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Leiden, Netherlands

Perdahcioglu D.A.,University of Twente | Geijselaers H.J.M.,University of Twente | Ellenbroek M.H.M.,Dutch Space B V | De Boer A.,University of Twente
Structural and Multidisciplinary Optimization | Year: 2012

In light weight structure design, vibration control is necessary to meet strict stability requirements and to improve the fatigue life of structural components. Due to ever-increasing demands on products, it is generally more convenient to include vibration prerequisites in a design process instead of using vibration control devices on fixed designs. One of the main difficulties associated to design optimization of complex and/or large structures is the numerous computationally demanding Finite Element (FE) calculations. The objective of this research is to present a novel strategy for efficient and accurate optimization of vibration characteristics of structures. In the proposed strategy, a sub-structuring method is utilized. The FE model of the complete structure is partitioned, reduced and then reassembled. This increases the computational efficiency of dynamic analyses. Moreover, this method is coupled with a novel reanalysis technique to speed up the repeated structural analyses. These methods are finally embedded in a surrogate-based design optimization procedure. An academic test problem is used for the validation of this novel approach. © Springer-Verlag 2011.

Benthem B.,Dutch Space B V
41st International Conference on Environmental Systems 2011, ICES 2011 | Year: 2011

BepiColombo, one of ESAs Cornerstone missions, is set to launch in 2014 on a journey toward Mercury lasting approximately 6 years. When it arrives in mid 2020, it will gather scientific data during its 1 year nominal mission with a possible 1 year extension and endure exposure up to the equivalent of 10x the solar constant. Leiden-based Dutch Space B.V. is responsible for the Mercury Transfer Module (MTM) Solar Array (SA), which will provide the electrical power required for the transfer to Mercury after the launch by Ariane 5. Part of the testing program concerns the verification of the MTM Solar Array Drive Mechanism's (SADM) ability to cope with the expected heat flows coming from the solar array through the harness and mechanical interfaces. This ability is especially critical during nominal operation in the final stages of the cruise phase at 0.298 AU from the Sun when high heat loads are expected. The SATS was developed and will be delivered by Dutch Space as a dedicated piece of thermal hardware to allow application of representative heat flows into the SADM with 5% uncertainty for ground testing purposes. Mounted on the SADM like the SA, SATS allows well-defined heat loads to be applied to one of three user-selectable interfaces: The spacecraft (through radiation), the SADM pigtail harness and the mechanical interface between SADM and SA (both through conduction). The first is accomplished by having the SATS cylindrical outer casing kept at a uniform temperature to act as a well-defined radiation source, the latter two by using internal MLI in combination with an actively controlled casing temperature to minimize the heat leak from the inside to the environment. The design of SATS is discussed along with an outline of the verification approach. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Kuiper J.M.,Technical University of Delft | van der Heijden R.,Dutch Space B V
Solar Energy | Year: 2011

The development of photo-voltaics over the last decade shows an increase of almost a factor two in efficiency from mono-crystalline silicon to the modern multi-junction solar cells. Recent developments in system optics using concentrators, or splitting up spectral bands through different light paths to different types of solar cells, prove that efficiencies of up to 60-70% are achievable. This significant growth in efficiency of solar arrays, however, increases the focus on lethal electrical biasing incidents. Therefore in this article an inventory of light sources, electrical hazard conditions and solar cell types is provided. Typical solar array sections, voltage bias cases, leakage resistance and light sources are chosen to assess the magnitudes of electrical direct currents. Photometric theory is applied to solar cell assemblies and linked to a simulation model for the electrical performance of solar arrays. This enables a worst case static analysis for the ultimate electrical hazard without any precautions: a wet hand touching a positive connector pin or string endbar in combination with a 'good' electrical grounding of the physical body of the engineer. As a new result, simple equations are derived to estimate the hazard currents for the full scope of solar arrays. The validity to apply these equations is extensively verified by a sensivity analysis over all relevant parameters. © 2011 Elsevier Ltd.

Akcay Perdahcioglu D.,University of Twente | Ellenbroek M.H.M.,Dutch Space B V | Geijselaers H.J.M.,University of Twente | De Boer A.,University of Twente
International Journal for Numerical Methods in Engineering | Year: 2011

A Combined Approximation (CA) based reanalysis technique is proposed for updating the static modes in a reduction basis which can be used for sizing optimization problems. Although the proposed technique is utilized under the framework of the Craig-Bampton (CB) method, it can be employed with any condensation procedure that involves the computation of the static modes. An automated update scheme is also presented that switches the proposed technique with the exact analysis when the computational efficiency is lost. Moreover, the Enriched Craig-Bampton (ECB) method is studied for the reanalysis of the normal modes. The ECB- and the CA-based techniques are merged for efficient update of the CB reduction basis. An academic test problem is utilized for the demonstration of the introduced concepts. © 2010 John Wiley & Sons, Ltd.

Fatemi J.,Dutch Space B V
17th AIAA International Space Planes and Hypersonic Systems and Technologies Conference 2011 | Year: 2011

Finite element modeling and analysis of the thermal protection system (TPS) of the EXPERT re-entry vehicle are presented. Transient heat transfer, non-linear thermomechanical, and thermal buckling analyses were performed to access the thermal and structural response of the TPS under flight aerothermal loads, and to confirm that the design has adequate safety margins. Trajectory-based aerodynamic heating and pressure were applied to the TPS to determine transient temperature response, displacement, stresses, and contact forces due to thermal expansion, thermal strains, and mechanical strains. The analyses results show that the TPS meets all thermal and structural requirements. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

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