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.

Strain Measurement on a Gearwheel

Challenges

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.

 

Solution

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.

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.

 

Vic-3D High-Speed Vibration Analysis System

Vibration1               Vibration2

 

The Vic-3D™ Vibra­ti­on Ana­ly­sis Sys­tem by Cor­re­la­ted Solu­ti­ons, Inc. is a new addi­ti­on to the Vic-3D pro­duct line of mea­su­re­ment solu­ti­ons. Vic-3D Vibra­ti­on enab­les full-field 3D viewing, mea­su­re­ment, and ana­ly­sis of tran­si­ent events. Full-field ope­ra­tio­nal deflec­tion shapes in the fre­quen­cy domain can easi­ly be seen and com­pa­red with levels of accu­ra­cy in the nano­me­ter range.

The image abo­ve on the left is a moun­ted model jet pla­ne which has under­go­ne a tran­si­ent vibra­ti­on event.  To the right, the 3D vibra­ti­on data obtai­ned from the event is shown as a 2D con­tour over­lay on this image.  The data over­lay enab­les the user to see exact­ly how much defor­ma­ti­on is occur­ring and whe­re it is occur­ring.  This infor­ma­ti­on is avail­ab­le at each fre­quen­cy whe­re deflec­tion shapes occur.

The data below dis­plays one ope­ra­tio­nal deflec­tion shape obtai­ned with the VIC-3D Vibra­ti­on Ana­ly­sis Sys­tem. Three-dimen­sio­nal dis­pla­ce­ments, strains, velo­ci­ties, and acce­le­ra­ti­ons can all be com­pu­ted in the ana­ly­sis soft­ware.  The result is not only visu­al, but also enab­les the user to export quan­ti­ta­ti­ve data (ASCII, Mat­Lab, CSV, etc.) from the sample’s beha­vi­or for FEA ana­ly­sis and vali­da­ti­on.  A 3D ani­ma­ti­on of the model jet’s ope­ra­tio­nal deflec­tion shape at 441 Hz is shown below, with only 12 microns of dis­pla­ce­ment amplitude.

 

Film Vibration3D_W_431Hz

 

What is transient vibration analysis? 

Tran­si­ent vibra­ti­on ana­ly­sis is the pro­cess of moni­to­ring, mea­su­ring, and ana­ly­zing the con­di­ti­on of sam­ples during a tran­si­ent event. Mate­ri­al pro­per­ties can also be obser­ved through the ana­ly­sis of ope­ra­tio­nal deflec­tion shapes and mode shapes crea­ted by the event. The­se full-field 3D shapes can pro­vi­de use­ful infor­ma­ti­on which can be used to impro­ve and cor­rect a sample’s balan­ce, dis­pla­ce­ment, fle­xu­re, rigi­di­ty, and over­all pro­duct per­for­mance.  Mea­su­ring ope­ra­tio­nal deflec­tion shapes can help ans­wer the ques­ti­on: “How much is this struc­tu­re actual­ly moving at a par­ti­cu­lar frequency?”

 

Why is it important to you?

Ope­ra­tio­nal deflec­tion shapes crea­ted from tran­si­ent tests show how a sam­ple can have a non­uni­form thic­knes­ses, sur­face irre­gu­la­ri­ties, weak points, cracks and/or other imper­fec­tions & flaws.  This infor­ma­ti­on can be use­ful at any point in the pro­cess of achie­ving your over­all goal, from wri­ting a pro­ject pro­po­sal to tes­ting a func­tio­n­al or fai­ling part in the field: The Vic-3D Vibra­ti­on Ana­ly­sis Sys­tem

  • Has a jus­ti­fia­ble pri­ce point when wri­ting proposals
  • Can be used: 
    • To crea­te and vali­da­te FE models when designing parts & equipment
    • During the rese­arch and design process
    • In the pro­duct tes­ting phase
    • To pro­vi­de manu­fac­tu­ring qua­li­ty assurance
    • To cer­ti­fy and assu­re equip­ment is ope­ra­ting as expec­ted and required
    • To mea­su­re and ana­ly­ze parts post-installation
    • To ensu­re pro­duct qua­li­ty and per­for­mance over time and in the field
    • When reas­ses­sing pro­duct func­tio­n­a­li­ty over time

 

Examp­les of tran­si­ent events which can be mea­su­red are the following:

▪ Door Slams ▪ Modal Ham­mer Strikes
▪ Engi­ne Start-ups ▪ Drop Tests
▪ Explo­si­ve Testing ▪ Bal­listic Testing

 

System Features 

  • View, com­pa­re, ani­ma­te, graph, extract, and export data for easy FEA comparison
  • Mea­su­re 3D full-field, high fre­quen­cy mode shapes with nano­me­ter resolution
  • Mea­su­re extre­me­ly low ampli­tu­des with extre­me­ly high accelerations
  • Full-field strain, defor­ma­ti­on, and shape varia­bles are still available
  • Easy pro­ce­du­res, accu­ra­te results
  • User friend­ly interface
  • Only a frac­tion of the pri­ce of a laser vibro­me­ter system

 

Advantages over other measurement techniques

While tra­di­tio­nal vibra­ti­on mea­su­re­ment tech­ni­ques can be use­ful, they also have many draw­backs.  For examp­le, acce­le­ro­me­ters can beco­me unglued during tes­ting, can mass-load a sam­ple, and can only pro­vi­de point to point mea­su­re­ments, often only in a sin­gle pla­ne. Pre-tes­ting and tes­ting can also take days or even weeks to per­form on lar­ge struc­tures.  With the Vic-3D Vibra­ti­on Ana­ly­sis sys­tem, the­re are no adhe­si­ves, wires, signal ana­ly­zers, power ampli­fiers, or load cells necessa­ry for detail­ed vibra­ti­on results.  Obtai­ning thousands of data points for a tiny, com­plex struc­tu­re or a lar­ge one is as easy as chan­ging a pair of len­ses. Simi­lar to digi­tal image cor­re­la­ti­on, laser vibro­me­ters can pro­vi­de a non-con­ta­ct mea­su­re­ment solu­ti­on, but simi­lar to acce­le­ro­me­ters, they are also only able pro­vi­de point to point mea­su­re­ments.  A 3D mea­su­re­ment can be achie­ved with mul­ti­ple scan­ning vibro­me­ters, but the­se are usual­ly moun­ted on lar­ge robot arms which can take up valu­able labo­ra­to­ry space and can­not be moved easi­ly once instal­led.  Addi­tio­nal­ly, the­se sys­tems are unre­a­son­ab­ly expen­si­ve for many app­li­ca­ti­ons.  The Vic-3D Vibra­ti­on Ana­ly­sis sys­tem can be taken into the field with any com­pa­ti­ble lap­top and tog­e­ther with the Vic-3D Work­sta­tion, the sys­tem can beco­me mobi­le and secu­re insi­de your faci­li­ty.  Vic-3D Vibra­ti­on Ana­ly­sis is only a frac­tion of the pri­ce of a 3D scan­ning laser vibro­me­ter sys­tem, and sin­ce the modu­le can be added onto any exis­ting 3D sys­tem, it’s even more affordable.