Fabienne Anfosso-Lédée

Geometric Descriptors of Road Surface Texture in Relation to Tire-Road Noise

The paper deals with the determination of geometric parameters for studying the relationship between tire-road noise and texture of road surfaces. The approach was found to be an alternative to classical spectral analyses and numerical simulations of the tire-road contact. Texture parameters were derived from previous works at the Laboratoire Central des Fonts et Chaussées related to the influence of the microtexture of road surfaces on skid resistance. Use of these parameters was justified by consideration of generation mechanisms of rolling noise. Texture, rolling noise, and absorption measurements were performed on 12 road surfaces. The measuring devices and the test methods produced texture profile analyses, including the spectral and geometric approaches. Geometric parameters were defined. Correlation between the noise and texture spectra showed results similar to those published in previous works. Fair tendencies were found between the global noise level at 90 km/h and the geometric parameters. Unexpected results obtained on the porous asphalt surfaces were partially explained by the attenuation effect, which was quantified by means of existing models. Results from the correlation between the third-octave-band noise levels and the geometric parameters corroborated those of the spectral analyses.

Influence of Road Texture on Tyre/Road Contact in Static Conditions: Numerical and Experimental Comparison

ABSTRACT This paper deals with the influence of road texture on normal pressure distribution for tyre/road contact in statics, within the framework of rolling noise prediction. A contact model is developed in statics where the tyre tread is modelled by an elastic half-space and the road surface by several perfectly rigid asperities. The problem is solved using a Two-scale Iterative Method (TIM) which is fast and efficient. The numerical results give high resolution contact patterns for real road surfaces. Predicted results are compared to contact pressures measured between a slick tyre and several road surfaces. The agreement is fairly acceptable by keeping in mind both the precision of the measurement device and the simplicity of the model. The best correlations are obtained for model surfaces composed of spherical punches and real road surfaces of moderated or high macro-texture. The results are less conclusive for road surfaces of fine macro-texture. The efficiency of the TIM at a tyre/road contact scale is an encouraging first step before introducing dynamical effects.

State-of-the-Art Prediction and Control of Road Traffic Noise in France

Because traffic noise is considered by the French population as the primary environmental nuisance, prediction of road traffic noise and development of efficient noise control techniques is very important. The first step is to analyze the source, the main part of which is due to the contact between tires and the road pavement. Many efforts have been devoted to the assessment of a reliable measurement method, and a classification of road pavements in relation to noise has been established for some years. To abate road traffic noise, special attention has been paid to low-noise pavements. Thus, the modeling of the absorption properties of porous asphalts has been particularly studied in the past 10 years. The second step is to understand the physics of sound propagation outdoors, especially the meteorological effects on the propagation of road traffic noise. Both theoretical and experimental approaches have been undertaken. Finally, the effect of road noise barriers of any shape on the propagation of road noise and their interaction with porous road surfaces have been investigated by using numerical models.

Sound propagation above a porous road surface with extended reaction by boundary element method.

Acoustic impedance of an absorbing interface is easily introduced in boundary element codes provided that a local reaction is assumed. But this assumption is not valid in the case of porous road surface. A two-domain approach was developed for the prediction of sound propagation above a porous layer that takes into account the sound propagation inside the porous material. The porous material is modeled by a homogeneous dissipative fluid medium. An alternative to this time consuming two-domain approach is proposed by using the grazing incidence approximate impedance in the traditional single-domain boundary element method (BEM). It can be checked that this value is numerically consistent with the surface impedance calculated at the interface from the pressure and surface velocity solutions of the two-domain approach. The single-domain BEM introducing this grazing incidence impedance is compared in terms of sound attenuation with analytical solutions and two-domain BEM. The comparison is also performed with the single-domain BEM using the normal incidence impedance, and reveals a much better accuracy for the prediction of sound propagation above a porous interface.

Experimental study of dynamical contact forces for tyre/road noise application

This paper deals with the experimental study of tyre/road contact forces in rolling conditions for tyre/road noise investigation. In situ measurements of contact forces were carried out for a slick tyre rolling on six different road surfaces at rolling speeds between 30 km/h and 50 km/h. Contact stresses were measured at a sampling frequency of 10752 Hz using a single array of pressure sensitive cells placed both along and perpendicular to the rolling direction. The contact areas obtained during rolling were smaller than the one measured in statics. This could be due to an influence of the viscoelastic behavior of the rubber of the tyre tread during rolling. Additionally the root-mean-square of the resultant contact forces at various speeds was in the same order for a given road surface, while their spectra at various speeds were quite different. This could be explained by a spectral influence of the vibration of the tyre during rolling.

Dependence of the contact area on the velocity of a rolling tire

It is known that the eigenfrequencies of a rolling tire depend on the velocity of rotation. We distinguish two causes for the stiffness increase: the frequency dependence of the complex modulus of the materials and the geometrical stiffness. The real part of the Youngs modulus is monotonic according to the frequency. It contributes for an important part to the stiffening. The geometrical stiffness also increases with the rotational velocity. A consequence of these effects is the modification of the size of the contact area for different velocities of a rolling tire. Here we first present experimental results estimating the size of the contact area for a tire in statics and for different rolling velocities. Differences of 20% can be observed. Then the viscoelastic behaviours of the tire materials are presented and experimental results showing the frequency dependence of the complex modulus of the tire constitutive materials are given. Then finite element computations are presented with a real distribution...