Improving Tire Vibration Measurements with VIC-3D

Noise and vibration characteristics are critically important for understanding the mechanical behavior of tires under various loading conditions. Measurements acquired during testing are used to validate finite element computer models to ensure the product meets safety, durability, performance, and longevity requirements. Traditional measurement techniques, such as accelerometers and strain gauges, have been widely used in the industry for decades, but offer minimal information at discrete locations. Full-field 3D non-contact displacement and strain measurements speed up the validation process by providing an abundance of information during a single test which can quickly help engineers visualize how the tire’s surface is behaving. Laser doppler velocimetry systems have been used for such measurements, but this method requires a multitude of points to be scanned on the tire surface.

Digital image correlation (DIC) measurements, on the other hand, are a very effective tool to rapidly obtain full-field vibration measurements with high spatial resolution. The advantages of the DIC method include ease of use, rapid turn-around, simple calibration, and simultaneous acquisition of data on the entire surface, permitting full-field measurement of transient phenomena, as illustrated in this hammer strike example. The VIC-3D Vibration Analysis (FFT) system integrates vibration analysis through a high-performance Fast Fourier Transform (FFT) implementation and an FFT workspace with numerous post-processing and analysis options. Vibration results can also be visualized and animated using the powerful iris graphics engine, and data export compatible with major vibration analysis software packages is available.

In this example, a 24” diameter tire is excited with the tap of a modal hammer at the top of the tire. Images are acquired at 4,000 frames per second using two high-speed cameras mounted on a stereo bar. The images are then post-processed to compute the three-dimensional (U, V, and W) displacement fields. This full-field displacement data is then transformed into the frequency domain using the built-in FFT module. The results are displayed in the workspace graphically and visually with animated 3D contour plots. In-plane and out-of-plane amplitude distributions, strains, and accelerations are shown in 3D or as a 2D overlay on the image and may be animated in 2D or 3D. The results here show the amplitude distribution in all three directions at a frequency of 145.5Hz. Further analysis using the synchronized force data from the modal hammer may be used to compute the frequency response function (FRF). This measurement data is then compared to the computer model predictions to improve the design and overall performance of the tire. With the VIC-3D system, manufacturers save time and money in the R&D phase of development, which enables them to stay ahead of the competition.