shaped (vibro-acoustic) systems, but their use is practically restricted to low-frequency applications. At higher frequencies, structural and acoustic wavelengths become so small that a prohibitively large number of elements and computational effort would be required to get reasonable prediction accuracy.

In order to extend the applicability of numerical prediction techniques towards vibro-acoustic analysis at higher frequencies, the PMA division has developed a wave based method (WBM). The WBM is a deterministic technique, based on the indirect Trefftz approach. Instead of using locally defined element shape functions, the WBM applies globally defined wave functions, which do satisfy the governing dynamic equations. The vibro-acoustic response of the system at a certain frequency is expressed as a summation of wave function contributions, which result from an integral formulation of the problem boundary conditions. The application of the wave approach to several coupled vibro-acoustic problems has revealed that, compared with element based models, a high prediction accuracy is obtained from substantially smaller wave models, which require less computational efforts. Due to these beneficial convergence properties, the practical frequency limitation of the wave approach is significantly larger than for the element based techniques. Therefore, the wave modelling concept offers an adequate way to comply with the challenge of extending the applicability of deterministic prediction techniques towards higher frequencies. The objective of the proposed research project is the extension of the promising wave modelling concept towards a computationally efficient, generally applicable and easily accessible technique, which provides accurate (coupled) vibro-acoustic predictions in the low- and mid-frequency range.

Period: Jan 2001 – Dec 2004

Contact: W. Desmet, D. Vandepitte, P. Sas

3.2.4FWO Project no.G0161.02: 'Coupled electromagnetic-vibroacoustic modelling of electromagnetic systems”

Partners: RUG – Elektrische Energietechniek, RUG - Informatietechnologie , K.U.Leuven - PMA, K.U.Leuven - ESAT, VUB-WERK

Objective: The project aims at the design and development of reliable vibro-acoustic modeling tools, that are imperative for getting insight in the sensitivity of the noise and vibration levels of electromagnetic systems to various design parameters such as geometry, frequency contents, coolants, structural and acoustic damping, and for extracting design rules for optimal noise control measures.

The forces, resulting from the electromagnetic simulations, will serve as input to numerical models that calculate the mechanical vibration levels in electromagnetic systems, which on their turn will serve as inputs for acoustic radiation calculations. In the first stage of the project, structural finite element models for mechanical vibration calculations will be coupled with acoustic boundary element models for sound radiation calculations. The accuracy and practical limitations of these conventional element based models will be investigated through some numerical-experimental validation cases. The accuracy of element based models is mainly determined by the mesh density. As a consequence, the use of finite element and boundary element models for vibro-acoustic analysis is practically restricted to low-frequency problems. It is therefore expected that these conventional models won’t be able to fully cover the operational frequency range, commonly encountered in electromagnetic systems. In recent years, PMA has been developing a wave based prediction technique, that exhibits a higher computational efficiency than conventional element based techniques and therefore offers an adequate way to perform vibro-acoustic predictions at higher frequencies. Therefore, in a second stage of the project, it will be investigated how this technique can be applied for the vibro-acoustic analysis of electromagnetic systems.

Period: Jan 2002 – Dec 2005

Contact: W. Desmet, W. Heylen

3.2.5Growth Project, GRD1-2001-40674, Noiseless: Reduction of noise emission on machine tools.

Partners: Ideko (ES), Goiti (ES), Fagor Arrasate (ES), Biemmeti (IT), Micromega (BE), Cedrat (FR), KULeuven (BE), WZL (D), Mondragon University (ES), Salomo&Merca (P)

Objective: The objective of this European project is to develop silent machine tools, taking measures over the machine structure, tools and components of punching machines and metal working presses. To attain the objective, innovative concepts in acoustic structural control and active noise control will be used to develop new devices combining passive elements with active components.

The program starts with the identification of the noise sources and transfer paths on the machines. This will be carried out by means of measurements and FEM-simulations. Once these sources are identified, the development of noise attenuation devices will start. This work will be carried out on small-scale experimental set-ups. Then, based on the obtained results, the devices will be re-dimensioned for the large scale machines and evaluated.

Period: Jul 2002 – Jun 2005

Contact: P. Sas, R. Boonen, W. Desmet

3.2.6Hansen Transmissions Project : Research on the dynamics of the drivetrain of a wind turbine.

Partners: Hansen Transmissions (B), , K.U.Leuven (B)

Objective: Wind power is the most advanced and commercially available of renewable energy technologies. In recent years it has been the world’s fastest growing energy source. This expansion involves continually growing wind turbines. The classic concept of the drivetrain causes enormous loads for a power of 3MW. A totally new design is necessary and will change the dynamics of the whole system. Nevertheless the operator wants the power to be guaranteed. The project aims to research the structural integrity and behaviour of a new concept for the drivetrain. In a first period numerical models are built to predict the dynamic behaviour of the system. In a next stage these models will be validated on experimental set-ups. In the beginning the research will focus on the low-frequency domain (structural vibrations). A next task contains the research of the acoustic behaviour of the machine (high-frequency domain). Finally, methods and algorithms for condition monitoring of the wind turbine in operation will be examined and their practical feasibility will be validated.

Period: Sep 2001 – Aug 2004

Contact: D. Vandepitte, P. Sas, J. Peeters

3.2.7IWT project AUT/000252: ACOCAR (Actively COntrolled CAR) : High Bandwidth Computer Controlled Suspensions

Partners: Tenneco Automotive Europe, Monroe European Technical Centre, KULeuven-PMA

Objective: Development of computer controlled active and semi-active vehicle suspensions effective up to frequencies of 30Hz (covering rigid body modes, wheel hop mode, first bending and torsion modes of the body). This includes: the development of control algorithms for semi-active and active suspensions, the development of fast continue variable hydraulic valves, the development of semi-active and active dampers, the development of semi-active and active systems on a test vehicle, the optimal tuning of the controller and/or hardware in lab and on road, the comparison with competitor suspension systems.

Period: Mar 2000 – Mar 2003

Contact: J. Swevers, P. Sas

3.2.8IWT project no. ADV/000163/KUL-TW-MTM-DYS: GRAMATIC, Mixed numerical-experimental vibration analysis for the identification of stiffness and damping properties of layered and graded materials.

Partners: CDM (B), IMCE (B), DDS (B), Bekaert (B), Alliance Europe, LMS (B), Permabond (USA), J.W. Lemmens (B), VUB-MEMC (B), K.U.Leuven-MTM (B), K.U.Leuven-PMA (B).

Objective: For the efficient development and production of layered materials, it is necessary to know the properties of the individual layers. Since there are no methods for the identification of the properties of the individual layers, one is bound to identify these properties directly form measurements on the multi-layered system. However, a generally applicable methodology to achieve this goal has not yet been developed. This is the aim of the GRAMATIC-project: to develop the techniques for identification of the stiffness and damping properties of individual layers, based on the vibration analysis of multi-layer system and using mixed numerical-experimental techniques. These techniques are based on a numerical model of the behavior of specimen, in which the unknown material properties act as model parameters. These model parameters are updated (in an iterative way) in order to achieve correlation between output of the numerical model and the experiment.

Period: Dec 2000 – Dec 2004

Contact: W. Heylen

3.2.9CHASM: coping with health, environmental and safety aspects in standards for machinery.

Partners: K.U.Leuven, Uninversiteit Gent, ULG, WTCM

Objective: European and national standards and legislation force machine manufacturers to control the vibrational and noise emitting behaviour of their machines. In the past, these issues were not so important and consequently no expertise was present in the R&D departments of these companies. Nowadays, controlling these problems is necessary and therefore, the companies need to build up expertise or at least to fall back on expertise present in research institutions.

This project aims to put the sound and vibration expertise of PMA at the disposal of machine manufacturing companies, to apply research results to improve standardisation and to dialog with industry to give direction to the research programs towards technological developments to comply the new standards.

Specifically, the following subjects are treated in the project:

1. 
   prediction methods for sound emission by machines;
   
2. 
   acoustical characterisation of sound sources of fluid flow machines and silencers;
   
3. 
   active noise and vibration control of machines;
   
4. 
   accelerated durability and NVH tests of machine components.
   

Period: Jan 2003 – Dec 2005

Contact: P. Sas, R. Boonen

3.2.10IWT Project TRICARMO: ' Trimmed Car Acoustic Response Modelling”

Partners: K.U.Leuven - PMA, LMS International

Objective: The project deals with the problem of vibro-acoustic modelling of fully trimmed vehicles in the frequency range up to 300 Hz. At present, detailed modelling, as it is required for virtual prototype refinement, is only possible with sufficient accuracy for bare steel car bodies ("body-in-white"). The vibro-acoustic behaviour of the car is however strongly affected by the added finishing components (dashboard, seats…) and surface treatments that are part of the vehicle trim. The innovative objective is to develop accurate and efficient modelling procedures to include the influence of the vehicle trim on the acoustic response in the car cabin. This objective requires an in-depth understanding of the effect of the trim, which will be obtained based on a systematic approach to characterise its behaviour. The project incorporates an extensive experimental work package that allows the identification of the most critical trim components in a car as well as the most important physical properties of the trim. By comparing numerical predictions to experimental data obtained in well-controlled conditions, it will be possible to determine exactly how a certain trim component should be modelled to obtain an acceptable accuracy.

The objective of developing computationally efficient modelling procedures will be reached using two approaches. The first approach is to simplify conventional Finite Element (FE) representations of the trim by developing simplified analytical models. These models take into account the most important parameters of the trim and are used to include the trim by an appropriate set of boundary conditions in an acoustic model of the car cabin. The second approach is to extend the state-of-the-art in vibro-acoustic modelling techniques by developing and implementing a more efficient multi-domain solver and by exploring the potential of a wave based prediction technique. The increased computational performance will permit the use of larger and more detailed FE/BE models, which are currently impractical due to their computational overhead.

Period: May 2003 – Mar 2004

Contact: W. Desmet

3.2.11IWT Project WINDY: ' Flow-induced noise and vibration modelling in the transportation industry”

Partners: K.U.Leuven - PMA, LMS International

Objective: The project aims at the development and validation of numerical tools for flow-induced noise and vibration modelling. On the one hand, it focuses on the applicability of the aero-acoustic analogies of Lighthill and Ffowcs-Williams and Hawkings for industrial applications with subsonic flows such as automotive muffler and exhaust systems and HVAC piping assemblies. On the other hand, it involves the development of modelling approaches for flow-induced vibrations of mechanical structures that confine the considered subsonic flows. An extensive experimental validation program is defined to validate the numerical models and to get insight in the noise generating mechanisms in duct and exhaust systems with uniform as well as with pulsed flow excitation.

Period: Jan 2003 – Dec 2005

Contact: W. Desmet