videoXtens High Precision 

videoXtens HP sets new standards in accuracy and reproducibility.

videoXtens HP is the perfect solution where international standards require high accuracy. Operator influence is virtually eliminated and consistent test results are assured. 

videoXtens HP is a non-contact, high-resolution extensometer developed for tests which require maximum precision.

videoXtens HP extensometer

Key Advantages and Features

Advantages and features

Large field of view thanks to innovative technology

videoXtens HP includes two high-resolution cameras. Their overlapping fields of view are combined into one large field via Zwick Roell array technology. Markings leaving the field of view of one camera are automatically transferred to that of the next camera. This provides a greater field of view with high resolution.

The flexible tunnel can be extended or retracted to suit individual requirements. By minimizing environmental influences it creates the conditions required for a low-noise signal.

Comprehensive range of functions

  • Automatic gage-mark recognition and acquisition of initial gage-length L0.
  • Exact synchronization of all measurement channels.
  • Environmental influences (e.g. air currents, variations in lighting) minimized by the flexible bellows tunnel.
  • Optimum, uniform specimen illumination by LEDs incorporated into the tunnel.
  • Strain-controlled tests are possible.
  • Specimens with structured surfaces can be measured via pattern recognition with no need for additional marks.
  • Entire test sequence can be followed on-screen.
  • Video capture: specimen recording synchronized with measured curve for retrospective viewing of test.
  • Wear-free (= low maintenance) system.

Reliable test results

High resolution and measurement accuracy

  • Accuracy Classes 0.5 and 1 as per EN ISO 9513
  • Accuracy Class B1 as per ASTM E83 from a gage mark distance of 15mm
  • Calibration requirements for tensile modulus values as per ISO 527-1, Annex C.

As the system employs non-contact measurement, material characteristic values are unaffected. Operator influence is also minimized, ensuring consistent test results.

Measurement of tensile modulus on plastics to ISO 527-1

ISO 527 initially requires Accuracy Class 1 as per ISO 9513 for the extensometer. This is satisfied when a relative display deviation of ±1 % or an absolute display deviation of ±3 µm is achieved, depending on which value is greater (see graphic). videoXtens HP satisfies the requirements of Accuracy Class 0.5 with a display deviation of <±0.5% or <±1.5 µm.

However, that is not yet sufficient to satisfy ISO 527-1 including determination of tensile modulus. The requirements specified in ISO 527-1 are considerably more demanding: tensile modulus is determined at extensions of 0.05 % and 0.25 % of the initial gage-length. According to the standard this change in gage length must be measured to an accuracy of 1%.

Applications

Plastics

  • Tests on plastics to ISO 527­1 or ASTM D638, including accurate measurement of tensile modulus values (see graphic below)

Fiber composites

  • Tensile tests on filament strands and laminates of fiber composites, e.g to ISO 527-4/5, ASTM D3039, ASTM D4018
  • In-plane shear tests (±45° method)
  • Tests up to break possible with no damage to extensometer, even with brittle-fracturing specimens

Metals

  • Also satisfies accuracy requirements for tensile tests on metals to ISO 6892-1 (not closed-loop strain-rate control).
  • Option for determination of strain distribution and strain at break as per Annex H of ISO 6892-1.
  • Biaxial measurement: simultaneous extension plus change-in-width measurement possible.

Specimen marking

In the case of materials with smooth, monochrome surfaces the gage length is marked using a felt-tip pen or by means of self-adhesive gage-marks. Alternatively the specimen can be prepared by applying a pattern spray to the surface area. Extension is measured using the pattern created by the texture applied at points on the gage-length. Specimens with a structured surface can be tested even without additional marking; the surface texture serves as a natural pattern.

No extra marking is required for optional change-in-width measurement. Measurement is via a special edge-detection algorithm (Second Measurement Axis option).

The transverse-contraction gage-length can also be set by applying dots or by selecting areas of a natural or artificial pattern on the specimen surface.

Due to gage-length compensation the same degree of accuracy is not required when applying gage marks at distance L0 as with other fine-strain measurement methods. This eliminates error sources while speeding up test preparation.

Technical overview

videoXtens High Precision

Item No.

1007443

Type

videoXtens HP (2 cameras)

Initial gage length L0

5 to 75

mm

Displacement measurement, max.

FOV - initial gage-length

Resolution per FOV [when attached to]:

128 mm [zwickiLine]

0.25

µm

128 mm [table-top testing machine, test-area width 440 mm]

0.25

µm

145 mm [table-top/floor-standing testing machine, test-area width 630/640 mm]

0.3

µm

Distance between extensometer reference plane and center of test axis:

zwickiLine

410

mm

table-top testing machine, test-area width 440 mm

410

mm

table-top/floor-standing testing machine, test-area width 630/640 mm

530

mm

Measuring frequency, max. (adjustable)

62.5

Hz

Max. test speed

1000

mm/min

Weight (incl. tunnel), approx.

10

kg

testXpert II minimum version

V 3.2

Accuracy

Accuracy Class 0.5 as per

EN ISO 9513

Accuracy Class B1 from gage length 15 mm as per

ASTM E83

Young's modulus measurement: subject to measurement recommendations, the measuring system satisfies the requirements of

ISO 527-1

  • Scope of delivery:
  • measuring head with two digital cameras
  • 2 objective lenses, f = 35 mm
  • tunnel for minimising negative environmental conditions (e.g. air currents)
  • software for image acquisition and evaluation
  • accessory case with alignment and marking aids

A free slot in testControl / testControl II is required for the INC module (included in delivery). Can be mounted on zwickLine and AllroundLine; from testXpert V3.6.1 onwards, with test Control or testControl II. Not in conjunction with Windows 10.
Cannot currently be used with temperature chamber (no mounting, as chamber would foul tunnel).

Software options 

testXpert II testing software offers various options for precise, traceable non-contact extension and strain distribution measurement. 

Test Re-Run and strain distribution

The optional Test ReRun module enables retrospective recalculation of strain on the basis of an image series recorded during a test, using a different initial gage-length (provided multiple markings are present). This can be particularly advantageous in component testing, for example, when it is necessary to evaluate local strain at different locations, or in standard tensile tests when specimen necking has occurred outside the original initial gage-length.

The recalculated strain can naturally be synchronized retrospectively with the other measured values via testXpert II.
This option is available with testXpert II Version 3.4 onwards.

The Strain Distribution option enables determination of local strains at multiple measuring locations along the specimen gage-length. These are available as channels in testXpert. Up to 16 measuring locations are automatically recognized and evaluated during the test. This option also allows automatic real-time symmetrical adjustment of the initial gage-length around the necking (as per ISO 6892-1, Annex H).

Video Capturing

The testXpert II Video Capturing software option is recommended if recording of the test is additionally required (without retrospective recalculation). The recording is synchronized with the measured curve, enabling the test to be viewed retrospectively. The option includes no hardware, as recording and synchronization take place entirely via the videoXtens system.
This option is free of charge.

2D dot matrix

This option allows two-dimensional measurement of dots applied to a planar specimen surface. This enables determination of local strains and specimen inhomogeneities under load. X and Y co-ordinates plus the distances between dots are available as measured values.

Up to 100 measurement dots can be measured in any desired arrangement or in matrix form. Display in testXpert II is limited to 15 channels.

This option uses only one camera for measurement; any other cameras present are switched off beforehand.

Optional second measurement axis 

This option allows biaxial measurement; transverse strain (e.g. change in width) can be recorded at the same time as longitudinal strain. Alternatively, change in width can naturally be measured alone.

  • Two versions are available for measurement of transverse strain:
  • measurement directly on the specimen edge with no additional markings (required for determination of r-value); a backlight is required for this version
  • measurement on the specimen surface using dot markings or sprayed-on pattern; with this version specimen illumination is via incident light.

Deflection measurement 

videoXtens can also be used for flexure tests. There are several options for measuring specimen deflection, depending on the type of test and the specimen condition and properties:

  • measurement using incident light via marks on the specimen
  • measurement using backlight on the specimen lower edge
  • measurement of deflection in the test axis or of the polynomial approximation of the curve.

Maximum deflection that can be measured: with videoXtens the maximum deflection corresponds to the FOV; with videoXtens Array to 1/3 of the total FOV (deflection is measured with one camera only in this case).

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