Spatial resolution and accuracy

VIC-3D Pro­fes­sion­al Sys­tems deliv­er full­field, high­ly accu­rate shape, motion and defor­ma­tion mea­sure­ments. Lim­its can be traced for indi­vid­ual setups by sim­ple pro­ce­dures out­lined in the VDI-2626 direc­tive espe­cial­ly devel­oped for dig­i­tal image cor­re­la­tion (DIC). This exam­ple shows prin­ci­pal strain ε1 and ε2 (click to start video). In cas­es with local high peaks, a high spa­tial res­o­lu­tion can be the key to achiev­ing pre­ci­sion and accu­ra­cy for peak strain, in addi­tion to excel­lent SNR and cal­i­bra­tion of VIC. Video gen­er­at­ed with­in VIC iris work­space by isi-sys.


A high opti­cal res­o­lu­tion com­bined with suit­able speck­le size and den­si­ty is not only required to resolves the spa­tial strain dis­tri­b­u­tion as in the case before, but also improves accu­ra­cy in par­tic­u­lar for strain peak deter­mi­na­tion (upper right sketch), due to the fact that sub­set and strain fil­ter sizes (in pix­el scale) are fur­ther reduced (in absolute scale) com­pared to the peak strain dis­tri­b­u­tion. This fact also mat­ters for strain gauge size, as they are also not point strain mea­sure­ment device but inte­grat­ing over their length. The low­er right image is zoomed down to the pix­el  size range in VIC. It shows a high end case using the Blue-Fal­con. The lit­tle grey val­ue squares (two marked green) cor­re­sponds to the inten­si­ty val­ue of a pix­el and cov­er an area of 1.83 μm2. The vis­i­ble speck­le diam­e­ters are in the range between 3 to 8 pix­el. The red and yel­low squares also indi­cate the pix­el size oper­at­ing with larg­er FOV (mag­ni­fi­ca­tion 1:7 and 1:14), which would even not resolve speckles.



Bending Test

The video exam­ple shows a four point bend­ing test set­up for a met­al beam with drilled holes (side view). The beam sur­face is mea­sured by a VIC-3D Pro­fes­sion­al stereo sys­tem from below via a sur­face coat­ed mir­ror. The mea­sured prin­ci­pal strain are pro­ject­ed on the mir­rored image of the sam­ple sur­face. Mea­sure­ment of 9/2023, Uni­ver­si­ty of Lübeck.

Automated NDT system for filament wound tubes

This sys­tem is used for auto­mat­ed, non-destruc­tive test­ing of fil­a­ment wound pipes. The pipes are rotat­ed in 90° steps around their axis to mon­i­tor four cir­cum­fer­en­tial seg­ments. Two SE4 sen­sors with 2 x 4000 px are applied per seg­ment along the tube axis. For a tube length of 1m @ 8000 px, this leads to 0.125 mm/px spa­tial pix­el res­o­lu­tion for all 8 image seg­ments. After insert­ing the pipes the ends are auto­mat­i­cal­ly sealed and inter­nal pres­sure is used as the load­ing method. Since this cor­re­sponds to the usu­al oper­at­ing load of the tubes, the mea­sured defor­ma­tion dis­tri­b­u­tion visu­al­izes main­ly the rel­e­vant struc­tur­al defects in con­trast to oth­er load­ing meth­ods such as ther­mal load­ing.

Due to the high defor­ma­tion sen­si­tiv­i­ty of the SE4 sen­sors com­bined with the high spa­tial pix­el res­o­lu­tion even the small­est defects can be detect­ed. An oper­a­tor final­ly cat­e­go­rizes the object as IO / NIO. Auto­mat­ed or AI-based image analy­sis is pos­si­ble, but it depends on the appli­ca­tion and detec­tion require­ments. At the end of the mea­sure­ment, a report is gen­er­at­ed and auto­mat­i­cal­ly stored as a PDF in a direc­to­ry spec­i­fied by the user.

The tubes are insert­ed and removed man­u­al­ly. An exten­sion with col­lab­o­ra­tive robots or inte­gra­tion into pro­duc­tion lines is pos­si­ble. Sev­er­al thou­sand tubes have already been test­ed per year with­out prob­lems and maintenance.

Automated NDT on a guide vanes ring of a jet engine

Here the SE4 Sen­sor is used in com­bi­na­tion with an auto­mat­ic attached Piezoshak­er for dynam­ic exci­ta­tion. The SE4 is oper­at­ed in time aver­age mode dur­ing fre­quen­cy sweep­ing for detect­ing local defect res­o­nances of the sol­der­ing of the seal­ing band. The two mea­sure­ments on the left show pre­pared defects. Upper left: hor­i­zon­tal shear­ing, time aver­age mode; Below: ver­ti­cal shear­ing and stro­bo­scop­ic mode for phase reconstruction.


Application for Optimization of Laser Beam Welding by Ultrasonic Wave Superposition

The poten­tial of ultra­son­ic wave super­po­si­tion to improve the prop­er­ties of laser beam weld­ing was inves­ti­gat­ed using sta­tion­ary and mov­ing Piezoshak­er-Sys­tem at the Depart­ment of Cut­ting and Join­ing Man­u­fac­tur­ing Process­es (tff) at the Uni­ver­si­ty of Kas­sel. An exam­ple of this is the test on the high-strength steel alloy 22MnB5, which is pre­sent­ed here. Adap­ta­tion to oth­er weld­ing process­es and mate­ri­als is possible. 

The influ­ences of the var­i­ous exci­ta­tion para­me­ters of the Piezoshak­er on the ultra­son­ic wave super­po­si­tion were inves­ti­gat­ed, e.g. the dis­tri­b­u­tion of the AlSi-coat­ing par­ti­cles with­in the join­ing zone as well as the weld seam prop­er­ties [1].

The isi-sys Piezoshak­er-Sys­tem was used for the mov­ing wave super­po­si­tion, as shown in Fig. 1 The sys­tem con­tains a 2‑channel Piezoam­pli­fier of the HPDA‑0–180-2C series and two Piezoshak­ers of the PS-W-02 series. The Piezoshak­ers are firm­ly con­nect­ed to the laser optics via a mount and are moved rel­a­tive to the com­po­nent sur­face at a defined dis­tance from the laser beam. These are pressed onto the com­po­nent sur­face with a defined force using pneu­mat­ic cylin­ders. Uneven­ness and dif­fer­ences in the thick­ness of the join­ing part­ners can be compensated.
















Fig. 1 (left): The dis­tri­b­u­tion of the AlSi-coat­ing in com­par­i­son with­out (a) and © and with (b) and (e) influ­ence of an ultra­son­ic wave super­po­si­tion by isi-sys Piezoshak­er dur­ing laser beam weld­ing with false-col­or images of EDS-analy­sis (d) and (f) [1]

Fig. 2 (right): Super­im­posed SEM-images and sec­tioned inverse pole fig­ure map­pings (IPFM) of a weld seam with­out (a) and with ultra­son­ic super­po­si­tion (b) mea­sured with elec­tron backscat­ter dif­frac­tion shown as inverse pole fig­ure in Z‑direction [1]

[1] Pub­lished in: C. Wolf, S. Völk­ers, I. Kryukov, M. Graß, N. Som­mer, S. Böhm, M. Wun­der, N. Köh­ler und P. Mäck­el, „Enhance­ment of Weld­abil­i­ty at Laser Beam Weld­ing of 22MnB5 by an Entrained Ultra­son­ic Wave Super­po­si­tion,“ In: Mate­ri­als 2022, Bd. 15, 4800.

Strain Gauge Comparison

In this exam­ple a Vic-3D mea­sure­ment with 5MP CMOS Cam­era was per­formed. The acryl spec­i­men is fixed in a ten­sile test­ing machine. A strain gauge is attached at the back in com­bi­na­tion with a SCAD 500 strain gauge ampli­fi­er. The out­put of the SCAD 500 was con­nect­ed to the DAQ of the DIC sys­tem. The strain results are record­ed par­al­lel with the Vic-3D mea­sure­ment and plot­ted in a dia­gram. The cam­era type is equipped with Sony 5Mpx Pregius sen­sor, 75 fps.

Strain Gauge Comparison-1  Strain Gauge Comparison-1a

Image 1: Vic-3D mea­sure­ment of the acryl specimen


Strain Gauge Comparison-2









Image 2: Com­par­i­son of strain gauge data (red curve) and DIC Strain data (black curve)


The Vic-3D data match near­ly per­fect with the strain gauge data. Even at low strains the dif­fer­ence is less than 25 micro strain.

NDT of Carbon-NOMEX (honeycomb core) composite: Dynamic loading on a large yacht hull

Marine NDE (Spain) used the tech­ni­cal advan­tages of our Shearog­ra­phy-Sys­tem espe­cial­ly in com­bi­na­tion with the dynam­ic exci­ta­tion for non-destruc­tive exam­i­na­tion (NDE) of large areas such as com­plete yacht hulls (see image below). The hull with a lenghts of 30,5m was a car­bon-fir­ber-com­pos­ite and part of high per­for­mance sail­ing yacht in build. Because of the full-field method (100% of the inspect­ed area is exam­ined), the test­ing of the entire hull required only 240 shots, in three workdays.


The yacht hull con­sists of a sand­wich con­struc­tion, where are in par­tic­u­lar used hon­ey­comb cores (NOMEX).

Marine NDT1Marine NDT2







On the left — A shearo­gram of a detect­ed bond­ing defect (in red oval). The yel­low X marks the loca­tion of the core sam­ple shown at the right. The destruc­tive test con­firms the shearo­gram’s indi­ca­tion that there is a sig­nif­i­cant nev­er-bond between the hon­ey­comb core mate­r­i­al and the film adhe­sive in this area.


Dynamic loading on a wind turbine blade and resin bridges

Analysis of a wind turbine blade

The test pan­el was an orig­i­nal sec­tion of a wind tur­bine blade with a defect (a foam block with bridges). Pre­vi­ous­ly the defect was locat­ed by infil­tra­tion of col­or through small drilled holes. The sam­ple is exam­ined non-destruc­tive­ly by the SE-Sen­sor.


Section RotorBlade-a  Section RotorBlade2

left: Set-up

right: Time aver­age result at fre­quen­cy of 2569Hz show­ing the debond­ing area.





Section RotorBlade3Section RotorBlade4left: Live view of sur­face includ­ing shearing.

right: Time aver­age mea­sure­ment from the marked area in the live image.




De-bonding of resin bridges

A GFRP sand­wich with foam blocks and resin bridges should be exam­ined. The detec­tion of the defect type und struc­ture is very quick and reli­able in this case, because the defects are vis­i­ble, not only at their local nat­ur­al fre­quen­cies, but also due to their forced deflec­tion shapes over a wide fre­quen­cy bandwidth.

Section2 RotorBlade


The exci­ta­tion fre­quen­cies of the select­ed mea­sure­ments are 1398 Hz (1), 3133 Hz (2), 2442 Hz (3) and 4906 Hz (4) — num­ber­ing in fol­low­ing images:

Section2 RotorBlade2