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The University of Southampton
Engineering

Research project: Ultrasonic Removal of Surface Accretions

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Exposed surfaces can accumulate deposits such as dirt, scale and marine organisms. A safety-critical example is in-flight ice accretion on aircraft wings for which a high power preventative solution (hot air bleed from the engines or electric heater elements) is required to melt the ice and avoid catastrophic failure. This project is investigating the feasibility of debonding various accreted layers from host structures using high frequency (ultrasonic) vibrations.

When structural waves are made to travel through a host structure to which a layer of accreted material is attached, shear stresses are generated at the interface. Debonding of the layer will occur if the interface stresses are sufficiently large. The levels of stress generated depend not only on the level of excitation but also on other factors such as frequency, type of wave, actuators (number, type and placement) and material properties of the accreted substance. In order to assess the feasibility of debonding accretions in this way a physical model is required which is capable of predicting wave propagation in multilayered structures, and the stresses that arise, due to the deployment of a particular actuator.

We have implemented a Semi-Analytical Finite Element (SAFE) model of a multilayered structure where the various levels represent the host structure, an accreted material and/or a piezoelectric material for actuation. The SAFE method enables computationally efficient and physically insightful modelling of an infinitely long uniform structure of arbitrary cross section from a detailed Finite Element model of just the 2-D cross section. A wave-based model of a structure with a short piezoelectric patch and localised accretion can be assembled from several infinite models. This modelling framework is potentially able to predict stress distrubutions at any position along the structure when an array of piezoelectric actuators is driven by arbitrary electrical signals.

Experiments have been carried out to demonstrate removal of plaster from an aluminium plate in the laboratory and removal of ice from a wing model in a wind tunnel.

Wave types are categorised e.g. according to direction of particle motion
Ultrasonic waves in a plate
Stresses arising from passage of ultrasonic waves
Shear stresses at an interface
Beam with accretion and actuator
Beam with accretion and actuator

Related research groups

Dynamics Group

Key Publications

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