Professor Gaëtan Kerschen's project is one of 12 projects selected for funding by the WEL-T Investigator programme (WEL Research Institute). It aims to develop a new generation of vibration tests capable of rigorously and robustly capturing the very real non-linear behaviour of aerospace structures.
I
n modern engineering, aircraft, turbomachinery and satellites are first designed and optimised digitally. But for these models to be reliable, they must be validated experimentally. However, current testing methods are based on the assumption that the structure behaves linearly, i.e. that its response is proportional to the excitation. "In reality, many aerospace structures exhibit marked non-linearities, explains Professor Gaëtan Kerschen, an aerospace and mechanical engineer. I am thinking in particular of play in assemblies, contacts, friction, joints, flexible elements, etc. These effects can profoundly alter the vibrational response, even leading to multiple or unstable behaviours that conventional methods fail to capture."
With his project, Gaëtan Kerschen aims to bridge this gap between advanced numerical simulations and experimental testing by proposing specific methods for non-linear systems. "Current vibration methods mostly operate in an open loop," explains the researcher. "This means that an excitation signal is applied, the response is observed, and then the data is analysed. In this scenario, unstable behaviours remain inaccessible, and the exploration of dynamics is limited."
The project proposes working in a closed loop using feedback loops to stabilise unstable orbits that cannot normally be observed in tests, and using continuation techniques to systematically explore the dynamics of the system (ramifications, jumps, bifurcations, etc.) without first requiring a detailed mathematical model.
The CHEOPS satellite is mounted on a longitudinal shaker that forces it to vibrate at different frequencies. At the beginning of the test, performed at RUAG Space in Zurich, Switzerland, low-frequency sine-wave vibrations of 5 Hz are applied. As the test progresses, a sweep, using sine waves of increasing frequency, is performed up to the maximum of 100 Hz.
From fundamental research to commercialisation
This project complements perfectly his ERC ENTIRE project, which began in September. With the Wel-T Investigator programme, the researcher has chosen to focus more specifically on aspects directly related to the commercialisation of these cutting-edge results.
Wel-T is interested in transforming research into concrete solutions for industry. In this context, the funding will make it possible to strengthen the robustness, efficiency and versatility of the experimental continuation algorithm, adapt it to the constraints of real-world testing, particularly in highly instrumented environments such as aerospace test benches, and define a standardised, documented and industrialisable methodology that goes beyond the academic laboratory setting.
Ultimately, this project aims to change standard vibration qualification practices so that "instead of ignoring or circumventing non-linearities, engineers will have tools to measure, understand and integrate them into their digital models."
