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AutoX 750 automatic contacting extensometer

News International-French

21 May 2013

Instron’s AutoX 750 automatic contacting extensometer supports the execution of testing routines including tension, bending and compression, and delivers more reliable and more accurate materials data in shorter time.

Instron’s AutoX 750 high accuracy of +/-1 µm, along with a maximum travel of 750 mm and multiple knife edge options make it an ideal extensometer for tensile, flexure and compression testing of various materials including highly rigid composites, metals, and plastics.
With features including automatic gauge length positioning and automatic attachment to the test specimen with adjustable contact force, the AutoX 750 can enhance the productivity of testing laboratories. By removing tedious and time-consuming manual steps, lab operators can have a simplified testing routine while improving throughput. Reducing inconsistencies in how a traditional clip-on extensometer is attached improves the repeatability and reproducibility of critical test results.

Thanks to its high accuracy the AutoX 750 meets the strain measurement specifications of ASTM E83, ISO 9513, and ISO 527-1 (2011). It is fully compatible with closed loop strain control and complies with ISO 6892-1 Method A and ASTM E8. Instron’s Bluehill 3 software package is used to record and store the data supplied by the extensometer and determine a variety of calculations including modulus, offset yield, and plastic (non-proportional) elongation to failure. The AutoX can be used with both fully-automated or manual testing systems, such as Instron’s 3300, 5500, and 5900 electromechanical dual column systems, and LX, DX, HDX, and KPX static hydraulic testing systems.

Patent-pending features of the AutoX include: the simultaneous opening and closing of both arms via a rotating common bar with just one motor, making the arms lighter; a debris shield to protect the extensometer from damage due to the ingress of dirt/debris; and an ergonomic tensioner to adjust the gripping force of the measurement arms. Thanks to its construction the AutoX can stay attached to the specimen through failure.

When not in use, the mounting allows operators to quickly and safely position the extensometer out of the test area providing a safe storage environment for the device. Removing the AutoX from the test area allows operators to easily switch out grips and fixtures without the additional step of uninstalling the device.

Tailor-made setups boost benefits for testing composite laminates
The modulus values of typical composite materials are high and strain to failure low. Thus the measurement of strain in composites tensile testing (e.g. AITM 1-0007, ASTM D3039, EN 2597, ISO 527-4/5) requires high accuracy. The AutoX 750 extensometer is capable of meeting these challenging requirements, as shown in a particular case, where 250 kN precision wedge grips were used on an Instron 5900 series frame. Instron’s Bluehill Software was used for data recording. Utilizing the automatic nature of the extensometer allowed the user to increase throughput while maintaining a high level of repeatability and accuracy throughout the duration of each test.

Using automatic extensometry for tensile testing of composite tow specimens according to ASTM D4018 provided precise results in spite of their irregular cross section  and delicate nature. The tests were conducted using a 5900 Series electromechanical frame, along with pneumatic side-action grips. The AutoX 750 automatic extensometer provided accurate data with reduced operator influence and improved productivity.

ASTM D695 is a commonly used method to determine the properties of composites, including modulus, compressive strength and maximum compressive strain. A proven setup is the combination of a 5900 series testing machine, two 50 mm diameter hardened-steel compression platens, a D695 compression fixture, and an AutoX 750 attached directly to the specimen to measure strain all the way to failure.

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