Image Correlation for Shape, Motion and Deformation Measurements discusses the fundamentals, theoretical improvements, and practical applications of digital image correlation (DIC). This book is a collaboration of decades of research and development of 2D and 3D digital image correlation software. This research has been implemented into our products and provides in-depth explanation of quantitative measurement techniques.

Correlated Solutions, Inc. has served the worldwide test and measurement industry since 1998 through the development of advanced, non-contact, full-field measurement systems. Our staff has over 100 years of combined research and development experience of optical measurement techniques. We continue to develop new and innovative products for the test and measurement industry, while providing solutions to more applications than ever before. The quality of our products, technical support, and customer service has played a key role in our success.

Correlated Solutions manufactures a variety of turn-key digital image correlation measurement systems that allow users to quickly and accurately make extremely detailed measurements of surface shape, motion, deformation, vibration, and strain without any mechanical contact with the sample. Specimens of virtually any size under any loading condition can be measured with high resolution and accuracy. Full-field 2D and 3D data is displayed in the form of contour plots, animations, graphs, and even in real-time. All data can easily be extracted and exported in various standard formats for FEA validation.

Correlated Solutions has also developed digital volumetric correlation (DVC) software VIC-Volume, which analyzes images from X-Ray sources to quantify internal strain measurements of objects under static loading.

Introduction 5

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Table of ContentsTechnology Overview...................................................................................................8

VIC-2D Overview.......................................................................................................10

VIC-3D Overview.......................................................................................................14

VIC-3D SR/HR/XR/CL...............................................................................................18

VIC-3D HS/UHS........................................................................................................ 22

VIC-3D HS FFT.........................................................................................................28

VIC-3D Micro.............................................................................................................32

VIC-3D EDU..............................................................................................................36

VIC-3D Modules....................................................................................................... 38

VIC-Gauge 2D/3D.....................................................................................................40

VIC-Volume (DVC)....................................................................................................44

VIC-Snap Remote.....................................................................................................48

System Accessories..................................................................................................50

Contact Us................................................................................................................55

Technology Overview 9

Digital image correlation is an easy-to-use optical measurement technique that utilizes high-quality, machine vision, digital cameras to measure deformation on an object’s surface. The method tracks the full-field movement of a random high-contrast speckle pattern applied to the sample’s surface with sub-pixel accuracy. DIC has been repeatedly proven to be accurate when compared to tradition devices such as strain gauges and extensometers, and is the number one tool for validating FEA models. Our turn-key DIC systems utilize this advanced optical measurement technology with the highest accuracy and speed in the industry. Systems are fully integrated with a variety of high-resolution and high-speed digital cameras with streamlined acquisition software for easy synchronization of external data from load frames or any other analog outputs, even for extremely dynamic testing. Our software analyzes images captured from high-resolution low-speed and high-speed digital cameras, IR cameras, scanning electron microscopes (SEM), atomic force microscopes (AFM), and even X-Ray machines or CT scanners.

Various configurations allow our DIC measurement systems to be used for material testing, structuraltesting, microscopy testing, vibration/fatigue analysis, vibration analysis, volumetric measurements, and much more. DIC systems are ideal for mechanical testing applications in the automotive, aerospace, chemical, and biological industries. These systems are widely used in government laboratories and universities for both research and education. We offer a wide variety of flexible and robust DIC systems that are customized to fit your applications, needs, and budget. We offer systems that provide solutions to new problems.

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VIC-2D Overview 11

The VIC-2D system utilizes optimized digital image correlation algorithms to provide full-field displacement and strain data for testing planar specimens. In-plane displacements are measured with sub-pixel accuracy within the measurement area, and a variety of strain tensors are computed within the software.

The Vic-2D software computes in-plane displacements down to 1/100th of a pixel, and strains from 100 microstrain to 2000% strain and above with 20 microstrain local resolution. Specimens ranging from 10 mm to >100 m can be measured utilizing standard optics, and specimens down to the nanometer scale can be measured utilizing microscopy devices such as SEM and AFM systems. Setup is simple, specimen preparation is fast, and no special illumination or lasers are required.

Vic-2D is offered as a complete turn-key measurement solution or as a software only package for integration with your existing hardware. Our turn-key systems are customized to your applications and the analysis software is simple to operate and easy to learn.

• Full-field in-plane displacements & strains

• Local velocities & strain rates

• Automatic start point detection

• Intuitive AOI editor

• Create custom variables with Apply Function feature

• Rigid body motion removal tool

• In-plane rotation computation

• Time filter options

• No calibration required for strain computation

• Sample size from nanometers to >100 m possible

• 1/100th pixel motion resolution

• Down to 20 microstrain resolution

• Synchronized analog data acquisition

• Easy data exporting (csv, stl, ACII, Matlab, etc.)

VIC-2D SYSTEM FEATURES:

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Data Courtesy of University of Michigan

Figure 1. Test setup & strain data overlay

Figure 2. Data extraction from DIC

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VIC-2D HS Example 13

Ultra-High Performance Concrete (or UHPC) is a material that has gained much attention for its durability and extremely high strength. It is a specially formulated concrete that is capable of achieving extremely high performance with compressive strength in excess of 150 MPa. When properly reinforced with steel fibers, the material is capable of achieving strain hardening behavior with strains at peak stress of up to two orders of magnitude greater than that of regular concrete and exceptional energy absorption prior to fracture. Research has suggested that the material is particularly promising for impact and blast applications.

To gain a better understanding of strain distribution in UHPC, the researchers at the University of Michigan performed high speed impact tests using the VIC-2D HS digital image correlation system. The Photron SA-5 high-speed camera was utilized at a resolution of 320 x 264 pixels and 75,000 frames per second to measure a strain rate of 126 s-1. Coupled with stress signals obtained using other techniques, the researchers could accurately characterize the complete stress-strain response of their specimens. The stress-strain curve can be seen on the left.

Dr. Sherif El-Tawil of the Civil & Environmental Engineering Department states, “The VIC-2D system is very user friendly and straight forward to use. We could not have completed our tests as quickly as we wanted without it, and only the DIC technique can give us the spatial distribution of strains at high strain rates that we desired.”

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The VIC-3D system is a powerful turn-key solution for measuring full-field shape, displacements, strains, velocities, and much more of an object’s surface in three dimensions. The VIC-3D system includes all necessary software, hardware, training, and technical support to ensure systems operate without any problems right out of the box. Systems are customized to fit your needs for a wide range of applications including quasi-static, dynamic, thermal, vibration analysis, and microscopy, to name a few.

Vic-3D can measure full-field displacements and strains from 100 microstrain to 2,000% strain and above for specimen sizes ranging from <0.7 mm to >100 m. Setup is simple, requiring only a quick and easy calibration procedure and an applied random speckle pattern. No special illumination or lasers are required and there is no contact with the specimen during testing.

VIC-3D Overview 15

Full-field 3D displacements & strains

Integrated marker tracking

Local velocities & strain rates

Intuitive AOI editor

Create custom variables with Apply Function feature

Rigid body motion removal tool

In-plane rotation computation

Time filter options

Sample sizes from micrometers to >100 m possible

1/100th pixel motion resolution

Down to 20 microstrain resolution

Intelligent large scale calibration - no need for impractical large calibration targets

Calibration disturbance correction feature

Synchronized external analog data

Easy data exporting (csv, stl, ASCII, Matlab, etc.)

STANDARD VIC-3D FEATURES:

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VIC-3D SR/HR/XR/CLVIC-3D SR/HR/XR/CL are our flagship turn-key systems that include acquisition and post-processing software with standard resolution (SR), high resolution (HR), extra-high resolution (XR), and CameraLink (CL) cameras to meet your testing needs. Various interfaces are available, such as USB 3.0, Firewire, GigE, and CameraLink, with each offering their own specific benefits in terms of resolution, acquisition rate, and triggering capabilities. Resolutions up to 29 MP and frame rates up to 250 Hz are supported with our integrated solution.

VIC-3D HS/UHSVIC-3D HS and VIC-3D UHS include all the benefits of VIC-3D with added capabilities for high-speed (HS) or ultra-high-speed (UHS) image capture. VIC-3D HS and UHS systems are fully integrated with Vic-Snap HS/UHS image capture software. Vic-Snap simplifies the image capture process, ensuring stereo images are synchronized for calibration and testing. Furthermore, Vic-Snap integrates a DAQ system for easy analog data synchronization. Frame rates from 1 KHz to 5 MHz are achievable. DAQs may not be available for all image capture rates.

VIC-3D HS FFT VIC-3D HS FFT combines the dynamic measurement capabilities of VIC-3D HS with a patented software module for measuring operational deflection shapes (ODS’s) from transient vibration events. The system is capable of measuring amplitudes with nanometer resolution and with a large dynamic frequency range. This true full-field ODS measurement system can be used for transient events or to measure frequencies from impact responses. Frequencies up to 50 KHz are achievable.

VIC-3D MicroThis unique system utilizes a patented Stereo Microscope Distortion Correction software module which removes complex non-radial optical distortions. Without this correction, strain measurements can be severely biased. The system can be equipped/outfitted with up to 5 MP resolution cameras and up to 2,000 Hz frame rates or a zoom range from 0.7 mm to 7 mm. Automated stage control and streamlined calibration procedures make this the most robust 3D DIC Microscopy system on the market today. Coupled with a precision tensile tester, measurements are more accurate than ever before.

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VIC-3D SR/HR/XR/CL Overview 19

VIC-3D SR/HR/XR/CL is our flagship turn-key systems that are available with standard resolution (SR), high resolution (HR), extra-high resolution (XR), or CameraLink (CL) cameras to meet your application needs. These systems are perfect for quasi-static applications, and also fatigue/vibration applications using the Fulcrum module (see page 38). Our systems are extremely flexible, as we support cameras with interfaces such as USB3, Firewire, GigE, and CameraLink, with each offering their own specific benefits in terms of resolution, acquisition rate, and triggering capabilities.

Due to the flexibility of these quasi-static VIC-3D systems, data can be collected in a wide range of settings with ease including laboratory tests, large structural testing, and even in the field. Applications range from material coupon testing to complex thermal applications with IR camera integration (see page 39.) Vic-3D offers additional capabilities such as real-time processing, remote control triggering, and much more. Full-Field measurements are processed on-the-spot or can be performed on any Windows PC with the included post-processing license. Camera Resolutions up to 29 MP (XR) and frame rates up to 250 Hz (CL) are available and all have real-time processing capabilities.

Includes all features listed in the VIC-3D Overview section on page 14

All VIC-3D systems include Vic-2D software at no additional cost (see page 10)

Optional full-field real-time processing up to 10 Hz available

Compatible add-on products: VIC-Gauge 2D & 3D (page 40) and other modules listed on pages 38-39

VIC-3D SR/HR/XR/CL System Specifications:

VIC-3D SR/HR/XR/CL SYSTEM FEATURES:

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Data Courtesy of Dr. Kenneth Perry, EchoBio, LLC.

Figure 1. Experimental setup usingthe VIC-3D System

Figure 3. Change in radius contourunder load from expanded stent.

Figure 2. Speckled silicone tubewith stent inserted.

Figure 4. 3D change in radius contour plot showing displacement vectors.

VIC-3D SR/HR/XR/CL Example 21 Medical device manufacturers have the responsibility to create and maintain efficient and safe products to keep the world population healthy. Dr. Kenneth Perry of EchoBio LLC is an industry leader and expert on the experimental validation of implantable medical devices. Recently, Dr. Perry was tasked with evaluating the radial force profile of a braided, self-expanding stent for use in correcting blocked blood vessels. Dr. Perry specifically needed to examine how the radial force changed from the end of the stent to the middle of the stent. This quantitative data is critical to the proper design and function of the stent, and Digital Image Correlation was the only technology commercially available that could provide the measurements needed at the required accuracy. Dr. Perry utilized the VIC-3D system to make such measurements with valiant success that could potentially revolutionize the medical device industry.

Dr. Perry began his experiments using perfectly straight silicone tubes that were custom made to have mechanical properties similar to a blood vessel. His experimental setup is shown above in Figure 1. The experiment involved deploying the stents into the tubes and measuring the resulting deformation. Dr. Perry knew that any simplified point or line measurement on his samples would have been misleading. This is where the VIC-3D system enters the experiment and provided Dr. Perry with the full field data he needed to be confident in his measurements and publish accurate results for his client.

The silicone tube was prepared for the experiment by having a speckle pattern applied by using off the shelf spray paint. The area of interest was masked off and a white base coat applied. The black speckles were then simply added by using an over spray technique with black spray paint. Figure 2 above shows the speckled silicone tube with the stent inserted.

The change in radius variable and resulting contour plot was the most valuable data for Dr. Perry because it clearly shows the largest force is located near the end of the stent. This contour plot, shown above in Figure 3, also indicates areas of larger radial force that could have gone unnoticed using traditional measurement techniques.

Not only did Dr. Perry obtain full-field displacement data, he was also able to easily quantify the radial force profile of the stent and show the circumferential variation that resulted from the underlying woven stent structure. Figure 4 above shows the displacement vectors of the stent in a full-field 3D contour plot. The displacement vectors show the magnitude of the resulting deformation which allows Dr. Perry to easily interpret the data as well as publish professional results for his client. The VIC-3D system gave Dr. Perry the ability to measure with confidence.

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VIC-3D HS/UHS Overview 23

The VIC-3D HS turn-key system is a non-contact measurement solution for dynamic events. It offers users unmatched speed and accuracy for a wide range of applications. From simple drop tests to complex excitations, this system can measure a wide range of dynamic events. Applications include (but are not limited to) crash testing, ballistic events, rotating objects, split Hopkinson bar tests, burst tests, air bag deployment, fracture mechanics, and much more. The system combines the premier digital image correlation software Vic-3D with the fully-integrated acquisition software Vic-Snap HS. Vic-Snap HS streamlines the entire setup and testing process. By including features that make image acquisition quick and easy, users can acquire calibration images and set triggering options with the touch of a button. High-speed cameras with various dimensions, light sensitivities, frame rates, and high-g models are available with each system.

The VIC-3D UHS turn-key system utilizes the fastest cameras on the market for ultra-high-speed DIC applications, which may include explosive testing, high-velocity particle acceleration, and ceramic fracture research, to name a few. This system is capable of frame rates up to 5 MHz and VIC-Snap UHS will save an abundance of time during setup. Triggering becomes extremely challenging at these speeds, so image acquisition precision is paramount to a successful test. The system is completely supported by our technical staff and is installed by our engineers.

*We offer a wide range of high-speed cameras. Please contact us for specif ic technical and pricing details.

VIC-3D HS/UHS System Specifications:

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Figure 1. VIC-3D HS Test Setup

Figure 2. Contour image overlay of transverse strain at t = 4.4ms.

Data Courtesy of Ohio State University

VIC-3D HS Example 25

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. Utilizing high-speed cameras, the VIC-3D HS system can be used to quantify the surface displacements and strains in the three dimensions over the entire field with great precision. DIC has gained widespread popularity over recent years in such high-speed applications due to its high accuracy, flexibility and ease of use.

In this example, a 6 mm diameter cylindrical specimen was compressed at a strain rate of 50 s-1. The VIC-3D HS system was used to capture the surface displacements and strains on the specimen during the event. Figure 1 shows the test setup with high-speed cameras focused on the specimen. A random speckle pattern was applied to the surface that allows the analysis software to easily track the deformation with sub-pixel accuracy. Although the high-speed cameras are capable of much higher rates, for this test they were set to a frame rate of 14,000 fps to maximize spatial resolution while acquiring an adequate number of images during the event. The cameras were post-triggered at a resolution of 1024 x 400 pixels. After the event, the images were transferred to the computer’s hard drive, and then post-processed using the VIC-3D analysis software. Figure 2 shows a full-field contour plot of the transversal strain (Exx) overlaying the raw image at t = 4.4 ms. The compressive strain observed was found to be non-uniform.

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Data Courtesy of University of Texas at Arlington

Figure 5. Peak minor strain before failure

Figure 4. Peak shear strain before failure

Figure 3. Peak major strain before failure

Figure 2. Glass/epoxy material being tested

Figure 1. HPV-X2 Cameras

VIC-3D UHS Example 27

Prof. Andrew Makeev and Research Engineer Brian Shonkwiler at the University of Texas at Arlington Mechanical and Aerospace Engineering department operate a dynamic DIC testing laboratory. Together they conduct a variety of DIC tests ranging from quasi-static to extremely dynamic testing. In this particular example, the VIC-3D UHS system coupled with two Shimadzu HPV-X2 cameras were used to measure dynamic properties of a glass/epoxy material. The purpose of this short beam shear test was to measure multiple material properties, such as shear & axial modulus and shear strength.

The images were acquired during the event, downloaded, and then post-processed with VIC-3D. The frame rate for this test was 666,667 fps with a 200 nanosecond exposure. The specimen was speckled using a permanent marker, and an extremely bright stroboscope was used to illuminate the specimen. The impact velocity was 10 m/s, and the specimen reached approximately 3.5% shear strain at failure as shown in Figure 4.

“The purpose of the impact test is to determine how the dynamic characteristics of the material properties differ from the static properties. The importance of using the VIC-3D system is the fact that there are steep strain gradients on the face of the specimen. We would never get the strain information we need using a strain gage.” - Brian Shonkwiler, University of Texas at Arlington.

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Operational deflection shape (ODS) measurements of an aluminum plate obtained using the VIC-3D HS FFT system

VIC-3D HS FFT Overview 29

The Vic-3D HS FFT Vibration Analysis system is an addition to the Vic-3D product line of measurement solutions which enables full-field 3D viewing, measurement, and analysis of operational deflection shapes that occur from transient events. These shapes can easily be viewed and analyzed with amplitudes in the nanometer range. Three-dimensional displacements, strains, veloci-ties, and accelerations are all computed for thousands of data points for any given frequency. The result is not only visual, but users can export the data for FEA analysis and validation.

The VIC-3D HS FFT system takes the vibration analysis to the next level by seamlessly integrating the capability to measure transient events with visualization. Since the technique provides full-field displacement data, no scanning of the object surface is required, shortening acquisition times. The acquired images are then post-processed to compute full-field amplitude/phase vs. frequency data.

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VIC-3D HS FFT Example 31

Automobiles are subject to many forces during 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 heavy-duty 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 FFT Vibration Analysis system. Amplitudes as small as 40 nanometers were measured at a frequency of approximately 2,000 Hz. The graph to the left illustrates the average out-of-plane amplitude A(w) as a function of frequency. Three unique shapes can easily be identified at 120, 932, and 2,087 Hz.

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VIC-3D Micro Overview 33

Flexible zoom range

Automatic system calibration with provided fixture

Integrated ring light for diffuse specimen illumination

Custom beam splitter for optimized imageoverlap and focusing

High-quality airbrush painting system for easy specimen preparation

Precise and computerized 3-axis stage movement for easy focusing and positioning

Customizable coordinate system

User friendly data inspection tools

Point cloud data exporting in common formats

Precise node data extraction for FEA comparison/validation

Create custom variables with Apply Function feature

Accurate full-field 2D and 3D measurement of shape, displacements, and strains of the test article

Flexible data extraction of statistics, time-history from points or regions, line-slices, and much more

HARDWARE FEATURES:

The VIC-3D Micro system measures three-dimensional surface shape, deformation, and strain data that can be viewed on microscopic specimens. This unique system utilizes a patented stereo microscope distortion correction software module which removes complex non-radial optical distortions that can severely bias strain measurements.

SOFTWARE FEATURES:

Shape data of optical flat without distortion correction

Shape data of optical flat with distortion correction

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*Camera resolutions and frame rate vary upon configuration.

Figure 5. Eyy at maximum loading

Figure 3. Eyy at maximum loading with user defined line

Figure 2. Eyy at maximum loading

Figure 6. Load vs. Global Eyy

Figure 4. Eyy development within user defined line

Figure 1. Test Sample with indicated area of interest

Data Courtesy of University of Vienna

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VIC-3D Micro Example 35

To prepare the digital image correlation system for testing, two 5.0 MP monochrome cameras were mounted to Correlated Solutions’ specially designed beam splitter. The beam splitter mounts to a zoom body and provides rigid mounting for the stereo-rig as well as easy adjustment capability so that independent image overlap, focus, and stereo angle can be achieved. Attached to the zoom body is an objective lens with a fitted ring light. The stereo microscope system mounts to a 3-axis motorized or manual precision translation stage for exact position control.

The copper dogbone specimen was soldered together at the center of the gauge area. The solder region was 82 microns in thickness. The dogbone width was 3.0 mm, but here, a 1.0 mm region on the edge was analyzed so strain distribution through the solder could be investigated. This region is indicated in Figure 1. The sample was loaded in tension until failure and images were taken about every 2lbs of applied load.

During the test, 23 image pairs were analyzed so that strain development could be observed and analyzed. Figures 3 and 5 show the y-axis (strain in the tensile loading direction) at the last image taken before failure.

Data extraction tools in Vic-3D enable the user to investigate global or user-defined local areas. Any of the variables may be extracted into plots and tabular data. In Figure 3, a line is drawn throughout the solder interface in the high strain region. Figure 4 displays the average y-axis strain within the user defined solder region. The red line in Figure 4 displays the strain for the last image taken before failure and the gray lines demonstrate how that strain developed throughout the test.

Load data was recorded through an analog signal and plotted against variables for global and user-defined local regions. Figure 6 displays the load vs. strain graph for the average global strain.

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VIC-3D EDU 37

The VIC-3D EDU system is a low-cost solution developed for academic institutions to assist in teaching the digital image correlation technique to undergraduate and graduate students. The VIC-3D EDU system utilizes the same accurate algorithms as VIC-3D with streamlined acquisition, calibration, and post-processing capabilities. The system is perfect for courses such as solid mechanics, measurements, automotive design, aerospace, safety, CAD/FEA, civil engineering, and many others. This affordable simple setup with a sleek design includes all necessary hardware and software for easy implementation into any syllabus. The system includes stereo mounted cameras in an enclosure with an integrated LED light source, tripod, tripod head, unlimited VIC-3D EDU software licenses, and supporting material for an easy and quick setup. The system simply requires a computer with one available USB 3 port. Whether teaching students new measurement techniques or measuring material properties, this system will surely enhance the quality of any department’s curriculum.

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The VIC-3D Real-Time processing module allows full-field 3D test data to be displayed live from streaming images while the test is running. Users can freely choose the data density for processing rates of 2-10 Hz.

Real-Time

The VIC-3D Fulcrum Module allows low-speed cameras to capture displacement and strain measurements during periodic events. This add-on module can provide a low-cost alternative to purchasing high-speed cameras.

Fulcrum

All VIC-3D systems come with free integrated marker tracking. This allows users to track individual points using ellipse or bow-tie style markers.

Marker Tracking

VIC-3D HS FFT is two systems in one. It allows users to measure deformation and strain from dynamic events. The Fast Fourier Transformation (FFT) module adds the capability to measure Operational Deflection Shapes (ODS) from transient vibration events.

VIC-3D IR provides full-field temperature and 3D deformation data without contacting the sample. All imaging devices are intelligently calibrated, which enables temperature and deformation data to be placed in a common coordinate system. This integrated system is the perfect solution for almost any thermal application, such as CTE measurements.

VIC-3D IR

VIC-3D Fusion is a turn-key system that includes multiple camera pairs which allow users to measure more surface area. Systems can be configured to image large areas, complex geometries, and opposite sides of a specimen.

VIC-3D Fusion

VIC-3D Modules 39

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The VIC-Gauge 2D system utilizes optimized 2D digital image correlation algorithms to provide real-time displacement and strain data for mechanical testing. An unlimited number of virtual strain gauges and extensometers can be placed on a live image on the specimen, which are then monitored in real-time. Data from each gauge or extensometer is saved, and up to two may be selected for output via the included data acquisition system. The deformation data may be plotted live against analog inputs, and full resolution images may be saved concurrently for full-field analysis in Vic-2D.

VIC-Gauge 2D/3D Overview 41

The VIC-Gauge 3D system is offered as a turn-key strain measurement solution or as an add-on to the VIC-3D full-field measurement system. While Vic-Gauge 2D is limited to in-plane measurements, Vic-Gauge 3D measuresout-of-plane displacements by utilizing two stereo mounted cameras to perform a three-dimensional analysis on a pair of images in real-time. The measurements are displayed graphically, but can also be outputted via an analog voltage for strain control. The system utilizes the same robust algorithms included in the VIC-3D system.

The real-time analog outputs allow for mechanical tests to utilize DIC as a method to control a test using the DIC data. Vic-Gauge can measure arbitrary displacements and strains from 100 microstrain to 2000% strain, with a measurement resolution of ~50 microstrain for specimen sizes ranging from <5 mm to >10 m.

VIC-3D Gauge System Specifications:

*Faster recording rates available at reduced camera resolutions and other interfaces

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VIC-Gauge 3D Example 43

Wing tip devices, or “winglets”, on an aircraft serve to reduce drag by recovering vortex energy at the tip of the wing. This increases the lift generated at the wing tip by creating a more efficient airflow over the upper wing near the tip, consequently reducing lift-induced drag. Wing tip devices improve the lift-to-drag ratio, which increases an aircraft’s speed, range, and fuel efficiency. Because less fuel is needed to operate them, substantial cost savings can be obtained from a winglet’s implementation on new aircraft or retro-fitting to existing aircraft.

Aircraft design and test engineers are particularly interested in wingtip joints because this is the primary area where computer models (FEA) predict peak strains. However, physical testing is required to confirm that results fall within the parameters predicted by models. Real-time measurements obtained from the VIC-Gauge 3D digital image correlation system are an excellent way to validate expected results because the software allows the user to control the test with variables that are outputted from the DIC system. For example, testing the winglet with a load cell controlled with strain can speed up the validation process by ensuring samples stay within their elastic range and do not fail.

In this example, a mechanical bending test was performed on a scaled Boeing 747-400 model to replicate in-flight vortex forces sustained by a winglet joint. A stepped point-load was applied from the outside of the winglet’s tip toward the fuselage, which caused the winglet joint to experience a compressive load comparable to those created by vortex forces.

VIC-Gauge 3D was utilized to measure and output strain at the most critical location along the joint. In the test images the resultant displacement and strain are displayed next to the virtual gauge: 1.1 mm and -0.7% respectively. The displacement values u (x), v (y), and w (z) and remaining strain variables are shown together below the image. The plots to the right of the test images update in real-time, which are outputted via the integrated DAQ system (e.g. 1% strain = 1 volt). This allows the user to create a closed-loop system where the strain or displacement outputs could control the test parameters.

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VIC-Volume (DVC) Overview 45

Vic-Volume is a digital volumetric correlation (DVC) software platform that analyzes images from X-Ray or CT Scanners to measure internal deformation of a specimen under an applied load. Vic-Volume analyzes the acquired images to create three-dimensional volumetric displacement and strain data of the specimen’s internal behavior. The result is a full-field contour plot of the deformation data that can be viewed, animated, and extracted for FEA validation. Common applications include characterizing rubber components in the automotive and aerospace industries.

Volumetric 3D displacements & strains

Semi-automatic initial guess computation

Optimized for accuracy using a non-linear filter optimization method to reduce bias and interpolation artifacts

Convenient AOI selection method

Highly optimized code for fast analysis time

Advanced memory managementpermits analysis of huge volumetric data sets

STANDARD VIC-VOLUME FEATURES:

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Figure 4. FEA Ezz Strain DataFigure 3. VIC-Volume Ezz Strain Data

Figure 2. Load frame

Figure 1. Diagram of CT inspection using line detector

VIC-Volume (DVC) Example 47

The diagram in Figure 1 displays a typical setup of how images are acquired during a test. The scanner acquires images at specific depth coordinates, and then Vic-Volume analyzes the image slices to construct a 3D volume made up of voxels. The individual voxels are the building blocks for the sub-volume, which contain the volumetric image correlation data. In this example, a torus is mounted between two grips, and a set of reference images are acquired from a CT scanner at known increments. Each ‘slice’ of data is then analyzed to compute a static volume measurement. After the puck undergoes a compression load, images are acquired again by the CT scanner at the same locations. VIC-Volume’s correlation algorithms are used to calculate the volumetric change at each subset of voxels, which shows the user through strain and deformation values.

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Setup. Control. Acquire.

VIC-Snap Remote 49

The VIC-Snap Remote application is a convenient way of controlling the cameras without being connected to a computer. With this application, the user can detect & control multiple VIC-Snap systems with a single wireless device.

With the VIC-Snap Remote application the user can conveniently view live images on a mobile device or tablet while setting up the cameras. This enables the user to speed up an already simple setup and calibration process with features like pinch to zoom, image alignment with cross-hairs, and exposure control to optimize image quality. The VIC-Snap Remote application is compatible with most iOS and Android devices and is offered free with VIC systems.

• Single user remote calibration

• Remote camera triggering for image acquisition

• Complete exposure adjustment and control

• Over exposure indicator

• View gray scale histogram for full screen viewing

• Pinch-to-zoom live images

• Double tap images for full screen viewing

• Toggle crosshairs for easy alignment

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Whether working with C-mount cameras or F-mount cameras, high magnification or low magnification, long working distances or short working distances, a specified selection of lenses and adapters will achieve almost any desired field of view.

Lenses

To achieve the most accurate data possible, it is crucial that stereo cameras are rigidly mounted relative to one another. Standard and customized mounting solutions are available.

Mounting

Cool LED lighting is generally recognizedas the best lighting solution for most DIC applications. LEDs provide cool, continuous illumination, and are now bright enough for most high-speed applications. Lighting systems that are specifically designed for low-speed and high-speed DIC applications are avail-able. Low cost LED and halogen systems are also available.

Lighting

System Accessories 51

It is imperative that the DIC system’s optics and sensors stay clean to avoid inaccurate data. The lens care kit is included with all turn-key systems, and is an excellent accessory to ensure the optics and/or sensors are cleaned correctly when needed.

Large scale or potentially dangerous applications often require the cameras to be mounted far apart from each other or far away from the acquisition computer. USB, Firewire, and Ethernet repeaters, extenders, and hubs area available to overcome virtually any long range triggering challenges.

Long Range Triggering

The VIC Speckle Pattern Application kit substantially reduces noise and bias caused by poor sample preparation. The kit includes various dot-size rollers and stamps that allow the user to apply the perfect speckle pattern for the camera resolution and field of view combination, ultimately improving results.

VIC Speckle Kit

Lens Care KitS

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Macro Calibration Targets

Large-Scale Calibration

IR Calibration

Dual-Sided Calibration

CSI has designed a calibration technique for large scale applications that does not require oversized calibration targets. This provides a very accurate, low cost, and practical solution to what may initially seem like a “large” problem.

These targets are pre-calibrated to

allow users to precisely migrate data from two VIC-3D systems positioned opposite one another. This provides measurements of the initial thickness and through-thickness strain of tensile coupons.

For small scale calibrations, CSI provides laser etched, blue chrome plated, sodalime glass calibration grids. They are compatible with external hardware, such as grid fixtures or positioning arms for stabilization so they can be used for higher magnification applications.

The VIC-3D IR system utilizes chrome plated glass or laser-etched anodized aluminum targets to calibrate the IR camera’s intrinsic and extrinsic parameters. This calibration enables temperature and deformation data to be placed in a common coordinate system. Measuring material CTE could not be easier.

VIC-3D Calibration 53

The VIC-3D Calibration Targets are fabricated from an aluminum sandwich material with a polymer core providing ultimate rigidity. The calibration targets are now coded, enabling the analysis software to automatically detect the spacing of each target, increasing the overall robustness and ease of use of the VIC- 3D system. The ultra-matte finish makes it virtually impossible to show highlights, even under direct lighting or large tilts, which improves calibration scores. Some targets have a reduced marker size and increased number of markers, which improves calibration results for high resolution cameras. The targets are also waterproof and can be cleaned with standard household non-abrasive cleaners or with regular dish soap and water. Customized target sets are now available for low resolution cameras, such as ultra high-speed cameras. Lastly, smaller borders reduce the overall size, which enables the targets to fit into tight spaces more conveniently.

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Notes

Copyright © 2017-2018 Correlated Solutions, Inc.

The material printed in this catalog remains property of Correlated Solutions, Inc., and

may not be sold or distributed without written permission from Correlated Solutions, Inc.

Contact Us 55

SalesEmail: Sales@CorrelatedSolutions.comPhone: (803) 926 - 7272 Ext. 1

SupportEmail: Support@CorrelatedSolutions.comPhone: (803) 926 - 7272 Ext. 2

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