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

dic-thermografie

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