U.K.’ Imetrum (North American distributor is Respec, Rapid City, SD) has launched what is reportedly the first non-contact video extensometer capable of achieving the exacting requirements of ASTMD638 and ISO527-1 equivalent for measuring tensile properties of plastics.
Following rigorous, independent testing, Video Gauge has been shown to be capable of accurate determination of the tensile modulus be measuring a change of gauge length within accuracy of 1% of the relevant value. In tests, Imetrum was able to achieve between 0.2µm to 0.3µm (7.87 x 10(6) to 1.18 x 10(5)) for all gauge lengths using the same camera and lens combination—over three times the accuracy required by ASTMD638/ISO527 for 50mm (1.97 in.) gauge length.
Designed for use with tensile testing machines, the new system comprises a controller with sophisticated Video Gauge software, one or more high-resolution digital video cameras and an appropriate lens for the application. Also included is a voltage output module for interfacing with traditional strain channels, lighting, a tripod, and a rugged case for storage and transport. One of its key advantages over clip-on extensometer methods is that the Video Gauge avoids the problem of knife edge slippage where the knife edges can potentially cur into a specimen and induce a failure point. This system can complete a test through modulus and on to failure, eliminating the need to stop the test and remove clip-on extensometers.