As internal combustion engines are replaced by quieter electric motors in ground
vehicles, noise and vibration sources aside from the powertrain have become
relatively more important. This is especially true of tires. Measurement of the
dynamic vibratory characteristics of tires is critical to understanding their
influence on the noise and vibration performance of vehicles, both outside the
vehicle body and inside of it. In this work, the normal modes and operating
deflection shapes of a Yokohama Geolander A/T light truck tire are measured
using traditional modal analysis techniques as well as a non-contact Scanning
Laser Doppler Vibrometry (SLDV) approach. Boundary conditions including free,
fixed, loaded, and rotating are implemented to the tire and investigated.
Rotating conditions are accomplished in a physical chassis dynamometer
environment, with the measured tire mounted on the front axle of a Chevrolet
Silverado 1500 pickup truck. Modes of vibration and associated natural
frequencies that are measured in all four boundary conditions, including
steady-state rotation, are reported and illustrated. Results of the study show
that operating deflection shapes of a rotating light truck tire can be measured
on a chassis dynamometer using SLDV, assuming the tire is undergoing
steady-state rotation, but certain disadvantages in the dynamometer environment
make the measurement procedure challenging. Specific concerns such as tire
rotating speed consistency and sufficient spatial and frequency resolution of
the measurements are delineated in this work. Moreover, practical
recommendations for measurement of rotating tire operating deflection shapes
using a SLDV are included, and a comparison with the Digital Image Correlation
(DIC) method of measurement is presented.
