Special MSE Colloquium with Michael Fitzpatrick
Date: October 31, 2014 from 11:00 am to 12:00 pm EDT
Location: Columbia University, Morningside Campus
S.W. Mudd, Room 214
Contact: For further information regarding this event, please contact APAM Department by sending email to seasinfo.apam@columbia.edu or by calling 212-854-4457.
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Prof. Mike Fitzpatrick
Lloyd's Register Foundation Chair in Materials Fabrication and Engineering, Coventry University, UK

"Residual Stresses in Materials: why they matter for Structural Integrity, and how to measure them"

Residual stresses are those stresses that exist in a material or a component as a result of its fabrication. They can be caused by forming deformations, heat treatment, welding, surface treatment, and fit-up forces. In service, residual stresses can lead to premature failure, or, conversely, can be deliberately introduced in order to increase life and maintain structural integrity. Tensile residual stresses associated with welding can lead to stress corrosion cracking, for example, whilst peening methods from shot peening to laser shock peening can introduce beneficial compressive residual stress. There are many examples of engineering failures where residual stress was in some way a contributory factor.

This talk will review some of the key concepts around residual stress, and will illustrate the range of experimental methods that can be used for their determination. All the available experimental techniques have advantages and limitations, and selection of the correct process, with appropriate validation, is an important skill for those concerned with the analysis and consequences of residual stresses. There is increasingly a trend towards modelling of residual stress effects, often with incomplete or incorrect material data, and the use of a single measurement technique, selected for convenience rather than because it is the most informative method to use.

The talk will be illustrated with examples from a range of industries. In recent years, advanced non-destructive techniques such as neutron and synchrotron X-ray diffraction have been used alongside novel destructive methods such as the contour method and deep-hole drilling for the study of problems relevant to the nuclear and aerospace industries: both industries are highly-safety-critical and heavily regulated, and there are severe consequences for in-service failures.

There are many examples of residual-stress-driven problems in automotive, marine, and other sectors where knowledge of the residual stresses would be of great value, but the drive towards cost containment means that even when a problem is identified as having a residual stress origin, there is neither the resource nor the in-house expertise to be able to tackle it appropriately. With the ongoing improvement in experimental and analytical techniques, we are now at the point where residual stress measurements can be more widely accessed and given correct interpretation.

Prof. Fitzpatrick is the Executive Dean of the Faculty of Engineering and Computing at Coventry University, and also holds the Lloyd's Register Foundation Chair of Materials Fabrication and Engineering. He is a Chartered Engineer, a Chartered Scientist, and a Fellow of the Institute of Materials, Minerals and Mining.

His research centres around the application of advanced experimental methods to materials engineering applications, particularly in the nuclear power and aerospace industries. His group has a range of research projects assessing materials performance and structural integrity issues in collaboration with partners in industry and government research laboratories around the world, including Airbus, Alcoa, and the US Air Force Research Laboratories. He leads the L1.7M EPSRC PROMINENT consortium researching metallic materials for nuclear fission applications, and is a partner in the new International Joint Research Centre on Nuclear Safety funded by the Lloyd's Register Foundation.

His recent interests include the study of laser shock peening for life enhancement of aerospace and marine structures, and components in nuclear power plant. He also works on and the development of novel structural concepts such as bonded crack retarders for improving airframe structural integrity. Mike has been a user of the international neutron and synchrotron X-ray facilities for over 20 years, for the study of internal stress and damage development in metallic materials and components. He has published over 150 research papers and has successfully supervised 24 PhD students to completion.

Host: I.C. Noyan