Tire characterization for NVH, test methods development

The noise, vibration and harshness (NVH) profile of a vehicle is a key metric by which customers rate vehicle performance. With the advent of the electrification era rolling noise is set to become a dominant source of noise for electric vehicles, due to the phasing out of the internal combustion engine. Interaction between the road and tire contact patch results in excitation of tire natural frequencies. The resulting vibrations are transferred through the wheel centre to the knuckle and subsequently through the vehicle to the cabin. Automotive OEMs rely on experimental and computational tools which can aid in the vibro-acoustic design of their vehicles in order to meet customer demands for quieter vehicles and adhere to traffic noise emission regulations. Siemens Industry Software NV (ex LMS) is a leader in NVH and has developed during the years several concept tire models combined with test setups. The actual tire test, called Fixed – Free, does not capture the effects of some key influencing factors on tire dynamic behaviour, particularly for rolling conditions. The goal of this master thesis is to improve current measurement approaches for tire vibrational behaviour by assess different setups for testing the tire under various boundary conditions and cross-correlate observed behaviour. The tire has been measured in three different test setups, called Free – Free, Static Loaded and Rolling, aiming to obtain an EMA (Experimental Modal Analysis). Modal Analysis is an efficient tool for describing, understanding and modelling any structural behaviour, is the process of determining all the modal parameters, necessary to classified the tire behaviours. The modal analysis is not enough for a complete classification and interpretation of the tire behaviour, so a new kind of approach is used together with the modal analysis: Dispersions Plots. The measurements have been taken with classical accelerometers and with a new instrumentation, the SLDV (Scanning Laser Doppler Vibrometer), with the help of a test rig that represent a quarter of a car. The data analysis shows a correlation between each boundary conditions, a correlation between the sidewall and tread-band of the tire and an evaluation of the measurements with laser in comparison with accelerometers ones.