laserXtens Compact Offers High-Precision Measurement

These single-camera measuring systems are ideal for testing small to very small specimens. 

  • In contrast to contact-type extensometers or pure video instruments, laserXtens Compact / Compact HP can measure strains on mini and micro-specimens with short gage lengths and diameters from 0.5 mm with high accuracy.
  • The measurement principle used requires NO gage marks and there is no contact during the test. The system is highly accurate and easy to operate.
  • laserXtens Compact HP features resolution of 0.04 µm. Any measurement inaccuracies occurring as a result of possible lateral movement of the specimen are minimized by the telecentric imaging.
  • laserXtens Compact HP even increases measurement accuracy by compensating for lateral specimen movement, which may easily occur with small, non-rigid specimens.
laserXtens Compact HP

Overview of laserXtens Systems

Application description

Extensometers using laserXtens systems provide non-contact measurement of deformations on a wide range of materials.

The measuring principle eliminates the need to apply gage marks, giving laserXtens systems a wide range of application.

  • Tensile, flexure and compression tests on metals and plastics.
  • Tests on components.
  • Tests on specimens where specimen contact is undesirable or not possible due to specimen condition or properties.
  • Deformation measurements on specimens prone to whipping at break which might damage a contact-type measuring system.
  • Testing possible in temperature chambers and at high temperatures.
  • Applications requiring biaxial deformation measurement.

With laserXtens high-resolution systems, measurements on small specimen geometries are easy. Flexibility and ease of operation make laserXtens equally suitable for classical quality assurance applications or for use in research and development.

Advantages and features

  • High precision and resolution
  • laserXtens possesses high precision in the micro and macro measurement ranges.
  • laserXtens HP satisfies the requirements of Class 0.5 of ISO 9513 (Class B2 of ASTM E83).
  • Even the smallest specimens can be measured
  • Specimens from 1 mm in width/diameter can be tested; smaller specimens may also be possible following pre-testing.
  • In contrast to contact-type extensometers or pure video instruments, laserXtens can measure strain on short specimens (gage lengths from 1.5mm) with high accuracy.
  • No specimen contact - no specimen marking
  • laserXtens has no contact with the specimen; measurement is not influenced by the laser light.
  • Specimen marks are not required. This saves time, especially with high specimen throughput.
  • laserXtens can be mounted at varying distances from the specimen. One advantage of this is that it can be used in temperature chambers, where application of gage marks can be very difficult due to environmental conditions.
  • Easy to use in automated systems also - no manual specimen preparation required.
  • laserXtens can also measure transverse strain with no need for additional markings; biaxial measurement is possible.
  • Unrivaled functions and options
  • laserXtens HP can be used for strain-rate-controlled tests to ISO 6892-1 Method A1 (closed loop) (for gage lengths ≥ 50 mm).
  • laserXtens Array HP can be used for strain-rate-controlled tests to ISO 6892-1 Method A1 (closed loop) (for gage lengths ≥ 30 mm).
  • Optional upgrade for determination of r & n-values to ISO 10113 and ISO 10275.
  • laserXtens is integrated into testXpert III testing software. Use of a separate monitor is recommended to enable the live image from laserXtens to be observed parallel to the testXpert III display.
  • Matrix option allows two-dimensional measurement at up to 100 measuring points distributed arbitrarily or in matrix form over a planar specimen surface. This enables determination of local strains and specimen inhomogeneities.
  • Another software option allows determination of strain distribution at multiple measuring points along the specimen gage-length. It is also possible to determine strain at break as per Annex H of ISO 6892-1 (laserXtens Compact and laserXtens Array HP only).
  • Specimen deflection can optionally be deternined in 3 and 4-point flexure tests. Measurement can be carried out at one or three points (with a maximum measurement base of 15 mm).

Specimen range

laserXtens
  • The following specimen types can be tested using laserXtens:
  • All types of flat specimens made of plastic and rubber with a thickness of 0.5 to 12 mm
  • Flat specimens made of metal with a thickness of 0.1 to 30 mm
  • Round specimens made of metal with a diameter of >1 mm to 30 mm

laserXtens systems consist of measuring heads with digital cameras and laser light sources.
The specimen surface is recorded using full-frame digital cameras, while the specimen is illuminated with laser light. The laser light is coherent and dispersed on the specimen surface. This creates a speckled pattern highlighting the specimen surface in the camera image.

The speckled pattern is like a type of fingerprint of the specimen surface. These patterns can be used as virtual gauge marks. Thereby framing areas by evaluation fields and defining the measuring points on which surface movements should be measured.

When a load is applied to the specimen, the virtual gauge marks move. The laserXtens tracks these virtual gauge marks using a highly developed correlation algorithm. This process is known as speckle tracking.

laserXtens' software calculates the strain on the specimen from the relative displacement of the virtual gauge marks and its initial state at the start of the measurement.
Two or optionally more virtual gauge marks can be defined in the image, as standard.

Important notes

laserXtens was developed for use with a majority of the classical materials and testing requirements.

Various physical considerations mean that reliable operation of laserXtens requires observance of a greater number of general conditions than when using contact-type extensometers.

  • The specimen surface must reflect enough laser light to generate sufficiently well-formed speckle patterns. This is the case with most metals and plastics. If necessary simple aids can be used to improve conditions on the specimen surface.
  • The specimen must be fixed firmly in the center of the test axis in order to minimize movement out of the measurement axis.
  • A low-vibration environment is necessary for safe, reliable, accurate operation (laboratory conditions).

All specimen gripping systems which hold the specimen firmly in the center of the test axis are suitable, e.g. hydraulic, pneumatic and screw grips.

In the case of plastics, pre-testing is necessary to determine the reflective properties of the material.

Pre-testing also allows the Zwick Testing Laboratory to assemble the optimum configuration for your particular application. The properties and condition of the specimen surface (reliable measurement signal, resolution), the specimen grips in use (elimination of out-of-plane movement) and the measurement travel required are all checked. Zwick guarantees reliable operation of laserXtens on the basis of pre-tested specimens and testing conditions (= process reliability).

Notes on use with temperature chambers and high-temperature furnaces

When laserXtens HP and laserXtens Array HP are used in conjunction with temperature chambers and high-temperature furnaces it should be noted that the change in optical conditions for testing will have a negative effect on the measurement signal. This basically concerns air currents in the temperature chamber / furnace and outside on the viewing port / furnace port. To minimize these effects the air flow around the specimen must be smoothed and the air currents near the viewing / furnace port minimized by means of optical tunnels. These solutions are designed and produced on a custom basis. Due to the dimensions of the temperature chamber, laserXtens is in this case mounted at a greater distance from the specimen, with consequent changes in resolution and accuracy class (technical details available on request).

Technical Overview

laserXtens Compact & Compact High Precision

laserXtens Compact/Compact HP

Measuring head with 1 digital camera incl. lens ( f = 75 mm), 1 red laser light source, software for image acquisition, evaluation of cross-correlation and transfer to testXpert testing software, accessory case with calibration tools

Type

laserXtens Compact

laserXtens Compact HP for zwickiLine

Item No.

1001574

1001580

Laser safety class

2[1]

2[1]

Initial gage length

  • 3 to 13 mm with test-area width 440 mm
  • 3 to 17 mm with test-area width 640 mm

3 to 14

Measurement travel

  • up to 13 mm L0 via speckle tracking, with test-area width 440 mm, then switch to flow measurement test mode
  • up to 17 mm L0 via speckle tracking, with test-area width 640 mm, then switch to flow measurement test mode

up to 15 mm L0 via speckle tracking, then switch to flow measurement test mode

Resolution

0.15

0.04

µm

Accuracy

Class 0.5

Class 0.5

to EN ISO 9513

Typical measurement frequency (adjustable)

100

70

Hz

Max. measurement speed at measurement point

250

250

mm/min

Specimen thickness

flat specimens

≤30

≤30

mm

round specimens

1 to 30

0.5 to 30[2]

mm

  1. No protective measures required.
  1. Pre-testing is required for specimens with thickness < 1 mm.

laserXtens HP operates with testXpert II or testXpert III only and in combination with testControl and testControl II. testXpert II Version 3.2 or above is required with testControl. testXpert II Version 3.4 or above is required with testControl II.

A free slot is required in testControl II.
The required tC RS module or INC module is already included in delivery.

Software Options for the laserXtens Extensometer

Strain distribution

The Strain Distribution option enables determination of local strains at multiple measuring locations along the specimen gage-length. Evaluation of up to 16 measuring locations is possible. This option also allows automatic real-time symmetrical adjustment of the initial gage-length around the necking (as per ISO 6892-1, Annex H).

Second measurement axis

This option allows local transverse strain to be measured simultaneously with determination of longitudinal strain.

2D dot matrix

This option allows two-dimensional measurement of dots on a planar specimen surface. This enables determination of local strains and inhomogeneities of the specimen 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 III is limited to 15 channels.

Deflection

laserXtens also determines deflection in 3 or 4-point flexure tests. This can be measured at one point (displacement of one measurement location) or three points (relative displacement of the middle or two outer measurement locations) with a maximum measurement base of 15 mm (20 mm for laserXtens Array HP).

Life-saving precision: testing memory alloy stents

High-accuracy tests in the micro range are a tough nut to crack. As well as being sensitive, the specimens are too small for contact-type measuring systems and the results must display high micro-level accuracy. Admedes Schuessler solved the problem with a laserXtens Compact HP, a Zwick laser extensometer featuring non-contact operation based on innovative technology.
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