Almost all tensile testing standards such as ASTM and ISO require strain measurement. The best suited extensometer for an application depends on the requirements set forth by the standard as well as the material properties of the specimen.
Every industry has specific requirements for accuracy, resolution and the measurement range of an extensometer. ZwickRoell designed and developed extensometers that cover every application, from strain-controlled metals testing to high extension rubbers or structural steel. Specimen gauge lengths can be from 1.5 mm to 1000 mm. Contact and non-contact extensometer options are available for tests at high temperatures including for high-temperature furnaces up to 1200°C. In addition, ZwickRoell offers extensometers that can monitor width reduction or deformation during compression and flexure testing.
A distinction is generally made between contact and non-contact extensometers that are used for measurement of extension, change in width, or strain measurement.
- Contact measurement can be carried out with a clip-on extensometer, which has at least two probes or knife edges that are placed onto the specimen. As the specimen extends, the distance between the two knife edges changes thereby indicating the specimen extension.
- Optical extensometers are used for non-contact measurement.
The information that follows will provide you with more details on our contact and non-contact extensometers and their applications.
These extensometers are used for direct extension measurement in tensile tests, flexure tests, and alternating load tests. Clip-on extensometers and extensometers with sensor arms are in direct mechanical contact with the specimen via knife edges positioned at right angles to the gauge length.