Guide
What is digital image correlation?
DIC measures how a surface deforms by watching a random speckle pattern applied to it. Software tracks small patches of that pattern from frame to frame, and from how they move and stretch it computes displacement and strain across the whole surface at once, rather than at the single line a strain gauge or clip gauge would give you.
Also called: DIC, digital image correlation, optical strain measurement, non contact strain, full field strain, speckle pattern strain, video gauge, optical extensometer, non contact extensometer, strain mapping
How it works
Two cameras viewing from different angles give 3D, or stereo, DIC, which captures out of plane movement as well. One camera gives 2D, which is fine for flat specimens that stay flat.
What to check before you buy
- 2D or 3D. If the part bends out of plane at all, you need stereo.
- Field of view and standoff, which set what magnification you are working at.
- Strain resolution and accuracy, quoted for a stated field of view.
- Sampling rate, and whether it must sync with a load frame.
- Speckle pattern requirements. The pattern is part of the measurement, and a bad pattern ruins good hardware.
- Integration with an existing Instron or MTS frame and its data acquisition.
Published free, no form. If a supplier will not answer one of these in writing, that is worth knowing before you order.
Common confusion
A video extensometer is the simpler relative: it tracks two marks and gives you extension, replacing a clip gauge without touching the specimen. DIC gives you the whole field, including where a crack is about to start.