Catalogues - extensometers-for-material-testing-machines

Catalogue Extensometers for material testing machines

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Zw/ck # Roell

4. Contact measurement systems

4.1 Sensor arm extensometers

Zwick offers a wide range of sensor arm extensometers. This starts with a basic extensometer for use with the „zwicki" test machines and ends at fully automatic extensometers.

Interchangeable knife edges

The knife edges are also easily replaceable. They consist of straight and convex sides. They can be simply rotated so that the knife edges will always be in single-point contact to the specimen (Flat or round specimen, see fig. 5), thus ensuring extremely precise measurements.

These extensometers are used for direct extension measurement at tensile, compression, flexure or alternating load tests. They all have a large measurement range that can be steplessly adjusted corresponding to the specimen to be tested.

Function description

The Zwick sensor arm extensometers work with incremental measurement systems. Transmission of the extension to the measurement system takes place via play-free, tiltable knife edges on the sensor arms. The sensor arm clamping forces are very small and can be steplessly adjusted so that specimen are not damaged, and so that the knife edges are located perfectly.

Interchangeable sensor arms

The easily replaceable sensor arms (See fig. 4) enable these extensometers to be adapted to the test type, the material to be tested and to the specimen shape. A plug-in connection enables sensor arms for tensile or flexure tests, or fork sensor arms as well as extended sensor arms for use in temperature chambers to be mounted quickly and simply. This system reduces replacement, interchanging and equipping times to a minimum.

Fig. 5: Round specimen with straight knife edges, and flat specimen with convex ones

Knife edges with vulkollan surfaces for notch sensitive specimen and knife edges with corundum surfaces for extremely smooth specimen are available thus enabling the optimum knife edge to be used for all materials.

Measurements can be run through to specimen break without any risk of damaging the sensor arms: The knife edges (They can be tilted by 180°) only transmit extremely low forces to the sensor arms at specimen break, whereby damage to the sensor arms and the extensometer at specimen break is reliably prevented (See fig. 6).

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Fig. 4: Different types of sensor arm increase the range of application

Fig. 6: Principle function of the tiltable knife edges