Professor Paul Wilcox, Bristol

Recent advances in ultrasonic imaging for non-destructive evaluation
When Feb 09, 2015
from 02:00 PM to 03:00 PM
Where LR8, IEB Building, Engineering Science
Contact Name
Contact Phone 01865-273925
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ABSTRACT: Quantitative Non-Destructive Evaluation (NDE) is essential for ensuring the safe operation of safety-critical structures. NDE invariably exploits the interaction of material anomalies with some form of wave, whether the wave be elastic, electromagnetic, optical or thermal. Of these, elastic waves usually in the 1-10MHz ultrasonic range and x-rays are the only modalities that can penetrate the interior of common engineering materials. Computed x-ray tomography remains the gold standard against which other NDE techniques are often compared, but it cannot be applied in situ. Increasingly stringent health and safety requirements also mean that single-exposure x-ray techniques are becoming less popular for in situ inspection. Hence, there is a drive to exploit ultrasonic elastic waves to extract more and more information about the interior of a structure. In this talk, I will focus on several developments using ultrasonic arrays. I will show how modern instrumentation allows the diffraction limit of resolution to be reached and, in some cases exceeded. Extensions to "difficult" materials such as carbon-fibre composites will also be examined. Classical ultrasonic NDE is based on linear elasticity, but elastic nonlinearity is well known to be extremely sensitive to the early stage of material degradation processes such as fatigue and creep. This regime is of critical importance to operators of ageing plant but measurement of elastic nonlinearity is notoriously diifficult. I will show initial results from a new technique, which has the potential for imaging elastic nonlinearity within the interior of a component.