Identification of natural frequencies of system by means of impact test

Abstract

The calculation of machinery’s natural frequency is a very important
step and must be carried out at the beginning of the design and
fabrication process of any machines or systems. Failing to estimate
natural frequencíe can lead to reducing the longevity or damaging of
machinery. This paper presents the methodology for identification of
natural frequency of a system under flexural vibrtions using the
impact test. The test rig used to identify the natural frequencies
consisted of one shaft and two disks. Acquired signals from
accelerometer and load cell sensors were analyzed and underwent the
Fast Fourier Transform (FFT) algorithm to obtain the transfer
function H1, thus estimated the natural frequencies of the system. In
order to evaluate the accuracy of results, the fucntion’s coherence is
introduced. This methodology is simple, less time consuming and
widely used for the natural frequency calculation with high precision.