Image conscious

The structural integrity of welded components could potentially be calculated more easily and accurately with a new residual stress measurement system under development at

, the UK materials technology specialist.

Researchers are developing a technique that uses Digital Image Correlation (DIC) in a simpler way.

DIC is an optical technology for determining residual stress. In a typical DIC process, a high-resolution camera captures a speckled image of a specimen before and after a hole is drilled through it. The images are loaded into a computer and the difference between them is calculated to measure the displacement of the speckles in the image.

The strain on the specimen is obtained from the displacement measurement, and when that information is fed into analytical or finite element models, the residual stress can be calculated.

Residual stress measurement is used to determine the built-in stresses that are often induced in large welded components when they are manufactured. This is widely quantified in industry using the hole-drilling technique, but the method often uses strain gauges to measure the stresses.