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Shearography / ESPI Systems

 

Foto SE2 Sensor Shearografie Scherografie by isis-sys

 

She­aro­gra­phy and elec­tro­nic speck­le pat­ter inter­fe­ro­me­try (ESPI) are laser based, opti­cal mea­su­re­ment methods, working full field and non con­ta­ct. The She­aro­gra­phy sys­tems are app­lied for non dest­ruc­ti­ve tes­ting, but also for vibra­ti­on, defor­ma­ti­on and strain mea­su­re­ment. The reso­lu­ti­on of the dif­fe­ren­ti­al defor­ma­ti­on is a frac­tion of the wave length only und thus in the nano­me­ter ran­ge and below. The laser wave length is the refe­rence sca­le, so the reso­lu­ti­on is inde­pen­dent of the field of view. The field of view is in the ran­ge of mm² to m². The pre­pa­ra­ti­on of the object in only requi­red for sur­faces, which are opti­cal­ly non cooperative.

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The image shows a typi­cal she­aro­gra­phic mea­surment result for non dest­ruc­ti­ve tes­ting. The object is a honey­comb panel with dif­fe­rent pre­pa­red defects, which beco­me visi­ble even app­ly­ing small ther­mal load via light radiation.

Application: Non Destructive Testing

The main field of app­li­ca­ti­on of the She­aro­gra­phy sys­tems of isi-sys is non dest­ruc­ti­ve tes­ting (NDT). The full field dif­fe­ren­ti­al defor­ma­ti­on mea­su­re­ment of she­aro­gra­phy enab­les to loca­te espe­cial­ly struc­tu­ral­ly and mecha­ni­cal­ly rele­vant defects such as delamination’s, cracks or void due to local inho­mo­ge­ne­ous defor­ma­ti­on and strain dis­tri­bu­ti­on, when an exter­nal load is app­lied. In the prac­ti­cal app­li­ca­ti­on, this can be a ther­mal load via light sources or hot air guns, dyna­mi­cal load via Pie­zos­ha­kers or mecha­ni­cal loading steps such as chan­ge of the inter­nal pres­su­re of tubes and tanks or vacu­um loading by vacu­um cham­bers or vacu­um hoods.

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DIC (Digital Image Correlation)

 

Foto Kamera GT6600 Digitale Bildkorrelation by isi-sysDigi­tal image cor­re­la­ti­on is app­lied in solid mecha­nics, mate­ri­al rese­arch and deve­lo­p­ment of mecha­ni­cal­ly loa­ded mate­ri­als, com­pon­ents and struc­tures. DIC con­tri­bu­tes here espe­cial­ly due to the non con­ta­ct and full field mea­su­re­ment of defor­ma­ti­on and dis­pla­ce­ments and the deri­ved quan­ti­ties such as strain, vibra­ti­on, moti­on and velo­ci­ties for ana­ly­sis of the mecha­ni­cal pro­per­ties. The results are use for vali­da­ti­on of simulations.

The mea­su­re­ment results ori­gi­na­te from the sur­face of the object its­elf usual­ly by ste­reo came­ra sys­tems and eva­lua­ted with VIC 2D/VIC 3D soft­ware, but also wit­hin the solid by com­pu­ter tomo­gra­phy sys­tems (CT´s) and VIC Volu­me. isi-sys is sys­tem inte­gra­tor for VIC soft­ware in Euro­pe and clo­se deve­lo­p­ment part­ner of Cor­re­la­ted Solu­ti­ons, USA.

The reso­lu­ti­on of the defor­ma­ti­on and strain as well as its spa­ti­al and time reso­lu­ti­on is depen­ding on the sys­tem con­fi­gu­ra­ti­on. DIC sys­tem of isi-sys reach nano­me­ter sen­si­ti­vi­ty as well as time reso­lu­ti­on in nano­se­cond ran­ge. They have been app­lied on field of view below one mm² und abo­ve 100m², such as on rota­ting wind tur­bi­ne bla­de with a dia­me­ter of 114m.

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Application range of DIC for Strain and Deformation Measurement

DIC is app­lied for sta­tic and dyna­mic three dimen­sio­nal strain and defor­ma­ti­on mea­su­re­ment in the ran­ge of from 0,001% up to 1000% and abo­ve as well as for fati­gue tes­ting and moni­to­ring. Using high reso­lu­ti­on came­ras with line­ar and low noi­se sen­sor pro­per­ties a high spa­ti­al reso­lu­ti­on can be achie­ved, too. Time reso­lu­ti­on is actual­ly pos­si­ble up to 5 mil­li­on frames per second.

DIC enab­les a mea­su­re­ment, which have not been pos­si­ble with con­ven­tio­nal methods such as at high tem­pe­ra­tures, at high strains or on small field of view with high spa­ti­al reso­lu­ti­on. In a num­ber of cases DIC has repla­ced con­ven­tio­nal methods such as strain gau­ges or exten­so­me­ters – espe­cial­ly in the area of deve­lo­p­ment and rese­arch due to the full field and non con­ta­ct working principle.

Due to its advan­ta­ges and due to the impro­ved came­ras and incre­a­sing com­pu­ta­ti­on power the digi­tal image cor­re­la­ti­on sys­tems have dri­ven con­ven­tio­nal opti­cal methods for strain and defor­ma­ti­on such as pho­to­elasti­ci­ty and elec­tro­nic speck­le pat­tern inter­fe­ro­me­try out of the mar­ket to a wide extend.

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Video Stroboscope

 

Foto High Speed Videostroboskop by isi-sys

Used for simp­le visua­liz­a­ti­on, moni­to­ring and record­ing of vibra­ti­ons and rota­ti­ons in slow-moti­on. For quan­ti­ta­ti­ve eva­lua­ti­on in sub­pi­xel ran­ge, it can be exten­ded with image cor­re­la­ti­on (see above).

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Application: Vibration Analysis of operation deflection mode shapes

in full field 3D is pos­si­ble using high speed record­ing and app­ly­ing the pha­se sepa­ra­ti­on method (FFT-modu­le exten­si­on of VIC Soft­ware). The app­li­ca­ti­on of the pha­se reso­nance methods in com­bi­na­ti­on with e. g. elek­tro­dy­na­mic shakers or pie­zos­ha­kers is pos­si­ble using high reso­lu­ti­on slow speed sys­tems in com­bi­na­ti­on with a pha­se syn­chro­nis­ed came­ra trig­ge­ring using the Video­stro­bo­scope princip­le as descri­bed above.

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Piezoshaker Systems

 

Photo Piezoshaker PS X 03 by isi-sys

 

 

Desi­gned for vibra­ti­on exci­ta­ti­on in the k‑Hz ran­ge espe­cial­ly for non dest­ruc­ti­ve tes­ting. Sys­tems inclu­de spe­cial light weight high power pie­zo ampli­fiers for mobi­le app­li­ca­ti­on in NDT with she­aro­gra­phy and thermography.

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 Application: Vibration Monitoring

On shaker, test ben­ches, at non-acces­si­ble loca­ti­ons (endo­scope-use) and on lar­ge or micro objects.

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