The cost, safety and/or downtime involved in asset or integrity inspections is a major concern for diverse industries, ranging from energy developers through to defence and even geological surveys. Manual inspections are subjective, take a long time and expose humans to risks and hazardous environments.
Digital Image Correlation allows software to objectively detect local changes to the surface or sub-surfaces (if coupled with other techniques) of large civil engineering structures. Dimensional changes can also be detected when using Stereo imaging or laser scanning. NPL has demonstrated this technique to detect changes in rail tunnels and loads on road bridges. Applications also include locating and detecting changes to asset integrity or structure such as cracks on composite surfaces postproduction, paint chipping on coatings, erosion and wear on pipes, corrosion on steel structures, detecting undocumented repairs on structures and insulation damage.
Nick McCormick helped develop a SHM demonstrator based around a concrete footbridge, that was used to investigate accelerated aging and as a test bed for many different types of point sensors. Most recently he has developed NPL’s capability in Digital Image Correlation and uniquely applied it to civil engineering structures like bridges, and even Piers! The latest challenge has been to demonstrate the feasibility of measuring the changes in railway tunnels over time; this has been successfully demonstrated using DIC.
This technique has great potential for use in determining in-plane deformation and also for measuring crack growth and structural deterioration. Work is underway to expand the types of structures that can be analysed and to combine with other measurement types so that measurements of large structures, like tunnels can provide condition information. At the other end of the length scale techniques to allow residual stresses in the first mm of a materials surface are being developed.
Nick has a MA(Cantab) in Natural Sciences and joined the Materials Division at NPL in 1984.
This event is organised by the Retired Members Group.
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