Acoustic resonance analysis
The acoustic resonance analysis , commonly referred to as "sound check", one of the non-destructive testing methods. It evaluates the spectrum of resonance frequencies that arise when the workpiece is set into vibration by an impulsive excitation such as an impact . In the body propagate sound waves from ( longitudinal waves , shear waves ) and the body swings over time in certain characteristic shapes and frequencies, the so-called natural natural or resonance vibration - short resonances.
From the resonance frequencies, specific acoustic parameters can be calculated for the respective workpiece and thus quality characteristics such as “OK”, “cracked”, “material and structural defects” can be assigned. The assignment is made by comparing the measured characteristic values with the values of comparison objects with known properties. The characteristic values depend on the geometry, the material and the internal structure of the test object.
Mechanical vibrations in a body ( structure-borne sound ) cause the surrounding air to vibrate ( air- borne sound ). These vibrations can be measured with appropriate sensors; in the air with a microphone, on a body with an accelerometer or a laser vibrometer. At the same time, many modes of vibration spread in the body, which are characterized by elasticity, shape, material and structure. They represent the mechanical properties of the body. Influences such as B. a crack, a different geometry or a change in material affect the resonance frequencies. Acoustic material testing makes use of precisely these effects.
literature
- Ingolf Hertlin: Acoustic resonance analysis . 1st edition. Castell Wuppertal, 2003, ISBN 3-934255-06-X .
- Acoustic resonance methods - DGZfP guideline US6 . 2009.