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contentsMicroscopyandAnalysis | July/August 20175eueu

profile6AMJuly/August 2017 | MicroscopyandAnalysisAn X-ray visionFrom word go, Professor Phil Withers, Regius Professor of Materials at the UK-based University of Manchester, had a passion for the practical. As a child, he spent a lot of time repairing things, and in his words: "There is a certain satisfaction in understanding how something functions and making it work again, and I don't think I've ever lost that."Drawn to the physical world, he studied the Natural Sciences at the University of Cambridge from 1982, finally specialising in Physics. Realising he simply wasn't interested in 'quarks and far-off galaxies', he opted for a PhD in metal matrix composites.During his doctorate, he spent his Summers at the Risø National Laboratory in Denmark, using neutron diffraction to measure the stresses in each phase within the composites."It was quite exciting to do an experiment inside a nuclear reactor," he recalls. "And in many ways some of my happiest days were cycling from the neutron reactor to the physics department, with a floppy disc the size of an old LP under my arm, thinking I'm actually being paid to do this work."Withers' excitement for practical Materials Science has continued ever since. On finishing his PhD, he accepted a lectureship at the University of Cambridge, where he continued to work with short-fibre metal matrix composites. Crucially, at the time, the young researcher was also spending a lot of time at the UK-based neutron source, ISIS, Rutherford Appleton Facility, measuring the stresses and strains in these composites.Working with a pan-European team of researchers, including colleagues from ISIS as well as the Fracture Research Group at the Open University, he designed and built the world's first instrument to measure engineering strain using neutron diffraction. Dubbed ENGIN, the strain scanner – a time-of-flight neutron diffractometer – used large radial collimators with detector arrays to quickly measure precise elastic strains within small volumes of bulky specimens.For the first time, researchers were able to quickly map residual stresses in 3D in large engineering materials and components.As Withers highlights: "The instrument really sped our research up, we no longer had to waste time setting up experiments and it massively improved the accuracy and rate at which we could work." ENGIN has since served as a blueprint for engineering instruments worldwide, mapping stress fields. And as the researcher points out: "Strain measurements are now taking place all around the world, based on our instrument." Come 1998, and with composite research continuing apace, Withers was offered a Professorship at the Manchester Materials Science Centre. As he puts it: "I loved Cambridge but I do think that some degree of movement is good for you, and the time was right to move on."Failure and stressAt Manchester, he set to work establishing the Unit for Stress and Damage Characterisation, using neutron, and later, Raman and X-ray analysis to primarily understand why materials fail."To [understand materials failure], you need to be able to know the externally applied stresses, the internal residual stresses and the defects within the materials," says Withers. "At this point, I got really interested in using synchrotron X-ray diffraction, to measure the residual stresses, and also X-ray imaging, to find the defects," he adds. "Synchrotron sources are so much brighter than laboratory. X-ray sources meaning we could collect the information so much quicker."As Withers' enthusiasm for X-ray analysis grew, the researcher was also working with the likes of Rolls Royce and BP to better understand how residual stresses in components can cause unexpected, and sometimes catastrophic, failure."If a door handle fails it's frustrating but if an aircraft engine fails, that's In his relentless quest to understand why materials fail, Professor Phil Withers has pioneered the use of neutron and X-ray beams to map stresses and image components. Rebecca Pool reports