Browsing by Author "Lancereau, Damien"

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    Fundamental Research
    (Cranfield University, 2017-11-15 12:01) Lancereau, Damien
    Digital image presented at the 2017 Defence and Security Doctoral Symposium.On this picture: My supervisor (Hugh Goyder) and me, in front of my experimental workbench. This image presents two generations of researchers. It reminds us of the continual evolution of the sciences. Behind, the metal frame isolates the suspended test items from ambient vibration. The two large cast iron beds minimize the transmission of ground vibration (car traffic seismic, steps). A beam is suspended by two almost invisible fishing wires from the frame; it is ready for vibration testing. With this setup, it is possible to do fundamental research on the dynamics of built-up structures. Our goal is to understand what is happening inside a connection between two parts of the beam during vibration.
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    How to Predict the Vibration Energy Dissipation of Bolted Joint?
    (Cranfield University, 2017-12-13 16:19) Lancereau, Damien
    3MT presented at the 2017 Defence and Security Doctoral Symposium.The objective of this PhD is to investigate and understand the dynamics of joints in built-up structures. Currently, we do not understand the influence of the joints on the damping or the stiffness of a system. Our work will try to improve the quality of dynamics in finite element simulations. The aeronautic industry is currently limited in there design by the lake of dynamic joint model. For example, a problematic joint on the wing of the new Airbus A380 cost around one billion pounds to the company. Our approach is to start by focusing on experiments. We excite a structure and measure the response. Currently, we are investigating a two layer sandwich beams connected by bolts, which is already complex. The main challenge is the nonlinearity of built-up structures. To understand it, we decompose the response signal into different resonance modes, and then we fit short intervals of the signal to a mathematical model. This method gives time varying parameters which are simple to interpret. For example, a measurement of the size of a contact patch has been obtained from the shift in natural frequency. Also, measurements of the damping when correlated with measurements using a pressure film provided an insight of the position of the micro-friction interfaces in the system. And the use of shims in the interfaces allowed a better understanding of the interface.