Steve Sharples

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Steve sharples 2011.jpg

Senior Research Fellow, Applied Optics Group

Phone: +44 (0)115 95-15220 (6th floor office), which rings through to +44 (0)115 84-67892 (2nd floor research office)

Location: Tower 606, Tower 202

Email (@nottingham.ac.uk): steve.sharples

Previous research

I've worked in the field of laser ultrasonic research since 1997, and obtained my PhD, "All-Optical Scanning Acoustic Microscope" from the University of Nottingham in 2003. My research has centred around using novel laser ultrasonic techniques for materials characterisation and nondestructive evaluation (NDE). This has involved developing new techniques, new instrumentation, and new insights into the interaction of acoustic waves with materials. During the course of my PhD I improved the instrumentation to such a degree that for the first time we were able to take images – rather than single point measurements – of surface acoustic waves (SAWs) which were generated and detected using lasers. This improvement in the instrumentation led to an area of research on "Adaptive laser ultrasound with programmable optical field distributions" (2000-2003), which had profound implications for ultrasonic testing integrity. This was the study of the deleterious effects of anisotropy and microstructure on the propagation of ultrasound, and improving the methods and mechanisms to model, measure, analyse and predict this behaviour. Demonstrations of these effects led to revelations amongst many industrial (and some academic) collaborators, as it explained beautifully some of the phenomena (including unreliable data) that they had been seeing.

Success in this initial work led directly to a Core Project in the new Research Centre for NDE, formed in April 2003, titled "NDE of Difficult Materials" (2003-2007). My work here used the understanding of acoustic aberration to develop techniques in three key areas. (1) Using the information gained from the effects of acoustic aberration to infer statistical properties (mean grain size, degree of anisotropy) of the material under investigation. (2) Acoustic aberration correction, whereby the aberration is detected using a multi-channel acoustic detector which I had developed, and applying correction to the generation pattern. This cancels out the effects of the microstructure, giving greater confidence and clarity for the detection of defects. (3) Development of a new technique I termed "spatially resolved acoustic spectroscopy" (SRAS) which is capable of imaging microstructure, crucial for estimating likelihood of structure-sensitive failure mechanisms. Matt Clark and I are joint inventors on the patent for this technique.

From 2007-2008 I worked on a project entitled "Advanced ultrasonic techniques for highly scattering ordered and semi-ordered materials", which involved developing techniques for rationalising the amount of information necessary to determine key properties of these complex materials (such as degree of randomness, or porosity).

Current research

I am the principal researcher working on the RCNDE Core Project, "Laser ultrasonics for the detection of damage precursors" (2008-present). Conventional (linear) ultrasonics is very poor at detecting changes in the material structure of a component which have an influence on its working life, prior to the formation of measurable cracks and dislocations. New techniques are being developed in order to study the relationship between fatigue and the material elastic nonlinearity – a deviation from Hooke’s Law, which describes a linear relationship between stress and strain. Although these nonlinear ultrasonic techniques are potentially much more sensitive than linear methods, measurable changes are several orders of magnitude smaller than the equivalent changes in the linear response, so they are tricky to implement.

I am the principal investigator on a 2.5 year emda (East Midlands Development Agency) and Rolls-Royce funded Technology Demonstrator project, to develop the SRAS instrumentation for materials characterisation (1 April 2010 - 31 October 2012). This has involved reducing the size of the SRAS instrument from one which takes up an entire optical bench, to one where all the optics could fit inside a shoebox. The instrument will gain the ability to scan rough surfaces, and the lateral resolution will be pushed down below 25 microns.

I am the researcher on Matt Clark's Let Nano Fly! micro-project entitled, "Complex near-field optics placed by AFM as an enabling technology for nanoSRAS inspection", or nanoSRAS for short, which will begin soon and run over a period of 4 months (part time, equivalent to 2.5 months).

Where to find me

  • 202 - Applied Optics Research Lab - 84-67892
  • 303 - ARRO-SAM Lab - 95-15638
  • 306 - O-SAM Lab/Ultrasonics Labs foyer - 95-15386
  • 307 - Nonlinear Lab - 95-15615
  • 606 - My office - 95-15220

Other activities and responsibilities

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