Combination of Digital Image Correlation and Thermography

Ther­mog­ra­phy is based on the prin­ci­ple that induced heat in mechan­i­cal com­po­nents caus­es a dif­fer­ent tem­per­a­ture field in the area of defects or inho­mo­geneities. The dig­i­tal image cor­re­la­tion is a pow­er­ful sys­tem for mea­sur­ing and visu­al­iz­ing strain, defor­ma­tion and 3D sur­face shape.

The VIC-3D IR Sys­tem fea­tures an infrared (IR) cam­era that is inte­grat­ed with the DIC cam­eras enabling tem­per­a­ture data to be accu­rate­ly acquired and ana­lyzed with the full-field strain and defor­ma­tion data. The sys­tem works by first cal­i­brat­ing the intrin­sic opti­cal para­me­ters of the IR cam­era and then cal­i­brat­ing the posi­tion of the IR cam­era rel­a­tive to the stereo DIC sys­tem. This tri­an­gu­la­tion allows VIC-3D to place the ther­mal and strain (or defor­ma­tion) as well as 3D sur­face data into a com­mon coor­di­nate system.

The cal­i­bra­tion pro­ce­dure has been stream­lined by inte­grat­ing the IR cam­era into our VIC-Snap image acqui­si­tion soft­ware, which allows the user to cap­ture images from the IR and DIC cam­eras simul­ta­ne­ous­ly. The result is an easy to use turn-key ther­mal imag­ing sys­tem that uti­lizes dig­i­tal image cor­re­la­tion to accu­rate­ly mea­sure tem­per­a­ture and strain con­cur­rent­ly with­out any con­tact with the sam­ple. Ther­mal and strain data can be viewed, ana­lyzed, and extract­ed over the entire field or at pre­cise locations.

The sys­tem is sold as a turn-key solu­tion which includes all soft­ware, hard­ware, onsite instal­la­tion, and one year of unlim­it­ed tech­ni­cal sup­port and soft­ware upgrades giv­ing you piece of  mind that your sys­tem func­tions as intend­ed, so you can start acquir­ing data imme­di­ate­ly. This unique ther­mal inte­gra­tion capa­bil­i­ty may also be added to any exist­ing VIC-3D sys­tem for increased functionality.

System Configuration and Features

Both the IR cam­era for ther­mog­ra­phy and the two CCD cam­eras for 3D image cor­re­la­tion are mount­ed on a stan­dard stereo bar.

  • Tem­per­a­tures up to 2,000C
  • Syn­chro­nized IR and DIC images
  • User-friend­ly set­up and calibration
  • Unique­ly designed IR cal­i­bra­tion targets
  • Ana­log data synchronization
  • Extract points, regions, or node loca­tions for FEA validation
  • Accu­rate­ly mea­sure defor­ma­tion and ther­mal data concurrently
  • Remote­ly view and acquire images using the Vic-Snap remote
  • Mea­sure 3D full-field dis­place­ments and strains
  • All the fea­tures for the VIC-3D sys­tem included


Advan­tages of this mul­ti-func­tion device are all appli­ca­tions with com­po­nent defor­ma­tions caused by ther­mal ener­gy like cur­rent flow. This prod­uct allows a simul­ta­ne­ous­ly deter­mi­na­tion of the heat flows as well as strain and deformation.


Example 1: Photovoltaic Module

Defec­tive pho­to­volta­ic mod­ules have been mea­sured dur­ing oper­a­tion over sev­er­al min­utes.  A prepa­ra­tion with speck­le pat­tern is nec­es­sary for dig­i­tal image cor­re­la­tion (here the back­side of the pan­el). The marked areas are heat­ed up due to electric/mechanical errors dur­ing operation.


Prin­ci­pal strain (epsilon 1) over time (index) of the points C0, C1, C2 shown in the image below. Fol­low­ing three dimen­sion­al pre­sen­ta­tion of the tem­per­a­ture values.



Three dimen­sion­al graph of the con­ture, super­posed with the mea­sured tem­per­a­ture (colour scale).



Three dimen­sion­al graph fo the con­ture, super­posed with the strain mea­sure­ment (colour scale).


Example 2: Analysis of simultaneous one-sided heating and compressive loading on an e‑glass/vinyl ester/ balsa wood sandwich composite sample

Under­stand­ing ther­mo-mechan­i­cal behav­ior of mate­r­i­al can be a vital com­po­nent when design­ing vehi­cles  and struc­tures that may become exposed to high tem­per­a­tures. Vir­ginia Tech’s Extreme Envi­ron­ments, Robot­ics, and Mate­ri­als (ExtReMe) Lab­o­ra­to­ry focus­es on the impact of extreme envi­ron­ments on mate­ri­als. This includes research that is focused on under­stand­ing the ther­mo-mechan­i­cal behav­ior of mate­ri­als both dur­ing and fol­low­ing fires. Exper­i­men­tal inves­ti­ga­tions are per­formed to under­stand the evo­lu­tion of the mate­r­i­al due to ele­vat­ed temperature.

The senior research asso­ciates in the lab used the VIC-3D IR sys­tem to find the effects of a simul­ta­ne­ous one-sided heat­ing and com­pres­sive load­ing test on an e‑glass/vinyl ester/balsa wood sand­wich com­pos­ite sam­ple. As one researcher stat­ed, “The VIC-3D IR sys­tem identied sev­er­al tran­sient events dur­ing the com­pres­sion tests which would not have oth­er­wise been ful­ly under­stood using either DIC or IRT inde­pen­dent­ly. Through this test­ing, sev­er­al fea­tures of sand­wich com­pos­ite ther­mo­me­chan­i­cal behav­ior  were elu­ci­dat­ed which would not have been pos­si­ble with tra­di­tion­al point mea­sure­ments (e.g. strain gages, defec­tome­ters, or thermocouples).”

Image above: Analy­sis of simul­ta­ne­ous one-sided heat­ing and com­pres­sive load­ing on an e‑glass/vinyl ester/ bal­sa wood sand­wich com­pos­ite sam­ple, Iden­ti­fy­ing sev­er­al tran­sient events, which  would  not  have been  ful­ly  under­stood  (stat­ed by the engin­ners of Vir­gina Tech´s ExtReMe Lab­o­ra­to­ry) using  either  DIC  or  IRT inde­pen­dent­ly or only apply­ing tra­di­tion­al  point  mea­sure­ments  (e.g.  strain gages, deec­tome­ters, or ther­mo­cou­ples).  Source:  Vir­gina Tech´s ExtReMe Laboratory