Ways to Measure Strain

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Contacting

Strain measurement in materials testing is traditionally carried out using some form of contacting extensometer. A typical clip-on extensometer, for example, attaches to the specimen with clips or elastic bands and uses knife-edges to accurately track deformation in a specimen during testing.

While providing accurate strain measurement in numerous applications, contacting extensometers carry some inherent disadvantages; and therefore,it is highly recommended that the user review the section on "Considerations when Choosing an Extensometer" and carefully consider all aspects of the testing application before selecting the proper device.

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Non Contacting

Several methods of non-contacting strain measurement exist, ranging from the most basic method of measuring displacement of the crosshead to full-field strain mapping using Digital Image Correlation (DIC). It is highly recommended that the user carefully consider all aspects of the testing application and review the section on "Considerations when Choosing an Extensometer" before selecting the proper device.

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Bonded Strain Gauges

Most clip-on contacting extensometers use strain gauges to measure strain on the specimen, but to achieve higher accuracy the strain gauge itself can be applied directly to the surface.

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Special Use