Automotive NVH (Noise, Vibration and Harshness) is one of the most critical points for customers' comfort evaluation. Noise inside the cabin has recently received special attention due to the continuous development and diffusion of E-cars. Different noise sources have been identified: the engine, suspension, tire, powertrain, brake system, etc. The biggest contributor has been recognized in the tire noise. Particularly, at mid-speed driving, when the engine and the powertrain work at minimum noise, the tire noise is the most critical factor for NVH that has to be taken into account.
At the state of art, the identification and characterization of Noise and Vibration sources rely on pointwise sensors (microphones, accelerometers, strain gauges). Optical methods such as Digital Image Correlation (DIC) and Laser Doppler Vibrometer (LDV) have recently received special attention in NVH field because they can be used to obtain full-field measurements. Moreover, these same techniques could also be used to characterize the tire behavior in operating conditions, which would be practically impossible to derive with standard techniques.
In this paper we will demonstrate how non-contact full-field measurement techniques can be used to reliably and robustly characterize the tire behavior up to 300 Hz, focusing on static conditions. Experimental modal analysis will be applied with the tire in both Free-free and statically preloaded boundary conditions, using both DIC and LDV, to extract the modal characteristic of the structure. The extracted natural frequencies, damping ratios and full-field modes shapers will be used on one side to improve the accuracy of tire models (either by deriving FRF based models or updating FE ones) and will be used as a reference for future investigation on the characterization of the tire behavior in rotating conditions.