Published: 17 September 2014
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Cite this document
Often, it is desirable to combine both visual data with more traditional numeric data during a mechanical test. By definition, numeric values such as force, displacement, and cycle count are quantitative, while visual data is often difficult to use quantitatively. Visual data, however, is extremely useful in a qualitative sense. It can be used to verify deformation mechanisms and to validate test correctness in long-term, unattended automated tests. This paper presents two different methods for embedding visual data (static pictures and dynamic video) in standard mechanical tests. The paper discusses mechanical tests (tensile and fatigue) run using MTS' TestSuite mechanical testing software with commercially available cameras, and screen capture software. In a typical Fatigue Crack Growth test on a metallic alloy, static photos of the crack on one surface of a compact tension specimen are periodically acquired and stored to disk. In a fatigue crack growth test, the visual data can be used to verify other crack length measurement techniques such as compliance or direct current potential drop (DCPD). In a typical tensile test, video of the entire test is stored along with an embedded Picture in Picture of the stress-strain curve. This technique can be used to correlate interesting features on the stress strain curve with necking behavior during the test.
video, photos, fatigue crack growth
Schwarzkopf, E. A.
MTS Systems Inc., Eden Prairie, MN