2. Operation characteristics and measuring method
The vibration generated by rivet tools is a series of periodic
impulsive accelerations as shown in Fig. 2. Both signals
from the rivet hammer and the bucking bar are sharp impulsive
oscillations and the duration was less than 0.4 s in a 0.5 s time
record window.
These highly impulsive and short-duration vibration signals
present quite a challenge for proper data acquisition and spectral
analysis. The signal diminished before the end of time block
window, which generates large leakage errors, are not acceptable
for an accurate measurement. A post-transient window should be
used to reduce the leakage to the minimum as shown in Fig. 3.
ISO Standard 5349 (1986) requires that the measured acceleration
be weighted and analyzed in a one-third octave spectrum
from 0 to 1250 Hz as given in the following equation: