I am interested in knowing if there is any method to measure the eigenfrequency of very small object of size 5mm x 5mm x 3mm. Material is an elastomer. The problem associated with this is material mass is 0.3grams but sensor(accelerometer) mass is 4 grams. so sensor mass affects the measuring frequency and eigen frequency of the material. I am in need of a solution(Experimental Method) for finding eigen frequency of such a small object with very low density or mass.
Thank you Solbrig for your suggestion. And the material is mounted on a piezoelectric shaker and is excited upti 15kHz. Now mounting is also a problem for my work. The material will be in compression.
Maybe using an inderect meassure. If your sample is attached to another well known system you can infer the phisical properties of the sample by inspecting the modifications it leads to the augmented system. This can be done easily if you made the strong assumption that the sample can be modelled as a single degree of freedom linear system.
use non contact sensors like laser vibrometer
the mass of your system is very small (0.3g) hence the environment would be having an effect on your measurements ......try to perform your experiment in a noise proof environment
find a way tp excite your system .........traditional vibrational shakers having electro or hydrodynamic would not be suitable because their inherent nonlinearities would effect your measurements given small nature of your speciment
it may be a good idea to look into designing your own shaker system using Voice Coil Motors for example
Hi, Mount your specimen on shaker and You can find the resonant frequency by sweeping the excitation frequency given to shaker and measure any data like strain, displacement, velocity, voltage (piezo material). But if beam is an elastomer, theoretical and experimental values matches pretty well. No need to measure.
Hi
I am acoustician so I would use a microphone provided you can vibrate the object and provided you only want frequency.
In the so called nearlfield, i.e. very close to the object, vibration and pressure is the same albeit not of same amplitude as the decay in the nearfield is 55 dB/distance doubling.
Vibration can be inferred using magnetic field is the object is magnetic or sprayed with metal paint.
Use a low cost electret microphone. You can get a bunch of them for no money at all.
http://www.ebay.de/itm/Panasonic-microphone-inserts-WM-62PCX-6x3mm-5-Stuck-/310704465283?hash=item48576de583
http://www.ebay.de/itm/100-x-Panasonic-Mikrofonkapseln-Panasonic-Condenser-Microphon-Lager-B141-/171139615312?hash=item27d8b74a50
As a comment. Lasers are nice. However, light carries momentum (use a photoflash on a gong-gong & you will hear a gong when firing the flash) and may or may not affect small size objects.
/Claes
Many Thanx Dr. Fredö. Always I find your answers close my research, I will contact you personally through mail.
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