A holistic approach to the functional requirements of road surfaces regarding noise and rolling resistance
Time: Fri 2020-05-29 14.00
Location: Zoom Webinar -https://kth-se.zoom.us/webinar/register/WN_uBAlg-W_RTKIVOsq7xualw, Du som saknar dator/datorvana kan kontakta email@example.com för information / Use the e-mail address if you need technical assistance, Stockholm (English)
Subject area: Civil and Architectural Engineering, Building Materials
Doctoral student: Tiago Vieira , Byggnadsmaterial, VTI
Opponent: Associate Professor Tony Parry, University of Nottingham, UK
Supervisor: Professor Sigurdur Erlingsson, VTI; Dr Ulf Sandberg, VTI
Increased fuel consumption, increased greenhouse gas emission, diminishing real-estate prices and increased health issues are some of the negative effects on the climate, on the environment and on the society from tyre/road rolling resistance and noise. The first two aspects are affected by energy dissipation in the tyre/pavement contact and are related to rolling resistance. The other two aspects, real-estate property prices and health and comfort issues, are related to noise.
This thesis uses a holistic approach to analyse functional properties of the tyre/road contact interaction. It studies how measures taken for different functional properties may correlate and studies the limits in evaluation of mitigation strategies considering the precision in available measurement methods.
The investigative work included an examination of how reproducible CPX measurements are for evaluating tyre/road noise. Furthermore, the procedure for rubber hardness correction was subjected to a specific evaluation. Noise and rolling resistance measurements were performed on drums and the results were compared to on-road measurements for 50 different tyre models. Additionally, the consistency of rolling resistance measurements on roads was evaluated.
Two mitigation strategies are discussed in this thesis: (i) selection of tyres, and (ii) grinding of road surfaces. For the first strategy, more than 600 CPX and more than 500 rolling resistance measurements were carried out with 50 different tyre models to evaluate potential gain in selecting the best tyres. For the second strategy 8 road sections were ground and the effect of grinding was evaluated with respect to noise and rolling resistance.
The results indicate that when the CPX method is performed correctly, it can consistently evaluate tyre/road noise. Recommendations on how uncertainty in the CPX method can be reduced are included in the thesis. Additionally, recommendations on how the tyre rubber hardness measurements can be improved are also discussed, which is relevant not only for noise measurements but also for rolling resistance measurements.
The selection of tyres is the mitigation strategy that has the largest potential to reduce noise and rolling resistance, yet it can take time to be implemented. On the other hand, surface grinding leads to substantial noise and rolling resistance reductions and can more readily be implemented.
Noise and rolling resistance measurements on roads were compared to measurements on drums and no correlation was found. This indicates that drum results cannot be directly compared to tyre performances on roads.
Values presented on the EU tyre lables were shown to not correlate to on-road measurements; this calls for a re-examination of the tyre labelling procedures. Regarding labelling of road surfaces, results in this thesis indicate that reliable acoustical properties can be obtained with the CPX method in a reproducible way and suggests that acoustical labelling of road surfaces is feasible with a precision of 1 dB.