Rolling Tire Diagnostic Experiments for Identifying Incipient Bead Damage Using Time, Frequency, and Phase Plane Analysis

Automotive tires must meet the US DOT/NHTSA durability regulations set forth in FMVSS139 for vehicles of less than 10,000 lbs GVW. Offline inspection during fatigue endurance testing is time consuming, costly, and involves variability in durability ratings; therefore, a means for determining the health of rolling tires online during testing is desired.

This paper investigates the use of passive time, frequency, and phase-plane methods for detecting structural changes in rolling tires. Operational data were taken on a chassis roller where the left front tire of a vehicle was tested under various loads. Acceleration measurements were recorded on the spindle arm and the data were synchronized with the rotations of the wheel and roller to analyze cycle-to-cycle variability. Modal measurements were also made at the end of each operational test; this data provided some indication of structural changes in the tire. Restoring forces generated for the low frequency content of the operating data were inconclusive. Transient wavelets applied to the operational data were more indicative of small-scale tire damage than were harmonic wavelets.