Ultrasonic testing is used for non-destructive determination of elastic parameters up to orthotropic material behaviour. In contrast to quasi-static experiments, such as tensile, bending or torsion tests, ultrasonic testing is a dynamic measuring method based on time or frequency measurements. The comparatively low amplitudes of the elastic waves only lead to small deflections and thus do not cause any non-linear effects in the material, which means that higher accuracies can be achieved. Three different methods of ultrasonic testing are used at the IAM-WK:
In the pulse-echo method, ultrasonic pulses are passed through the sample to be tested. From the time span required for a pulse to pass through a sample, the propagation speeds of the sound waves can be determined, from which in turn the elastic parameters can be derived.
Ultrasonic Phase Spectroscopy (UPS)
In ultrasonic phase spectroscopy, continuous sound waves are introduced into the sample in a previously defined frequency spectrum. Finally, the propagation speed of the sound waves can be determined by the phase difference between the input and output signal. In contrast to the pulse-echo method, the UPS is particularly suitable for the investigation of strongly sound-attenuating samples.
Resonant Ultrasonic Spectroscopy (RUS)
Resonant ultrasonic spectroscopy allows the determination of the elastic material behavior even on samples in the size of millimeters. The elastic constants are determined via the eigenfrequencies of samples of simple geometry.
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