In this application video, a 2-cam 12 Mpx FlexDIC system is used to measure the crack propagation of a metallic
CT-specimen in Istra4D V4.12.
In the fatigue test, a constant cyclic load at 15 Hz was applied with max load at 5 kN and min load at 500 N. The
DIC system was synchronized using an external TTL clock signal, whereby using the Phase Shifting Method (PSM),
the peak of the sinus oscillatory load was selected at a phase shift of 90° to trigger the cameras. As such, for every
cyclic peak load, one measurement image was acquired.
Analogue data, including force from a load cell and elongation from a CT-extensonometer, were also saved to the
acquired HDF5 step data images. Using the HDF5 data structure, analogue data is stored together with the acquired
step image, and cannot be detached, remove or separated. This advantage prevents data from being lost and being
incorrectly synced/aligned with the respective image.
In the graphical visualization, the 2D-overlay of the engineering principal strain 1 (in mstrain) can be seen that shows
the generation and propagation of the crack tip. Through plotting the temporal analogue values, together with a virtual
line gauge element of the Euclidean length change it can be seen that the virtual gauge elongation matches that of the
CT-extensometer. In making a 2D-overlay of the Y-displacement with RBMR (in um), the crack trajectory can be seen
even before strain is visible. The Rigid Body Motion Removal calculates the average movement of all data points and
removes this amount around the centroid.
In the application scripting modules, the crack propagation module can be used to determine the crack tip trace, location,
length, width, and angle.
Crack Propagation Analysis of a CT-specimen using Istra4D V4.12
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