Resonance analysis
Construction units and components, which are exposed to dynamic forces within their intended use, are usually submitted to extensive tests before starting the series production . For this purpose special testing machines, which simulate a dynamic strain similar to the real operating one, are used. In the vehicle industry for example so-called hydraulic pulsators are used to shake the entire vehicle by means of force application into the wheels, producing oscillations, which correspond to those resulting from running on a respective road surfacing. Beyond that electro-dynamic swinging tables are frequently used to apply a defined testing vibration program to single components. Usually a characteristic frequency band is run and the reaction of the test specimen is recorded by means of acceleration sensors. In numerous cases not the acceleration signals are of interest, but the displacement carried out by a test specimen.
In practice determining the displacement from the measured values of the acceleration through a double integration leads frequently - if at all possible - to unsatisfactory results. LaserCam permits measuring the displacement directly with the necessary precision.
For this purpose a lase diode is mounted to the specimen. The laser directs its beam towards the target of LaserCam. If only pure torsional vibrations are considered, a mirror instead of the laser diode can be attached to the specimen.
Animation (1) shows deflections of a specimen caused by torsional vibrations, which was recorded with LaserCam_highspeed* at a rate of 1000 cycles per second. Two subsequent points of the track are 1 millisecond apart. The distance bewteen the points of the track can be computed with LaserCam. From the recorded information both the displacement and the acceleration can be determnined.
Alternatively (2) the complete shape formed during an oscillation period can be recorded using LaserCam_osc*. By this measuring princpile a periodic oscillation is assumed. On the other hand there are almost no limits concerning occurring velocites and accelerations. If occurring accelerations and velocities are also to be measured, a frequency modulated laser can be used.
(*LaserCam_highspeed and LaserCam_osc specifications on request)
