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Farkas L.,Lms International | Moens D.,De Nayer Institute | Donders S.,Lms International | Vandepitte D.,Catholic University of Leuven
Mechanical Systems and Signal Processing | Year: 2012

This paper deals with the design and optimisation for crashworthiness of a vehicle bumper subsystem, which is a key scenario for vehicle component design. The automotive manufacturers and suppliers have to find optimal design solutions for such subsystems that comply with the conflicting requirements of the regulatory bodies regarding functional performance (safety and repairability) and regarding the environmental impact (mass). For the bumper design challenge, an integrated methodology for multi-attribute design engineering of mechanical structures is set up. The integrated process captures the various tasks that are usually performed manually, this way facilitating the automated design iterations for optimisation. Subsequently, an optimisation process is applied that takes the effect of parametric uncertainties into account, such that the system level of failure possibility is acceptable. This optimisation process is referred to as possibility-based design optimisation and integrates the fuzzy FE analysis applied for the uncertainty treatment in crash simulations. This process is the counterpart of the reliability-based design optimisation used in a probabilistic context with statistically defined parameters (variabilities). © 2011 Elsevier Ltd. Source

Moens D.,De Nayer Institute | Hanss M.,University of Stuttgart
Finite Elements in Analysis and Design | Year: 2011

The objective of this paper is to give a general overview of recent research activities on non-probabilistic finite element analysis and its application for the representation of parametric uncertainty in applied mechanics. The overview focuses on interval as well as fuzzy uncertainty treatment in finite element analysis. Since the interval finite element problem forms the core of a fuzzy analysis, the paper first discusses the problem of finding output ranges of classical deterministic finite element problems where uncertain physical parameters are described by interval quantities. Different finite element analysis types will be considered. The paper gives an overview of the current state-of-the-art of interval techniques available from literature, focussing on methodological as well as practical aspects of the presented methods when their application in an industrial context is envisaged. Their possible value in the framework of applied mechanics is discussed as well. The paper then gives an overview of recent developments in the extension of the interval methods towards fuzzy finite element analysis. Recent developments in the framework of the transformation method as well as optimisation-based procedures are discussed. Finally, the paper concentrates specifically on implementation strategies for the application of the interval and fuzzy finite element method to large FE problems. © 2010 Elsevier B.V. All rights reserved. Source

Van Hooreweder B.,Catholic University of Leuven | Moens D.,De Nayer Institute | Boonen R.,Catholic University of Leuven | Sas P.,Catholic University of Leuven
International Conference on Noise and Vibration Engineering 2012, ISMA 2012, including USD 2012: International Conference on Uncertainty in Structure Dynamics | Year: 2012

This work describes the design, implementation and first results of a fatigue test rig capable of subjecting cylindrical specimens of different sizes and materials to complex real-life loading conditions. The resulting test rig can be used to combine a rotating bending load with a fluctuating torsional load. Due to a closed electromechanical loop, power consumption is limited and a maximum test frequency of 50Hz can be obtained for both the bending and the torsion. In addition, the optimal control strategy is determined using analytical techniques in order to simulate the test rig and to further reduce the power requirements for both electrical motors. Bending moments of 5-150 Nm can be combined with torsional moments of 5- 100 Nm at test frequencies between 2 and 50 Hz, leading to a significant advantage with respect to conventional fatigue testing techniques. In general, the presented test rig concept allows accelerated multi-axial fatigue tests on steel specimens, leading to a reduction of the time and cost needed for experimental validation of analytical and numerical fatigue calculations. Additionally, multi-axial fatigue criteria will be studied for different specimen sizes, geometries and materials. Furthermore, the test rig concept consists of conventional mechanical components making it relatively straightforward to implement and economically feasible. © (2012) by the Katholieke Universiteit Leuven Department of Mechanical Engineering All rights reserved. Source

Mareckova K.,Rotman Research Institute | Mareckova K.,University of Nottingham | Mareckova K.,Masaryk University | Chakravarty M.M.,Rotman Research Institute | And 15 more authors.
Brain Structure and Function | Year: 2015

We used magnetic resonance (MR) images obtained in same-sex and opposite-sex dizygotic twins (n = 119, 8 years of age) to study possible effects of prenatal androgens on craniofacial features. Using a principal component analysis of 19 craniofacial landmarks placed on the MR images, we identified a principal component capturing craniofacial features that distinguished females with a presumed differential exposure to prenatal androgens by virtue of having a male (vs. a female) co-twin (Cohen’s d = 0.76). Subsequently, we tested the possibility that this craniofacial “signature” of prenatal exposure to androgens predicts brain size, a known sexually dimorphic trait. In an independent sample of female adolescents (singletons; n = 462), we found that the facial signature predicts up to 8 % of variance in brain size. These findings are consistent with the organizational effects of androgens on brain development and suggest that the facial signature derived in this study could complement other indirect measures of prenatal exposure to androgens. © 2014, Springer-Verlag Berlin Heidelberg. Source

Jacobs W.,Catholic University of Leuven | Boonen R.,Catholic University of Leuven | Sas P.,Catholic University of Leuven | Moens D.,De Nayer Institute
Mechanical Systems and Signal Processing | Year: 2014

This paper experimentally investigates the formation of a lubricant film in a deep groove ball bearing and its effect on the bearing dynamics. A novel test rig is introduced, which allows testing different types and sizes of bearings in real-life conditions. The test rig dynamics are optimised such that the dynamic properties of the bearing are measured in a frequency range below the resonances of the flexible modes. Two properties of the bearing, both its stiffness and damping value in the direction of the static bearing load, are identified. The behaviour of the lubricant film between the rolling elements and raceways is measured based on the electrical resistance through the bearing. For this purpose, the bearing housing is electrically isolated from the surrounding structure. The electrical resistance, stiffness and damping of the test bearing are identified during a speed run-up. The influence of the bearing temperature is analysed as well. During a run-up at constant bearing temperature, the measurement of the electrical resistance describes the formation of the lubricant film. Due to the formation of the lubricant film, the bearing stiffness increases by 3.2% while the damping increases by 24%. During a warm-up of the bearing, the viscosity of the lubricant film decreases strongly. A resulting decrease in electrical resistance, stiffness and damping is measured. Finally, the electrical resistance, stiffness and damping are identified at different speeds, after the bearing has reached a stable temperature at each speed. A combined effect of both rotation and temperature is observed and discussed. © 2013 Elsevier Ltd. All rights reserved. Source

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