NIST (National Institute of Standards and Technology) using Vic-3D for digital image correlation (DIC)

NIST is using the Vic-3D digital image correlation (DIC) system to analyze stress in bridges. By using DIC, they try to understand the impact of stresses and strains on the metal connectors of bridges in order to avoid damage or failure.


NIST is pre-straining a wide plate with digital image correlation (DIC) to determine the small-scale specimen sectioning plan:

https://www.nist.gov/video/pre-straining-pipeline-steel-plate


NIST is conducting a CWP test with digital image correlation (DIC) to determine local and remote strains used to determine the Tensile Strain Capacity of a flawed pipe girth-weld:

https://www.nist.gov/video/curved-wide-plate-testing


NIST is making an SE(T) test with digital image correlation (DIC) showing the asymmetric strain gradient of a specimen notched in the heat-affected zone:

https://www.nist.gov/video/single-edge-notch-tension-testing

DIC measurements on structural concrete

The ETH Zürich – on of our longstanding customers – provides on the following website their research project. They analyse the accuracy of digital image correlation within the scope of reinforced concrete. To the project members belong Prof. Dr. Walter Kaufmann and Dr. Jaime Mata Falcón.

 

eth-zuerich-2Full field strain measurement in rebar tension

test: failure phase.

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.

 

Deformation Measurement

The following video clips show a deformation- or strain-measurement of a metal spring element, measured by using Vic-3D.

The first deformation measurement would be made in the X direction.

 

The second deformation measurement would be made in the Y direction.

 

The third deformation measurement would be made in the Z direction.

 

In the last case you see the result of the strain measurement.

Motion Measurement on Rear Swinging Fork

The video shows the application of a stereo image correlation (phase synchronized) for a three-dimensional displacement measurement or movement analysis (Vic-3D).

The used stereo camera system is based on two 5 Mpixel cameras with a frame rate of 6Hz (at full resolution) in combination with the isi-sys synchronisation and trigger device for stroboscopic opservation of periodic events.

X

Four measurement areas (hydraulic cylinder – below, wheel hub – left, swingarm – middle and linear unit – right above) with specle pattern were monitored for the evaluation. The vector arrows represent the current displacement state.

 

Combination Stereomicroscope and Vic-3D digital image correlation

Application examples of a special stereomicroscope in combination with Vic-3D digital image correlation on electronic components.

Stereomikroskop

Image 1: Measurement setup

Measurement set up: Stereo microscope mounted on x-y-z-microtable (backside) and tensile machine (right).

Stereomikroskop2

Image 2: Strain in x-direction

Stereomikroskop3

Image 3: Strain in y-direction

Strain distribution of a half cut capacitor-chip (left part) and its soldering area (round section). The board is under
bending load. The board is vertical on the right sight of the image. The local red area is showing a crack in the
soldering part. Image area approx. <2mm.

 

Lötkugel

Image 4: The main strain of measuring a solder ball d=300µm under horizontal shear stress is shown.