A MECHANICAL MODEL FOR THE PREDICTION OF THE TIRE/ROAD FRICTION
The viscoelastic deformation of tire rubber by road surface asperities was modeled by the rolling contact between a Kelvin solid and a surface motif, which is the part of surface profiles between two peaks. Stress and strain calculations showed that contact losses might occur locally, depending on the rolling speed, the viscoelastic properties of the Kelvin solid and the geometry of the motif. Mean vertical and horizontal forces were calculated, from which a coefficient of friction was derived. The model was successfully coupled with a profile analysis method to predict tire/road friction at low speed from road surface microtexture. The contribution of various texture scales to friction was emphasized. For the covering abstract see ITRD E118503.
CHARACTERIZATION OF MICROTEXTURE RELATED TO WET ROAD/TIRE FRICTION
This paper deals with the determination of roughness parameters which could be used to study the influence of microtexture on wet road/tire friction. Two types of surface were studied: laboratory-made GRAP specimens, which surface is composed of similar size coarse aggregates, and road specimens taken from test sites. Friction and surface geometry were measured after polishing. GRAP specimens were polished in laboratory using a projection method. Road surfaces were polished by traffic. Friction was measured by means of SRT pendulum. Microtexture was measured by a non-contact method using auto focus laser sensor and also by a contact method using stylus sensor. Relevance of roughness parameters was evaluated from their correlation with friction. Research was focused on shape parameters. Criteria were defined to select surface peaks, which are likely to touch the tire rubber, and valleys. Fair correlations were found with two parameters: one characterizing surface relief, defined from the curve connecting profile peaks, and one related to peak contact pressure, defined from the curve connecting profile peaks and valleys. The influence of the number of indenters on friction was found to be significant also. A predictive equation was derived empirically, which gives reasonable friction values compared with measured values. Suitability of measurement techniques to FRAP and road specimens is discussed. The influence of profile type on results was also dealt with. Finally, comparisons between results obtained from this study and those from previous works were made.
A New Vacuum Pressure Infiltration CFRP Method and Preparation Experimental Study of Composite
In order to prepare a carbon-fiber-reinforced polymer composite (CFRP) with ideal microstructure and properties, a new vacuum pressure infiltration CFRP method is proposed based on an analysis of existing CFRP preparation process methods. Research on composite material preparation systems was carried out by using this new method principle. The system mainly includes a fiber pre-forming module, a vacuum heating infiltration module, a hot-press curing molding module, and a data acquisition control module. Under the conditions of natural curing at 0 MPa + 6 h + 25 °C, vacuum heating curing at –0.05 MPa + 30 min + 80 °C, and hot-press curing at 0.7 MPa + 5 min + 50 °C, a two-dimensional (2D) CFRP with excellent microstructure and properties was successfully prepared. Observing the microstructure of the prepared composite material, it can be found that the inside of the composite material was sufficiently and uniformly infiltrated, and common preparation defects such as holes and delamination were effectively controlled. Through the performance test, the bending strength of the material reached 790 MPa.