In this application video, a 3-cam 5 Mpx FlexDIC system is used to measure the shear strain XY and
effective (von Mises) strain of a 3D-printed Coupon with Rectangular Cut-Outs in Istra4D V4.12.
In the projection calibration, the QR-code of the 10mm Calibration Target is recognized and detected
automatically via Istra4D. Each calibration target has its own encrypted QR-code which states the
calibration target’s inherit ID and properties. During the online calibration, the projection calibration
model is computed and updated with a live feedback status.
Using the ringbuffer recording mode, 698 frames are saved pre-trigger and 2 frames are saved
post-trigger at the current acquisition speed of 50 fps. As such, the pre/post-trigger is acquired
after the specimen has already fractured.
Users can watch the recording before saving the images in the playback mode.
In the correlation evaluation, using the Central Reference Camera Perspective (CRCP), the definition
of the reference subset/facet shape can be selected in any of the three cameras. The central or
middle camera serves as the best reference for the reference subset/facet shape definition since it
is most perpendicular (no stereo angle) to the object and as such, the subset/facet shape is least distorted.
Another feature used in the correlation evaluation, is the Auto-Detect Optimal Facet/Subset Size,
which automatically selects the optimal facet/subset size to be used in the correlation based on the
size & distribution of the speckles in the reference image.
In the graphical visualization, the 2D-overlay of the shear strain XY can be seen that shows the generation
of strain around the middle area of the coupon where the sample eventually fractures. A temporal plot is
also created using a virtual line gauge of the engineering line strain (in mstrain), Euclidean length change
(mm) and absolute load signal (in N). Using virtual polygon gauges at the lower, middle and upper areas,
the max surface eng. principal (major) strain 1 can be seen. Finally, the 2D-overlay of the eng. principal
(major) strain 1 can be seen showing fracture occurring at ca. 170 mstrain.
Tensile Test of a 3D-printed Coupon Rectangular Cut-Outs using Istra4D V4.12
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