In this application video, a 4-cam 5 Mpx MulticamDIC system is used to measure the thickness
change, strain Y, and strain XY of a 3D-printed Titanium Coupon in a tensile test using Istra4D V4.12.
The MulticamDIC system uses a double-sided setup, whereby cameras 1 & 2 view the frontside of
the specimen and cameras 3 & 4 view the backside of the specimen. Using a double-sided calibration
target, the projection of cameras together are calibrated in one coordinate system, as such, no image
stitching is used. This also allows adjacent points on either face sides to be accurately determined.
In the correlation evaluation, an Object Alignment Parameterization (OAP) is used, which aligns the
facets/subsets to an object model, instead of using a reference camera perspective. This allows the
correlation of complex and/or large objects to be undertaken, additionally, it also reduces the measurement
uncertainty (MU) of the measurement – since there is no perspective shape distortion of the facet/subset alignment.
In the graphical visualization, a 2D-overlay of the total displacement with rigid body motion removed
(RBMR) can be seen. Using a virtual line gauge marker, a temporal plot of Euclidean length change
(mm) & absolute load (N) shows the coupon elongated by ca. 2 mm and the sample fractured around
23 kN. Using the 3D-visualization grid model, the change in contour (shape) of the sample during the
test can be seen, whereby green indicates the reference state and red shows the measured step. In the
measured step, the lattice structure of the coupon is also clearly visible. A virtual point gauge is also used
to measure the contour thickness, as can be seen, a corresponding virtual point gauge marker is placed on
the adjacent side. (This is only possible by using a double-sided calibration target and biplanar OAP) It is clear
that the thickness of the coupon reduced by ca. 200 um from a starting thickness of 5.2 mm. A 2D-overlay of
the engineering Y-tangential strain and shear strain XY (in mstrain), with Y-defined in the direction of load
application, can be seen showing the strain structure in the titanium lattice. At step 486, a peak 300 mstrain
concentration is formed around the centre of the coupon, where fracture eventually occurs. The engineering
principal strain 3 is also presented in the 2D-overlay, which represents the contraction strain deformation of
the sample. (This 3D-strain definition is only possible by using a double-sided calibration target and biplanar OAP).
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