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Schematic of laser scanning vibrometry of an austenitic steel test sample including an austenitic weld. The sample is 24 mm high.
Snapshot of the ultrasonic wave field in the weld from Fig. 1. The out of plane displacement uz at a given time is displayed as gray values. Note the barely visible gray value variations in the crest of the leading wave front.
Visualization of the 3D data set uz(x, y, t) by drawing cross sections at constant time t = ti, which are called snapshots. For clarity, only six snapshots with a time interval of 1.2 μs are displayed. The displayed scan area is 40 × 22 mm2. The drawn time line is at the scan point xm, ym = 14.5 mm, 4.1 mm. The inset shows the measured signal at that point.
Visualization of the re-slicing of the uz(x, y, t) data set. The tilted plane is orientated in such a way, that it “follows” the longitudinal wave on its path through the specimen.
Grain structure obtained by (a) the conventional metallographic techniques and (b) extracted from the surface skimming longitudinal wave.
(a) The surface skimming longitudinal wave (black solid wavefront lines, propagation vector kl) generates a shear wave (blue dashed wavefront lines, propagation vector kt) and a surface deformation due to traction free boundary conditions; (b) additional displacement contribution of the microstructure is indicated by arrows.
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