Quantifying the Non-stationarity of Vehicle Vibrations with the Run Test

This paper investigates the applicability of the run test as a tool to quantify the statistical non‐stationarity of road vehicle vibrations. The run test was applied to the moving root‐mean‐square (RMS) time history of a number of vibration records measured from a variety of vehicle types, routes and vehicle speeds. The paper discusses the limitations associated with calculating the moving RMS of random signals especially with respect to the window width. When applied to the set of vibration records (with segments of inactivity removed), the run test indicates that every record is non‐stationary. A run ratio parameter was introduced to quantify the level of non‐stationarity, which shows that the result is sometimes dependent on the RMS window width. Further analysis correlating the run test results with the statistical distribution or the RMS indicates that the run ratio parameter has some merit in quantifying the level of non‐stationarity in road vehicle vibrations. Copyright © 2013 John Wiley & Sons, Ltd. The results of run tests applied to the RMS time histories of vibration data measured from a variety of vehicles travelling on various roads at arbitrary speeds show conclusively that every record is non‐stationary. This is significant when simulating vibrations for evaluating the robustness of products or the effectiveness of protective packaging systems. A run ratio parameter was introduced to quantify the level of non‐stationarity, which shows that the result is sometimes dependent on the RMS window width.