The steering committee, Matthew Brake (Rice), Malte Krack (Stuttgart), and Christoph Schwingshackl (Imperial), are seeking 12 graduate students or postdocs to participate in this year’s projects.
Project 1: System Identification of Closely Spaced Modes
Measured data often consists of multi-modal responses; however, existing nonlinear system identification techniques, excluding time-frequency analyses, assume that experimental data is either uni-modal or that the modes are well separated and can be filtered. This project seeks to investigate recent advances in nonlinear system identification for identifying the characteristics of closely spaced modes. This project is part of a larger initiative that spans multiple research camps. At the end of the project, a multi-institutional challenge will be hosted in which test data measured by the ETEST camp at Sandia National Laboratories will be provided with the goal of identifying the modal characteristics of the structure. Results will be compared against other novel techniques being explored both by NOMAD at Sandia National Laboratories as well as other research groups that choose to participate in the challenge.
Project 2: Methods for Strongly Discontinuous Contact Events Based on Time Step Integration
Harmonic Balance is widely used for the vibration simulation of jointed structures. However, it struggles in the case of strongly discontinuous contact events such as recurrent stick-slip or liftoff-collision events of a complete contact area. This and non-periodic processes (chaos; transient loading; shock response) motivate using dedicated methods based on time step integration. The purpose of this project is to assess the current state of the art in this regard for an appropriate test case spanning both recently developed methods and more established approaches. The selected methods will be applied to a three-dimensional model of a beam with a curved tip, undergoing stick-slip interactions with a plate. The technical motivation behind this test case is squeak noise is cars and measurement data is available for qualitative comparison.
Project 3: Monitoring the Interface Behaviour of Bolted Joints
Validating the localized nonlinear contact behaviour of a jointed structure is a challenging task since monitoring the interface during a vibration cycle to identify stick, slip and separation zones, without changing the interface, is very difficult. Total internal reflection has recently been used at ICL to measure the interface conditions of simple, well controlled joints, where two see through interfaces were illuminated via a laser and the reflected/transmitted light from the interface was recorded. The change in reflection/transmission can reveal localised contact zones and show their transition from stick to slip during a vibration cycle. This project will apply the total internal reflection technique to more realistic structures (manufactured prior to the TRC), to obtain for the first time a full picture of the contact conditions during a vibration cycle.