Ultrasonic Non-Destructive Evaluation and structural Health Monitoring (Ultrasonic NDE and SHM)
In Ultrasonic Non-Destructive Evaluation (NDE) and Structural Health Monitoring (SHM), we exploit the propagation of ultrasonic waves to obtain information about a mechanical component. For example, we can determine the mechanical properties of a material (the wave velocity is dependent on the material properties) or detect defects in a component (the present of defect will modify the characteristics of the propagating wave).
We develop new theoretical model to investigate the wave propagation in complex structures and study the interaction with defects, perform advanced numerical modelling using Finite Element analysis, and use the latest experimental techniques to validate the theoretical findings, in order to improve and develop ultrasonic NDE and SHM methods.
Our lab possesses state-of-art equipment:
- Top of the range electronic hardware for linear and nonlinear ultrasonics, with a range of ultrasonic transducers, piezo-actuators and shakers.
- Laser shearography flaw detector
- 1D high frequency scanning laser vibrometer that can be mounted on a de-rotator system (to follow rotating parts), and 1D laser single point laser.
Scanning laser vibrometer (left), for vibration and wave propagation measurement and imaging, de-rotator (centre), to steer the laser beam on a rotating part and measure its vibration, laser shearography (right), to image sub-surface defect.
This equipment allows us to study ultrasonic wave propagation in plate-like structures, sandwich panels, thick components, considering metallic or fibre-reinforced composite materials. We can study the vibration response of panels but also the vibration of blades during rotation.
In NDE and SHM, the early detection and characterisation of structural damage is critical for eﬀective structural integrity management. Therefore, we are investigating the use of nonlinear ultrasonic methods for detecting various forms of material and structural damage earlier than can be achieved by conventional linear ultrasonics.
The interaction of a propagating wave with a crack-like defect may generate new frequencies (higher harmonics or sidebands) due to the nonlinear clapping motion of the defect. These new frequencies can be used to obtain information about the defect. We are now focussing on understanding the fundamental mechanisms involved in the nonlinear ultrasonic response and developing innovative techniques to exploit this response to detect and characterize damage without the need of a baseline comparison.
For example, the use of the nonlinear ultrasonic response allows one to image the closed part of a crack, which is not possible with the conventional linear approach.
Linear (left) and nonlinear (right) baseline-free imaging of a partially closed crack
This research forms the basis for the design of generic methodologies for non-linear ultrasonic measurement systems that can reliably detect delaminations and debonding in composite laminates, or fatigue damage in additively manufactured material, and therefore provides significant benefits in improving the greater uptake of these material in a wide range of industries.