Testing Procedure
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Figure 21: Testing for longitudinal resonance frequency
Place the accelerometer on the required location (contact point at
the center of the face), intimate contact between accelerometer and
specimen is required. For the ends of the specimens to be free to
vibrate in a longitudinal direction, it is essential that minimum
restraint is imposed on the ends. The accelerometer is free to
move in compliant mountings and it is necessary only to move the
accelerometer support along the rails until the contact tip of the
accelerometer just make contact with the center of the ends of the
specimen. A coupling agent may be used to assure good contact
between them (a coupling agent may be required to assure intimate
contact). The support may now be locked by using the knurled
clamping screws. The accelerometer may also be placed on the
surface of the specimen without using its support. It could be
attached on the surface of the specimen by using wax and pressing
it against the surface (as described in the
“Review Menu” chapter).
By pressing the right arrow key, the message “Run enable is On”
will appear on the screen. Then tap the specimen using a
hardened steel ball, causing the instrument to trigger and a signal
will appear in the screen. Caution should be taken to apply just one
solid impact; otherwise the test should be performed again because
the results are not going to be consistent. It is recommended to
repeat the test three times to check the consistency of the results.
