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.

 

Dynamic loading on a wind turbine blade and resin bridges

Analysis of a wind turbine blade

The test panel was an original section of a wind turbine blade with a defect (a foam block with bridges). Previously the defect was located by infiltration of color through small drilled holes. The sample is examined non-destructively by the SE-Sensor.

 

Section RotorBlade-a  Section RotorBlade2

left: Set-up

right: Time average result at frequency of 2569Hz showing the debonding area.

 

 

 

 

Section RotorBlade3Section RotorBlade4left: Live view of surface including shearing.

right: Time average measurement from the marked area in the live image.

 

 

 

De-bonding of resin bridges

A GFRP sandwich with foam blocks and resin bridges should be examined. The detection of the defect type und structure is very quick and reliable in this case, because the defects are visible, not only at their local natural frequencies, but also due to their forced deflection shapes over a wide frequency bandwidth.

Section2 RotorBlade

 

The excitation frequencies of the selected measurements are 1398 Hz (1), 3133 Hz (2), 2442 Hz (3) and 4906 Hz (4) – numbering in following images:

Section2 RotorBlade2
 

Vakuum loading on battery packs

Air inclusion or air pockets in modern Li-battery packs is a serious and dangerous problem. The isi-sys SE2 sensor is able to detect tiny and large defects such as air bubbles, air pockets, cracks and other within a second. The defects can be far below or near to the surface. An example of a battery pack (test sample from University of Munich, IWB) and the measurement result is shown below.

Test setup:

The test has been done by SE2 sensor in combination with a glass vacuum chamber for a simple manual test. This is an economic solution for spot NDT by manual service. For automated series test in production different setups are required.

Test pocedure:

The battery packs are tested by small pressure differences of some mbar, which can be applied in seconds or below in small chambers. The sensor is monitoring the surface of the battery pack while the pressure is changed, measuring the differential deformation of the surface. Due to the expansion of the air bubbles and air pockets, the air inclusions can be located such as shown in the following images.

The first image shows the live view of the battery pack from the sensor. The second shows the recontructed phase, which is corresponding to the local deformation gradient.

battery pack3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

battery pack2

Generally the required pressure difference depends on the defect depth, defect size an the mechanical stiffness of the tested structure, but in general the load is small due to the high sensitivity of the sensor detecting differential deformations of the surface.

Operation mode analysis on a mobile phone during vibration alert

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Reference coordinates and contour of the mobile phone.

 

 

 

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This article describes the measurement and analysis of the operation deflection shapes and rigid body vibration motions of a mobile phone excited by its vibration alert. The mearurement is done, using a non contact, 3D, full-field, high speed stereo image correlation system in combination with the new Vic-3D FFT module analyzes the recorded deformation data in the frequency domain by phase-separation method.

Nokia

The measured deformations and displacements during the vibration alert are evaluated against the reference state for each stereo image pair. In this case the recording time covers about 5,5 seconds with 1000 FPS corresponding to about 5500 single measurements.

The following figure show the average vibration amplitude U.

 

Nokia2

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.

Challenges

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.

Solution

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
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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.

Bremsen3

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.