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Non-contacting Video Extensometers
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Non-contacting Video Extensometers
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Description
Measurement of strain during material testing is traditionally carried out using some form of contacting strain measurement device.
While providing accurate measurement in many applications, contacting extensometers can have an adverse effect on test results.
Non-contacting extensometry offers many benefits over traditional contacting devices including :
- No influence on the test specimen
- No problems with knife-edge slip
- No errors due to inertia of moving parts
- No moving parts eliminate errors due to wear
- No possibility of damage due to energy release at failure
- Can be used with environmental chambers over a wider temperature range
Principle of Operation
A high resolution digital camera and advanced real-time image processing are used to make precise strain measurements on material test samples. High performance is matched by an ergonomic design that allows easy set-up and provides very good operator access to the test area.
Strain is measured by tracking contrasting gauge marks placed on the specimen. The gauge marks can be in the form of dots or lines and they can be applied to the specimen by a variety of methods. Marking pens and target applicators are available as options.
The video image captured by the digital camera is transferred via an IEEE 1394 (Firewire) interface to the PC. Real time image processing algorithms running on the PC then locate the centers of the two gauge marks (or up to four marks if a transverse strain option is installed). Specimen strain is then calculated from the mark separation at the start of the test (gauge length) and the current mark separations. Tracking the center of the mark eliminates possible errors caused by stretching of the marks at high elongations.
Gauge length is automatically measured before the beginning
of each test and used for strain calculation, eliminating errors introduced by inaccurate specimen marking.
Two versions of the extensometer are available - Standard (SVE) and Advanced (AVE). The AVE offers greater accuracy for tests on rigid materials such as metals and composites and is also available with a tranverse measurement option for “r” value determination on sheet metals.
Both extensometers are fully supported by Bluehill software. Wizards allow easy set-up and calibration. Operators can calibrate the extensometer, enable and disable its use, and optionally define the area of interest to be measured. Once set-up is complete, acquisition of the marks defining the gauge length and the measurement of strain starts automatically when the test is started.
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Advanced Video Extensometer (AVE)
Application Range
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Non-contacting tensile strain measurement on a wide range of materials and specimen types including plastics, metals, textiles, paper, thin sheet, foil, wire
- Type of Loading: tensile, static only. Not suitable for high cycle dynamic fatigue tests
- Specimen shapes: round and flat specimens with or without shoulder tab ends
SVE Video Extensometer on Environmental Chamber
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| 2663-821 | Advanced Non-Contacting Video Extensometer (AVE) | Choice of 60mm,200mm, 500mm | Static |     |
| 2663-821J1 | 500mm Field of View kit | | | |
| 2663-821K1 | 200mm Field of View kit | | | |
| 2663-821L1 | 60mm Field of View kit | | | |
| 2663-821T1 | Transverse strain measurement option for 2663-821 | 5mm,25mm,30mm depending on field of view kit selected | Static | |
| 2663-822 | Standard Non-Contacting Video Extensometer (SVE) | Choice of 50mm,100mm,200mm, 350mm, 500mm | Static | |
| 2663-850 | Transverse strain measurement retrofit option for existing ... | 5mm,25mm, 30mm depending on field of view kit selected | Static | |
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