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
 

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.

Operation mode analysis on a mobile phone during vibration alert

Nokia3

x

Refe­rence coor­di­na­tes and con­tour of the mobi­le phone.

 

 

 

x

 

This arti­cle descri­bes the mea­su­re­ment and ana­ly­sis of the ope­ra­ti­on deflec­tion shapes and rigid body vibra­ti­on moti­ons of a mobi­le pho­ne exci­ted by its vibra­ti­on alert. The mear­ure­ment is done, using a non con­ta­ct, 3D, full-field, high speed ste­reo image cor­re­la­ti­on sys­tem in com­bi­na­ti­on with the new Vic-3D FFT modu­le ana­ly­zes the recor­ded defor­ma­ti­on data in the fre­quen­cy domain by pha­se-sepa­ra­ti­on method.

Nokia

The mea­su­red defor­ma­ti­ons and dis­pla­ce­ments during the vibra­ti­on alert are eva­lua­ted against the refe­rence sta­te for each ste­reo image pair. In this case the record­ing time covers about 5,5 seconds with 1000 FPS cor­re­spon­ding to about 5500 sin­gle measurements.

The fol­lowing figu­re show the average vibra­ti­on ampli­tu­de U.

 

Nokia2

Dynamic Compression of Metals

Dynamic compression

Stu­dy­ing the beha­vi­or of metals during a high-speed dyna­mic com­pres­si­on event has always been chal­len­ging due to the com­plex test set up and fast data cap­tu­re rates requi­red. Cur­r­ent­ly, very litt­le lite­ra­tu­re is avail­ab­le regar­ding defor­ma­ti­on beha­vi­or at strain rates of  10 to 500s-1. Uti­li­zing high-speed came­ras, the Vic-3D HS sys­tem can be used to quan­ti­fy the sur­face dis­pla­ce­ments and strains in three dimen­si­ons over the ent­i­re field with gre­at pre­cisi­on. Digi­tal Image Cor­re­la­ti­on (DIC) has gai­ned widespread popu­la­ri­ty over recent years in such high-speed app­li­ca­ti­ons due to its high accu­ra­cy, fle­xi­bi­li­ty and ease of use.

 

 

 

Dynamic compression2In this examp­le, a 6mm dia­me­ter cylind­ri­cal spe­ci­men was com­pres­sed at a strain rate of 50s-1. The Vic-3D HS sys­tem was used to cap­tu­re the  sur­face dis­pla­ce­ments and  strains on  the  spe­ci­men during the event. A ran­dom speck­le pat­tern is app­lied to the spe­ci­men that allows the ana­ly­sis soft­ware to easi­ly track the defor­ma­ti­on to sub-pixel accu­ra­cy. Alt­hough the high- speed came­ras are capa­ble of much hig­her cap­tu­re rates, for this test they were set to an appro­pria­te frame rate of 14,400fps to maxi­mi­ze spa­ti­al reso­lu­ti­on while acqui­ring an ade­qua­te num­ber of images during the event. The came­ras were post-trig­ger at a reso­lu­ti­on of 1024 x 400 pixels. After the event, the images are trans­fer­red to the computer’s  hard  dri­ve, and  then  post-pro­ces­sed using Vic-3D ana­ly­sis software.

Images cour­te­sy of Amos Gilat & Jere­my Seidt at Ohio Sta­te University.

 

 

Contractions of a Muscle

Bio­me­cha­nic rese­ar­chers were stu­dy­ing the con­trac­tions of a rat Tibia­lis Ante­rior mus­cle.  It was desi­ra­ble to quick­ly and accu­rate­ly quan­ti­fy the over­all move­ments, as well as loca­li­zed variations.

Challenges

Becau­se the expe­ri­ments invol­ved live tis­su­es, con­ven­tio­nal gau­ges were dif­fi­cult to app­ly and ten­ded to inter­fe­re with the moti­on under stu­dy.  It was important to cap­tu­re data quick­ly, and for as many points as pos­si­ble.  Mar­ker tracking had been used, but pro­vi­ded only gross aver­a­ges.  It was also time-con­suming and tedious for the rese­ar­chers to pro­cess this type of  information.

Solution

The Vic-3D sys­tem was used to rapidly cap­tu­re con­trac­tion data over the ent­i­re mus­cle sur­face.  Due to the system’s speed and sim­pli­ci­ty, it was pos­si­ble to make nume­rous mea­su­re­ments at pre­cise­ly timed inter­vals.  The­re was no inter­ac­tion with the spe­ci­men, and no need to guess which are­as would be of grea­test interest.

The resul­ting mea­su­re­ments pro­vi­ded high spa­ti­al reso­lu­ti­on and made it pos­si­ble to iden­ti­fy nume­rous are­as whe­re “bun­ching” of the mus­cle tis­sue cau­sed signi­fi­cant varia­ti­ons in mus­cle con­trac­tion.  The­se are­as had not been pre­vious­ly iden­ti­fied with con­ven­tio­nal methods.  Final­ly, all cal­cu­la­ti­ons were done auto­ma­ti­cal­ly.  This saved con­si­derable time and avoided the pos­si­bi­li­ty of human error in the data processing.

 

Deformation Measurement

Aerospace Application Example

aerospace_1_notitle-300x247Air­bus has built a repu­ta­ti­on for inno­va­ti­ve air­craft, reco­gni­zed around  the world for their safe­ty and effi­ci­en­cy. All of the­se attri­bu­tes are dri­ven by a top-notch tes­ting pro­gram, who­se inno­va­ti­ve prac­ti­ce are evi­den­ced by their use of the Vic-3D mea­su­re­ment system.

One of the goals of the Air­bus tes­ting pro­gram is to cha­rac­te­ri­ze the struc­tu­ral dama­ge cau­sed by col­li­si­ons bet­ween the air­craft and small pro­jec­ti­les such as birds and other ground based debris, and to ensu­re that the struc­tu­ral inte­gri­ty of the air­craft is maintained.

This type of event can be repro­du­ced by firing a varie­ty of dif­fe­rent types of pro­jec­ti­le at a pie­ce of air­craft struc­tu­re at a high velo­ci­ty. The results obtai­ned can be used to com­pa­re with com­pu­ter models of the struc­tu­re under impact loads, lea­ding to more high­ly opti­mi­zed and safer designs.

 

aerospace_2_notitle-300x224Dr. Richard Bur­gue­te, expe­ri­men­tal mecha­nics spe­cia­list at Air­bus UK sin­ce 1997, exp­lains the bene­fits of this approach as fol­lows: “The VIC-3D sys­tem allows us to be sure we have cap­tu­red all of the rele­vant data, some of which might have other­wi­se been unobtainable.”