International audienceA method is presented here for modeling and predicting the rolling and yaw behavior of an aircraft tire which is subjected to a strong inflation pressure and a concentrated load on the axle, in contact with a flat, rigid surface. Finite element methods were used to model and simulate the aircraft tire/ground interactions. The incompressibility of the material, the large transformations and the unilateral contact with Coulomb friction law were all taken into account. Imaging methods were used to examine the complex structure of the tire cross-section. Comparisons are made between the data obtained with the model, the experimental data and those provided by the manufacturer. The tire response predictions were found to depend considerably on the material and the geometrical characteristics of the tire
This paper presents a numerical simulation of an aircraft tire in contact with a rough surface using a variable friction coefficient dependent on temperature and contact pressure. A sliding facility was used in order to evaluate this dependence of the friction coefficient. The temperature diffusion throughout the tire cross-section was measured by means of thermocouples. Both frictional heating and temperature diffusion were compared to numerical two-and three-dimensional simulations. An adequate temperature prediction could be obtained. In future simulations, wear should be taken into account in order to have a more accurate simulation especially in the case of high pressures and slipping velocities. A 3D finite element model for a rolling tire at a velocity of 37.79 knots (19.44 m/s) and in a cornering phase was investigated using a variable friction coefficient dependent on temperature and pressure. The numerical simulation tended to predict the temperature of the tire tread after a few seconds of rolling in skidding position, the temperature of the contact zone increases to 140 • C. Further investigations must be carried out in order to obtain the evolution of the temperature observed experimentally. The authors would like to point out that for confidentiality reasons, certain numerical data could not be revealed.
Influence of roughness on mechanical strength of direct bonded silica and Zerodur® glasses Direct bonding is of particular interest for optical system manufacturing for spatial application. This process requires very precise physical and chemical preparations of surface, especially roughness controls. Thus, this paper proposes to understand and discuss the roughness influence on mechanical strength and bonding energy of an elementary mechanical structure after a room temperature bonding and an annealing at optimal temperature. First, surfaces are characterised and roughness is measured. At the same time, the performances of fused silica and Zerodur® glasses are compared. Then interface properties are measured using double shear and wedge tests. At the end of the paper, a discussion, based on literature models, is proposed to explain the existence of an optimum of roughness put in evidence in experimental results.
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