BR StrainMaster 2015-Prelim

8/10/2019 BR StrainMaster 2015-Prelim

1/12

LaVisionWe count on Photons

StrainMasterAdvanced Digital Image Correlation Systems

for Optical Full Field Measurement of

Material Strain, Displacement and Shape


2/12

2

StrainMaster from LaVision combines the most advancedDigital Image Correlation (DIC) algorithmswith the highest quality hardware to provide a complete device for materials analysis.StrainMaster isapplicable across all industries investigating material behaviour and gives fast, highly accurate results

via an easy to use PC based interface.

A range ofStrainMaster systems are available from portable eld work machines to highly specializedlab versions. Any system can be tailored to suit your particular requirements, and are appropriate forboth industrial and academic applications across a vast range of subject areas. Unlike many standardDigital Image Correlation (DIC) systems, LaVisionsStrainMaster is insensitive to the speckle pat-tern distribution and in many cases the natural surface of the material is quite sufcient to allow theacquisition of highly precise displacement and strain data.

4 tensile, compression, and bend testing4 material characterization4 ultra-fast impact and blast4 high temperature4 crack detection4 granular ows4 cyclic fatigue4 Fluid Structure Interaction (FSI)4 sub-surface defects

StrainMaster can be supplied as a complete turn-key system or as stand alone software for importingand processing images from an external source such as a Scanning Electron Microscope (SEM). Thesystem offers a complete solution and data management system able to drive hardware, acquire images,process data, validate and display or export information. LaVisions approach to Image Correlationmeans that all of the pertinent information is visible and the user chooses the level of post-processing.Whilst intelligent smoothing may be appropriate for standard materials undergoing tests in the elasticregime, this may not be appropriate in other cases where local discontinuities may be present but theironset cannot be predicted. The LaVision approach allows the user to inspect the raw displacementresults prior to deciding upon the type of ltering necessary.

4 complete camera integration including high speed devices4 controller with A/D converter for synchronized logging of load signal4 total control over post-processing - raw data is always available4 compact and robust mechanics4 complete control, analysis, and data management within one software package4 fast and accurate processing4 live gauge extensometer mode with scaled analogue output for strain control4 dedicated Add-on forMATLAB, and export formats including ABAQUS INP

Introduction

StrainMasterOptical Technology for

Full Field Strain Measurement

Applications

System Features


3/12

Digital Image Correlation (DIC) is a method to compute local displacements in a sequence of imagesshowing some kind of specimen deformation. The images are discretized into small subsets of NxNpixels, and the algorithm tracks the pattern within each subset. Where the pattern matching is maxi-

mized (or the differences minimized), this represents the local displacement. Repeating this acrossthe entire image for all subsets yields a full eld map of data, which is similar to having thousandsof virtual extensometers or strain gauges on the sample surface. Moreover, by using a stereoscopiccamera setup and corresponding calibration routines, DIC is also able to access out of plane displace-ments and changes in surface topology.

Within the StrainMaster DIC software a Least Squares Matching (LSM) approach with subset de-formation is used to match the pattern in combination with higher order spline interpolation of thegreyscale images.

Usually, the displacement eld is calculated relative to the specimen in its undeformed state (typicallythe rst image in the sequence). In cases where the deformation is relatively small the pattern inimage N is matched directly back to the reference image. However for large deformations the localpattern experiences signicant changes, and a sum of differential approach is used whereby the pat-tern is matched between successive images and then summed in a Lagrangian co-ordinate system.

In 3D stereoscopic DIC systems two cameras view the surface of the specimen. The camera system iscalibrated such that the relationship between raw and world space is known. By matching the patternbetween cameras and using the calibration model, the height and z-displacement of the surface canbe calculated. This depth perception system works like our eyes do.

3

Technique

StrainMasterDigital Image Correlation

Matching LocalSubset Pattern

3D Stereoscopic DIC

left camera

image

image

b

uL, vL uR, vR

P (xR, yR, zR)

right camera


4/12

The StrainMaster software features a simple workow enabling users to get reliable results quickly.

4 set-up aids including focus and dynamic range indication4 one view 3D calibration in less than 60 seconds, and advanced polynomial calibration modes for

congurations such as stereo microscopes4 accurately synchronized image and analogue input acquisition via the recording dialogue, or

import images from a standalone camera4 exible masking of the image to dene the zone(s) of interest4 choice of time-series mode, subset parameters, and calculation type4 ability to inspect the quality of the raw data before post-processing4 calculate strain (Lagrange, von Mises, Tresca)4 apply virtual extensometers and gauges to the surface4 generate a report or export (in formats includingMATLAB and ABAQUS)

In addition to the standard easy-to-use interface,StrainMaster benets from being built on the power-ful DaVis platform, providing extensive exible features which are needed in research environments.The batch processing mode allows the user to process multiple sets of images with pre-dened para-meters, and it is possible to include user dened macros. A wealth of processing functionality can be

found and utilized such as non-linear lters, smart algorithmic masking and much more.

Having acquired a set of results the user is able to automatically generate a report, read it directly intoMATLAB or export in specic formats

4 MATLAB Add-on4 ABAQUS

4 point cloud4 movies4 standard image and text formats

It is also possible to include any le (Word, Excel, PDF, PowerPoint) into your experimental DaVisproject.

4

Software

StrainMasterred su title missing

Advanced Processing

Two-way Interface


5/12

The DaVis platform offers complete hardware control, with no need to rely on home-made triggeringor separate multiple control programmes. It is possible to build acquisition loops and specializedtiming schemes.

4 standard and high-speed cameras4 data loggers for analogue data acquisition4 translation stages4 pulsed light sources

Phase locked recording of cyclic events such as fatigue testing is possible with theStrainMaster Controller, and post-triggering of high-speed events such as Split-Hopkinson pressure bar tests isstraightforward.

Operating in live mode, or as a post-process, it is possible to apply virtual extensometers or strain

gauges to the specimen surface. This virtual approach using optical techniques has several advan-tages over conventional mechanical devices:

4 non-contacting4 no need to choose extensometer position before the test4 is not damaged if the specimen fails4 can be used where the specimen is in solution or an environmental chamber

In live mode the strain output of the virtual extensometer can be outputted via optional 16 bit D/A con-verter as a scaled voltage, allowing the user to congure this in a strain control scheme. The beautyof DIC is that it allows comparison of extensometer and full eld data, often revealing that the full eld

data offers far more insight into the material behaviour.

A common use of full eld experimental data is to compare with and validate Finite Element simulati-ons. To facilitate this it is possible to export data in ABAQUS INP format, allowing the user to com-pare experiment and simulation within the ABAQUS post-processor, and even think about utilizingexperimental data as boundary conditions for the simulation.

StrainMaster includes a crack growth analysis module to identify and track crack development inmaterials, reporting crack length and crack opening. This module works with non-speckled surfacesand the standard StrainMaster hardware.

5

Software

StrainMasterFull Control

Finite Element Analysis

Crack Growth Analysis


6/12

The range of applications whereStrainMaster has been applied is vast, spanning all research sectorsand specimen scales, from microscale to metres. A few examples are shown here but further detailedexamples can be found in our separate application notes.

Composite materials are extensively used in aerospace and other high performance applications,particularly where speed and manoeuvrability are primary considerations. Full-eld data-rich imagingtechniques are used to provide a better understanding of the behaviour of composite materials sub-jected to high strain rate loading, such as those experienced during shock and blast loading.

The example shown comes from the University of Southampton where an Instron VHS test machinewas used for high strain rate testing of a composite specimen. A test methodology was also develo-ped to gather data synchronous with Infra-Red imaging techniques, and utilize Thermoelastic StressAnalysis (TSA) to make further calculations. This kind of data is invaluable in validating and optimizingcomputational simulations.

The performance of the materials used in the automotive industry, and of the components manu-factured using those materials is critical to safety, and an important factor in creating a light-weightfuel efcient design. With ever increasing emissions targets, automotive engineers need to investigateevery aspect of construction in modern vehicles, ecessitating a deep understanding of the integrity oftraditional and composite materials.

As well as investigating panel deformation or exhaust manifold expansion,StrainMaster can be uti-lized to investigate dynamic events such as tyre squash. This can even be done on a rolling road setupthrough the use of high-speed cameras or phase locked measurements.

6

Applications

StrainMasterred su title missing

Aerospace

Sample - tested to failure, courtesy ofDr. J. Barton, University of Southampton

Graphite is an important component in several currentand future design of nuclear ssion reactors, and thestructural integrity of the graphite moderator is criticalto the safe operation Advanced Gas Reactors (AGRs).Radiolytic oxidation degrades nuclear graphite strengthwhile fast neutron irradiation causes dimensionalchanges which in combination can cause damage to

the reactor core.

Digital Volume Correlation (DVC) was successfullyapplied to X-ray Computed Tomography images of nu-clear graphite. It allowed the calculation of full volumedisplacement and strain results, and enabled the crackopening displacement under load to be measured, re-vealing cracks before they can be identied in the rawimage.

Strain visualization of a stable crack in achevron notch test specimen, courtesyof Dr. J. Marrow University of Oxford

Energy

Automotive


7/12

DIC and DVC have been successfully applied to skin tissue, bone, teeth (see left) and implants.Biomechanical applications often require very small elds of view necessitating specialized optics.One such example is the study of Nitonol shape memory alloy which is used in endovascular stent

graft systems produced by Vascutek Ltd. By using aStrainMaster system equipped with a stereomicroscope it was possible to gain an understanding of the functional behaviour of small scale(< 0.5 mm diameter) Nitinol wire.

Digital Image Correlation can use the natural pattern of the material to identify defects before theyare visible to the eye, and in the example shown the lifting of a piece of problematic marquetry inlayhas been identied.

4 geological study of rock deformation4 structural health monitoring4 marine structures and components4 food and beverage industries

These two pages have given only a small selection of the possibilities and many more can be found inthe more detailed application notes available on the LaVision website.

7

StrainMasterBiomedical

Applications

Strain map on the surface of the specimen illustrating the compressive and tensile sidesof the wire, with eccentric neutral axis position, courtesy of Vascutek Ltd.

Analysis of implant-supported dentalrestorations, courtesy of Dr. R.Tiossi,

Dental School of Ribeirao Preto, University

of Sao Paulo, Brazil)

StrainMaster is well suited to civil engineeringapplications such as beam deection or crackpropagation in concrete. In the example on theright DIC has been used to identify the cracklocation within part of a concrete structure. Thenatural pattern of the concrete lent itself well to

the approach.

Historic furniture has very delicate materialswhich are susceptible to temperature and hu-midity changes; parameters which cannot al-ways be easily controlled in historic houses orold museum buildings. It is therefore benecialto be able to identify a strain hot spot on a pieceof furniture, fresco painting, or tapestry beforesignicant damage occurs.

Civil

Identication of cracks propagating throughconcrete, courtesy of Dr. J. Lord, NationalPhysical Laboratory

Arts and Conservation

Many more Applications

image courtesy ?


8/12

8

StrainMasterUpgrades and

Specialist Applications

AdvancedSolutions

Understanding of strain rate effects on material behaviour is important in the case of structures sub-ject to dynamic, shock, impact or blast loading. Full-eld data-rich imaging techniques are used toprovide a better understanding of composite, metal, and plastic material characteristics at high strain

rates. High-speed StrainMaster systems feature fully integrated high-speed cameras with kHz framerates.

Understanding the mechanical and material behaviour of microscale components is extremely chal-lenging and there is often a lack of detailed information on microelectronic or biomedical materialsin terms of stress-strain behaviour. LaVision offers stereo microscope based 3D DIC systems whichallow the user to collect and analyze full eld shape and strain in sub millimetre ranges. This informa-tion is extremely valuable in validating complex Finite Element simulations.

Measuring the strain response during loading at high temperature is a key capability for determiningthe mechanical and thermophysical properties of materials that are to be used at elevated tempera-tures. This topic is especially important in applications such as power generation, automotive en-gines, and gas turbine combustors, where the material may be operating beyond normal temperaturelimits. LaVision offer dedicated solutions for high temperature DIC measurements in terms of lighting,optics, and surface preparation

Small Scale Micro-DIC

High Temperature DIC


9/12

9

The dual level, two-sided calibration plates allow more than two cameras to be calibrated within asingle co-ordinate system. Together with the advanced PTU X controller, these cameras are accuratelysynchronized to obtain surface measurements from both sides of a panel, for example.

Interaction between air or water ow and a structure surface prole can result in a change in theuid ow path, which in turn causes pressure changes on the surface and can inuence the shape.This interaction between uid and structure may result in periodic or cycling instabilities which canestablish Fluid Induced Vibrations (FIV). LaVision offer systems which can simultaneously measureand quantify the uid and surface behaviour. By coupling our PIV and DIC technology we are able tomeasure the Fluid Structure Interaction behaviour.

Materials and components are oftensubjected to combined mechanicaland thermal loads, and it is essen-tial for design and test engineers tounderstand strain response duringthese combined loading scenarios.By combining an IR camera withthe StrainMaster system it is pos-sible record temperature and straindistributions and correlate the twoquantities. The StrainMaster soft-

ware can easily calibrate and inclu-de infra-red camera images withinthe project.

Multi-CameraMulti-Parameter

StrainMasterMulti-Camera Systems

for complex Surfaces andThickness Measurement

Fluid Structure Interaction (FSI)Combined Fluid Flow and

Surface Deformation

Combined Infra-Red Temperatureand Strain Measurements

thickness map of a pre-damagedcomposite panel


10/12

10

StrainMaster Digital Volume Correlation (DVC) is a powerful extension of DIC and provides full volume3D strain and displacement measurements. The materials natural or articially introduced internal patternis tracked between subsequent volumes, as illustated below for the case of a sand box tectonic plate

simulation. The obtained 3D full-eld displacement and strain maps allow the user to truly understandthe subsurface material behaviour and validate complex simulations, and in the case below visualizethe shear bands developing between the base and pop-up structure.

DVC is one of few full volume measurement techniques which can validate sub-surface strain behaviour

4 import from any volume imaging device with no volume size restrictions4 3-dimensional 3-component (3D3C) displacement eld in a complete volume4 identify cracks and discontinuities before they are visible in the image4 rigid body shift correction and volume alignment routines4 over 1 million nodes can be calculated per volume

4 advanced direct correlation with deformed interrogation volumes and multi-pass iterations.4 displacement precision better than to 0.01 voxels

Images are typically acquired from X-ray Computed Tomography (X-ray CT) systems, but can equallybe obtained by Magnetic Resonance Imaging (MRI), confocal microscopes, Optical Coherence Tomo-graphy (OCT) or via optical tomography for transparent media; for which LaVision offers its patentedTomographic reconstruction algorithms as an add-on.

Biomechanical subjects such as the study of bone implants are well suited to DVC due to the naturalinherent pattern, and DVC is able to determine the relative motion of bone and implant, for example.

The example above shows bone under compression. However DVC is suited to many other applicationsincluding granular ow and powder compaction, composite testing, foams, concrete and many more.

StrainMasterGoing beneath the Surface

Applications

Cutaway view of the reconstructed imageof the tube battery and vectors showing

dilation in the charged state

3D visualization of displacements through foamvolume (vector density reduced for clarity)

Use Volume Images fromX-ray Computed Tomography

E zz strain map for 1st, 3rd and 6th compression step, image courtesy of Dr. F. Gillard, BioengineeringScience Research Group, University of Southampton

i i

i l

i

i l

Compression rig

X-ray source

Rotational table

Complete experimental test setup with yellowarrow showing compression direction

Tomographic strain analysis of 3D XCT analogue experiment using Digital Volume Correlation (DVC)image courtesy of Dr J. Adam, Department of Earth Sciences, Royal Holloway University of London

Digital VolumeCorrelation


11/12

11

StrainMasterPortable

LaVisionsStrainMaster Portable is a compact and lightweight turnkey 2D and 3DDIC system forshape, deformation and strain measurement. Suitable for a huge range of applications where exibilityand portability is essential, LaVisionsStrainMaster Portable system is appropriate for a wide range

of subject sizes. It allows the user to quickly and easily obtain full eld data over the entire materialsurface. Building on customer feedback and our experience ofDIC use in the eld, together with ourknowledge of scientic and industrial applications of optical measurement systems, we have developedthe StrainMaster Portable hardware.

Standard 2D StrainMaster mounting system includes:4 heavy duty tripod for maximum stability4 1m lightweight horizontal rail4 1x camera gearhead on sliding mount4 1x LED gearhead on sliding mount

Standard 3D StrainMaster mounting systemincludes 2D system as above plus:4 additional 1x camera gearhead on sliding mount4 additional 1x LED gearhead on sliding mount

4 additional rails for long reach applications4 longer rails for larger camera separation4 test machine mounting systems4 adapter for vertical orientation

TheStrainMaster Controller sits at the hub of the system and controls all triggering and synchroniza-tion. The compact device features USB3 connectivity and can be mounted on the camera rail.The StrainMaster Controller comprises the following:

4 camera and pulsed LED power supplies4 synchronization board with ultra accurate

0.05 nansecond jitter between output lines4 A/D converter with 3 input and 2 output

lines (optional)

LaVision recognizes that research requires exibility in the system conguration in order to carry outchallenging and novel testing. We have a wide range of add-ons and accessories available includingspecialized lenses, speckle pattern application, and illumination.

4 a range of c-mount, f-mount, and specialized lenses4 illumination and lters for non-standard applications

including high temperature testing4 airbrush for ne scale speckle, pre-printed foils, and

special strain paint with exceptional elastic propertiesto avoid paint aking and cracking at high strains

StrainMasterCompact and Portable

DIC Systemwith Upgrade Flexibilty

Standard 2D StrainMaster

3D Stereo StrainMasterUpgrade

Optional Mechanical Add-ons

StrainMaster Controller

Accessories


12/12

Depending on the application LaVisionsStrainMaster systems integrate different lightsources and cameras:

LaVision Inc.211 W. Michigan Ave., Suite 100,

Ypsilanti, MI 48197 / USAe-Mail: [email protected]

www.lavisioninc.comPhone: (734) 485 - 0913

LaVision GmbHAnna-Vandenhoeck-Ring 19

D-37081 Goettingen / GermanyE-Mail: [email protected]

www.LaVision.comTel.: +49-(0)5 51-9004-0

LaVisionUK LtdDownsview House / Grove Technology Park Grove / Oxon / OX12 9FF / United Kingdom

e-Mail: [email protected]

Phone: +44-(0)-870-997-6532

StrainMasterSystem Components

Standard camera Model Features

Imager E-lite2M

Imager E-lite5M

compact, high sensitivity,high resolution CCD

cameras with a fastGigabit Ethernet interface

Imager X-lite 8MImager X-lite 11MImager X-lite 16MImager X-lite 29M

advanced progressivescan, fully programmableCCD cameras, high qualityimages, combined withhigh spatial resolution

High-speed camera Model Features

Imager MX 4M

cost effective, high spatialresolution CMOS camerawith 4 million pixelcombined with high framerates

Imager pro HS 4M4 million pixel, bestimage quality, fastestdata transfer

HSS 5.1HSS 6HSS 8HSS XHSS Z

1million pixel CMOS

cameras with kHzframe rates and highsensitivity

Phantom v411Phantom v711Phantom v341Phantom v641Phantom v1211Phantom v1611Phantom v2011Phantom v2511

Documents

BR StrainMaster 2015-Prelim