Principle of Digital Image Correlation

Digi­tal Image Cor­re­la­ti­on (often refer­red to as “DIC”) is an easy to use pro­ven opti­cal method to mea­su­re defor­ma­ti­on on an object sur­face. The method tracks the gray value pat­tern in small neigh­bor­hoods cal­led sub­sets (indi­ca­ted in red in the figu­re below) during defor­ma­ti­on. Digi­tal Image Cor­re­la­ti­on has been pro­ven over and over to be accu­ra­te when com­pa­red to valid FEA models. The com­mer­cial­ly avail­ab­le VIC-2D and VIC-3D sys­tems from Cor­re­la­ted Solu­ti­ons both uti­li­ze this advan­ced opti­cal mea­su­re­ment technology.

 

Digital Image Correlation Overview

Below are the rea­sons why its ver­sa­ti­li­ty, robust­ness, and ease of use make it the only choice when it comes to digi­tal image correlation.

DIC - Principle of Digital Image Correlation

Two-dimensional Example

In the two pic­tures below you can see a speck­le pat­tern on an alu­mi­num sam­ple with two off­set semi-cir­cu­lar cut-outs. The two pic­tures were taken from an ani­ma­ti­on with the left image taken from the begin­ning and the right pic­tu­re taken from the end of the ani­ma­ti­on. Sin­ce the defor­ma­ti­on is pre­do­mi­nant­ly in-pla­ne, a sin­gle came­ra can be used to mea­su­re the deformation.

VIC2D

Small Defor­ma­ti­on

VIC2Da

Lar­ge Deformation

The pic­tures below show the hori­zon­tal strain mea­su­red by two-dimen­sio­nal image cor­re­la­ti­on for the pic­tures shown above.

VIC2D-2 VIC2D-2a
VIC2D-2b


Three-dimensional Example

The­se two speck­le images below were taken simul­ta­ne­ous­ly with the left and right came­ra of a ste­reo-sys­tem. The sam­ple its­elf is a pie­ce of glass with the com­pa­ny logo sti­cker adhe­red to the sur­face.  The speck­le pat­tern was app­lied using stan­dard off-the-shelf flat white and black spray paint.  Can you make out the shape?

VIC3Dleft
Left View
VIC3Dright
Right View

In the plot below the shape of the logo sti­cker mea­su­red with the VIC-3D Sys­tem is shown. The thic­kness of the logo sti­cker is appro­xi­mate­ly 0.003″ or 0.070mm.

VIC3D-2
For more info­ma­ti­on have a look at our DIC pro­ducts or con­ta­ct us via info@isi-sys.com or +49 561 — 739798–0