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.


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.


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.”

Vibration Analysis of a Brake Disc

Bremsen1 Bremsen2
Auto­mo­bi­les are sub­ject to many forces using ope­ra­ti­on. Vibra­ti­ons from the engi­ne or the road-sur­face trans­mit through the vehicle’s chas­sis and sus­pen­si­on to the most essen­ti­al mecha­ni­cal com­po­nent of the vehic­le, the bra­ke system.


In this exam­p­le, a 14” dia­me­ter bra­ke disc from a hea­vy­du­ty truck was exci­ted using a small ham­mer to mea­su­re the vibra­ti­on shapes of the rotor. The three-dimen­sio­nal ope­ra­tio­nal deflec­tion shapes were easi­ly iden­ti­fied and mea­su­red using the Vic-3D™ HS Vibra­ti­on Ana­ly­sis Sys­tem. Ampli­tu­des as small as 40 nano­me­ters were mea­su­red at a fre­quen­cy of appro­xi­m­ate­ly 2,000 Hz.


Strain Measurement on a Gearwheel


Assem­bled com­pon­ents typi­cal­ly have com­plex inter­ac­tions with one ano­ther. Cont­act points can vary during ope­ra­tio­nal cycles due to part move­ment. This means that the loca­ti­ons of peak strains can be hard to pre­dict, and they are often not sta­tio­na­ry. The move­ment of parts can also make it imprac­ti­cal to main­tain elec­tri­cal con­nec­tions with gau­ges. Even when they are sta­tio­na­ry and easy to loca­te, the hig­hest strains can be con­cen­tra­ted in very small are­as or have high gra­di­ents. Peak values may be lost to the aver­aging effect pro­du­ced by gauges.



Vic-3D pro­vi­ded a means for making strain mea­su­re­ments across the enti­re pro­fi­le of the gear tooth. Becau­se it pro­vi­des full-field mea­su­re­ments, it was not neces­sa­ry to choo­se a par­ti­cu­lar point at which mea­su­re­ments would be made. This allo­wed the peak strains to be cle­ar­ly visua­li­zed and accu­ra­te­ly mea­su­red at various stages of the ope­ra­tio­nal cycle. Vic-3D also mea­su­red dis­pla­ce­ment in three dimen­si­ons. This fea­ture allo­wed our cus­to­mer to reco­gni­ze and quan­ti­fy twis­ting of the gear tooth under load.

Exhaust pipe

Exhaust1The engi­neers at Cumm­ins design and test their engi­nes to with­stand real-world con­di­ti­ons, ran­ging from mili­ta­ry deploy­ments to hea­vy-duty indus­tri­al sites. Cumm­ins engi­neers want to know exact­ly how their parts are deforming under the com­bi­na­ti­on of ther­mal and mecha­ni­cal loads. This means they’ve got to per­form their tests with the engi­nes run­ning – and hot.

Becau­se of the com­plex strain fields pro­du­ced under the­se con­di­ti­ons, con­ven­tio­nal gau­ges can­not satis­fy Cumm­ins’ requi­re­ments. FEA simu­la­ti­ons are also limi­t­ed, due to the uncer­tain boun­da­ry con­di­ti­ons. With the Vic-3D sys­tem, Cumm­ins engi­neers are able to obtain detail­ed three-dimen­sio­nal strain mea­su­re­ments. The­se mea­su­re­ments are made under real loa­ding con­di­ti­ons while the engi­ne is run­ning. In addi­ti­on, the Vic-3D sys­tem is easy to set up and can mea­su­re both small parts and lar­ge assemblies.




Paul Gloeck­ner, seni­or rese­arch engi­neer at Cumm­ins, explains the useful­ness of the Vic-3D sys­tem as fol­lows: “This tool allows us to make mea­su­re­ments that were pre­vious­ly not pos­si­ble. It has also allo­wed us to con­sider­a­b­ly redu­ce the time requi­red for the­se tests.”

Microscopic Strain Measurement

Combination of a special stereomicroscope with Vic-3D digital image correlation on electronic components.


Uni Wien Mikroskop

Mea­su­re­ment set up: Ste­reo micro­scope mounted

on x‑y-z-micro­ta­ble (backside) and ten­si­le machi­ne (right).


Uni Wien Mikroskop2

Uni Wien Mikroskop3

Ser­ver­ed cera­mic capa­ci­tor chip under ben­ding load (image width approx. 4mm):
Strain in x‑direction (upper image) and y- direc­tion (lower image).


Uni Wien Mikroskop4

Uni Wien Mikroskop5

Stan­dard deri­va­ti­on (upper) under load : An increased value occurs on the midd­le against the reference
sta­te by the local­ly small bul­ge at the cont­act bet­ween chip and board (see 3D con­ture below). This might be caused
by mate­ri­al , which is pres­sed tog­e­ther bet­ween the two parts (inclu­ding the colour lay­er). In the upper area the
increased values of the stan­dard deri­va­ti­on is cau­sed by the redu­ced speck­le density.