In this application video, a 3-cam (5 Mpx) FlexDIC system is used to measure the peak strain that occurs at fracture of a coupon in a tensile test. The real-time, speckle pattern quality evaluator is shown in all three of the camera images. The configuration of the load cell as an analogue input is shown, whereby both the units, dimensions, and scale can be selected. Additionally, the analogue input values are sampled/filtered between camera frames, known as Analogue Inter-Step Sampling (AISS).
As can be seen, the analogue channel fluctuation significantly reduces when AISS is activated. An online calibration is then performed, with real-time feedback of the calibration quality. Thenafter, a recording procedure is selected from one of the available templates. The recording starts when 1N is overcut, acquiring every 5th image (at 30 Hz) equally 6 images/second. As soon as the coupon fractures, and the load drops below 5 N, 39 images are taken (at the 30 Hz rate) before the 5 N limit is undercut. (This is equivalent to a pre/post trigger)
The correlation evaluation is performed with a mask and the selection of the center (middle) camera as the reference camera. This is known as the Central Reference Camera Perspective (CRCP). During the startpoints search, it is clear that the facet/subset distortion is lowest in the middle camera. This concept allows 3-camera systems to achieve 30% higher accuracy, compared to 2-camera systems.
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