In this application video, a 2-cam (16 Mpx) MSpeedDIC system is used to measure the impact (specifically
displacement & strain) of a metal ball being dropped on an aluminium honeycomb component.
In the measurement, the real-time speckle pattern quality evaluator indicates the optimal facet/subset size
for the correlation evaluation. Then after, the projection calibration is performed by rotating the stereo rig
(whilst keeping the cameras and lenses fixed) away from the specimen. The 10mm double-sided calibration
target is automatically recognized in the Istra4D V4.11 software via it’s QR-code, which entails information
about the grid spacing, std. tolerances, and front/rear properties (such as thickness, which is used for
double-sided biplanar setups). The projection parameters are computed live with feedback. Users can easily
manoeuvre & orientate the target based on the visual indicators.
A ringbuffer recording is performed at 500 Hz capturing a total of 3500 frames/steps. The pre/post trigger was
set at the end of the recording, as such, the ball is dropped, then the trigger is initiated saving all the events
that occurred beforehand.
From using the measured series & projection calibration, the correlation evaluation is then performed.
The correlation evaluation is performed with live feedback of the selected visualization.
From the graphical visualization, a 3D-visualization model shows the total-displacement (um). The shockwave
from the impact can be instantly seen. It seems that after impact a dent at the point of impact has been created.
Through visualization of the 2D-overly of the total displacement (mm) with rigid body motion removed (RBMR),
it is clear that the dent was more than 150 um of permanent deformation. Through measuring the engineering
principal strain 1 around the point of impact, it is clear exactly when the impact/shock took place and the result
of the impact as permanent deformation/strain in the order of 8 mstrain. It is also clear that the panel was able to
withstand most of the impact/shock, which can be seen from the partial recovering of maximum strain at impact.
