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Non Destructive Testing

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.

 

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
 

Vakuum loading on battery packs

Air inclu­sion or air pock­ets in mod­ern Li-bat­tery packs is a seri­ous and dan­ger­ous prob­lem. The isi-sys SE2 sen­sor is able to detect tiny and large defects such as air bub­bles, air pock­ets, cracks and oth­er with­in a sec­ond. The defects can be far below or near to the sur­face. An exam­ple of a bat­tery pack (test sam­ple from Uni­ver­si­ty of Munich, IWB) and the mea­sure­ment result is shown below.

Test set­up:

The test has been done by SE2 sen­sor in com­bi­na­tion with a glass vac­u­um cham­ber for a sim­ple man­u­al test. This is an eco­nom­ic solu­tion for spot NDT by man­u­al ser­vice. For auto­mat­ed series test in pro­duc­tion dif­fer­ent setups are required.

Test poce­dure:

The bat­tery packs are test­ed by small pres­sure dif­fer­ences of some mbar, which can be applied in sec­onds or below in small cham­bers. The sen­sor is mon­i­tor­ing the sur­face of the bat­tery pack while the pres­sure is changed, mea­sur­ing the dif­fer­en­tial defor­ma­tion of the sur­face. Due to the expan­sion of the air bub­bles and air pock­ets, the air inclu­sions can be locat­ed such as shown in the fol­low­ing images.

The first image shows the live view of the bat­tery pack from the sen­sor. The sec­ond shows the recon­truct­ed phase, which is cor­re­spond­ing to the local defor­ma­tion gradient.

battery pack3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

battery pack2

Gen­er­al­ly the required pres­sure dif­fer­ence depends on the defect depth, defect size an the mechan­i­cal stiff­ness of the test­ed struc­ture, but in gen­er­al the load is small due to the high sen­si­tiv­i­ty of the sen­sor detect­ing dif­fer­en­tial defor­ma­tions of the surface.

Dynamic excitation on a spacecraft

Historic measurement from 2000

This exam­ple com­bines the Vibro­grafie Sys­tem with a Piezoshak­er Mod­ule for a non-destruc­tive inspec­tion. The heat shield with C‑Si‑C (car­bon fiber-sil­i­con com­pos­ite) of the prospec­tive recov­ery vehicle/ space­craft x38 was reviewed by Shearog­ra­phy.

Spacecraft6

For eas­i­er han­dling, the Piezoshak­er mod­ule is com­pressed on the sur­face of the object via a suc­tion base.
(a) Piezoshak­er mod­ule, (b) the heat shield of the space­craft X38 © Flight of the space­craft X38.

x

spacecraft2

The pic­ture shows the deter­mi­na­tion of times of the heat shield with the nat­ur­al fre­quen­cy (1400 Hz).

 x

spacecraft3

Local vibra­tion forms of defects at 10kHz and 18 kHz of the nose hood in the marked area of the image. Dur­ing the inspec­tions, two defects have been detect­ed in the upper area of the dog.

NDT on Wind Rotor Blades

First test NDT Mea­sure­ment by shearog­ra­phy on a wind tur­bine blade in 1996 by P. Mäck­el, L. Yang, G. Kupfer and A. Tiemich at Kas­sel Uni­ver­si­ty. The object is a spe­cial wind rotor blade of a sin­gle wing wind tur­bine ener­gy plant.

RotorBlade

Applied load­ing method: Load­ing by inter­nal pres­sure (the blade has been sealed). A man­u­al pump has been used to increase a pres­sure dif­fer­ence against the sur­round­ing. The fringe images show areas at dif­fer­ent loca­tions. The fringes are pro­por­tion­al to the out of plane defor­ma­tion gra­di­ents of the sur­face, which allows to iden­ti­fy inho­mo­ge­neous stiff­ness of the struc­ture: left — Delam­i­na­tion; right — Axi­al crack; cen­ter ‑Struc­tur­al change over (dif­fer­ent num­ber of glas­fiber layers).

 

 

Dynamic loading on a yacht mast

The exam­ple shows an appli­ca­tion of NDT on a 30m CFK yacht mast (low­er left). The time aver­age result of the SE1 mea­sure­ment and dynam­ic load­ing by our Piezoshak­er (low­er right) is indi­cat­ing a larg­er delim­i­ta­tion below the sur­face start­ing from a small vis­i­ble crack. Usu­al­ly, small cracks are often seen on the sur­face, but not all are relat­ed to delam­i­na­tion, which needs any repair.

NDT Yacht   NDT Yacht2


SE1 with Piezoshak­er for dynam­ic loading


Defect detect­ed by Vibrog­ra­phy / dynam­ic loading


Dynamic loading on rudder blade

 

NDTRuder

Detec­tion and mea­sure­ment of defects on a rud­der blade by the SE-Sen­sor and dynam­ic load­ing.

NDTRuder2

Set­up for mea­sure­ment on a rud­der by dynam­ic loading.

The direct rigid mount­ing of the sen­sor on the rud­der by the suc­tion cups allows out­door mea­sure­ment even at strong winds with high flex­i­bil­i­ty. The high qual­i­ty inter­fer­ence fil­ters of the sen­sor per­mits mea­sure­ment under day light conditions.

 

NDTRuder3   NDTRuder5  NDTRuder4

A: 9,3 kHz                                            B: 7,5 kHz                                           C: 5,5 kHz

Mea­sure­ment results (time aver­age) show­ing local vibra­tion modes of defects due to reduced or inho­mo­ge­neous stiff­ness of the mate­r­i­al. Even if a big field of view is select­ed, it is pos­si­ble to detect small defects. Defect size and type as well as the depth of the defect (delam­i­na­tion) deter­mine the nor­mal modes (res­o­nance fre­quen­cy) of the local defect area.