Strain measurement using laser extensometry in a temperature chamber

laserXtens, Zwick’s latest strain measurement system has successfully been used for applications in temperature chambers where materials are typically exposed to temperatures from -70 to +250°C whilst being subjected to tensile or compressive loads.

Such tests are very important for the automotive industry where the measurement of both axial and transverse strain is often required. laserXtens measures bi-axial strain without any specimen contact and without the need to attach any marks to the specimen. Part of the specimen surface is illuminated using the principle of laser speckle interferometry. As the specimen is subjected to load the reflected speckle pattern is tracked by two digital cameras, and highly advanced real-time software algorithms convert this data directly into strain.

The tests carried out in the temperature chamber revealed that this measurement technology was not adversely affected by the thin layer of frost which had formed on the specimen. The speckle pattern was easily detected and could be tracked during the tests.

Only a window is required in order for laserXtens to “see” the specimen inside the temperature chamber so laserXtens offers significant benefits in terms of its ease of use. Meeting class 1 of ISO 9513 (class B2 – ASTM E83) the extensometer remains outside the testing environment and measures strain up to failure. Zwick believes that this device will revolutionize the measurement of strain on specimens under environmental conditions.