Sheet metal testing applications require calculations such as yield strength, yield point elongation, ultimate tensile strength, plastic strain ratio ('r' value) and the strain hardening exponent ('n' value). These calculations place a high physical demand on traditional contacting extensometers for measuring axial and transverse strain to allow for enough travel to test the specimens through break, but small enough gauge lengths to ensure high accuracy in measurements. Additionally, relevant ASTM and ISO testing standards have accuracy requirements that must be achieved.
We have found that video extensometry is not frequently used in these applications, as most customers in the metals industry use traditional contacting extensometers and trust the reliability of the results. Developments in the technology of extensometry offer metals testing customers other options, such as our Advanced Video Extensometer (AVE). Not only does this solution allow for simultaneous collection of axial and transverse strain data, and reduce the maintenance required for wear and tear on knife-edges, it may also increase productivity and simplify testing. The purpose of this test is to demonstrate the accuracy and reliability of the AVE for testing steel specimens. For this test, we used our 5982 universal testing system, with a 10 kN load cell and 50 kN wedge grips with serrated faces. We captured the test results with our Bluehill® materials testing software.