Gabriel Anghelache

Measurement of stress distributions in truck tyre contact patch in real rolling conditions

Stress distributions on three orthogonal directions have been measured across the contact patch of truck tyres using the complex measuring system that contains a transducer assembly with 30 sensing elements placed in the road surface. The measurements have been performed in straight line, in real rolling conditions. Software applications for calibration, data acquisition, and data processing were developed. The influence of changes in inflation pressure and rolling speed on the shapes and sizes of truck tyre contact patch has been shown. The shapes and magnitudes of normal, longitudinal, and lateral stress distributions, measured at low speed, have been presented and commented. The effect of wheel toe-in and camber on the stress distribution results was observed. The paper highlights the impact of the longitudinal tread ribs on the shear stress distributions. The ratios of stress distributions in the truck tyre contact patch have been computed and discussed.

Investigation of the influence of vertical force on the contact between truck tyre and road using finite element analyses

In the modern context of automobile integration with the emerging technologies of the interconnected society, the interaction between tyre and road is an element of major importance for automobile safety systems such as the intelligent tyres, as well as for passenger comfort, fuel economy, environmental protection, infrastructure and vehicle durability. The tyre-road contact generates the distribution of forces exerted on each unit area in the contact patch, therefore the distribution of contact stresses on three orthogonal directions. The numerical investigation of stresses distribution in the contact patch requires the development of finite element models capable of accurately describing the interaction between tyre and rolling surface. The complex finite element model developed for the 11R22.5 truck tyre has been used for investigating the influence of vertical force on the distributions of contact stresses. In addition to these contributions, the paper presents aspects related to the simulation of truck tyre radial stiffness. The influence of tyre rolling has not been taken into consideration, as the purpose of the current research is the investigation of tyre-road contact in stationary conditions.

Investigation of a Mechanism Through a Transient Thermal Analysis and an Equivalent Steady-State Thermal Analysis

The thermal analysis of a rotary engine mechanism requires taking into consideration the transfer of heat from the combustion gas to the engine parts, which include rotating parts and fixed parts, as well as the transfer of heat to the environment. During an engine mechanism rotation, the conditions of convective heat transfer are variable, and the surfaces of fixed parts exposed to combustion gas are continuously changing. In this case, the transient thermal analysis using the finite elements method is very complex because of the permanent modification of surfaces covered with combustion gas, as a consequence of mechanism rotation. Therefore, in the current paper, an equivalent model for steady-state thermal analysis is developed, so that the same results are obtained as in the long transient thermal analysis, but with significantly smaller requirements of time and computational resources. The transient thermal analysis performed for a large number of rotations, which provides the stationary thermal conditions of mechanism parts, is compared with the equivalent steady-state thermal analysis performed using the equivalent film coefficients and the equivalent convection temperatures. The distributions of fixed part temperature and heat flux obtained from the steady-state thermal analysis are compared to those obtained from the transient thermal analysis, and very good similarities are ascertained. In conclusion, the equivalent steady-state thermal analysis provides similar results, compared with the transient thermal analysis, but with significantly lower computational effort.

Measurement of Fuel Consumption for an Off-road Vehicle With Conventional and Hybrid Powertrain

The hybrid powertrain of an off-road vehicle allows reducing fuel consumption and exhaust emissions. For a small off-road vehicle, the development of a prototype hybrid powertrain has been achieved. One of the possibilities to quantify the efficiency of hybridization consists of comparing the fuel consumption for the vehicle with conventional powertrain and for the same vehicle with prototype hybrid transmission. The comparison has been made through experimental investigation of fuel consumption. Fuel consumption measurements have been performed using portable equipment with high-precision volumetric flowmeters. A data acquisition system with specially developed LabVIEW applications has been mounted on-board the vehicle for real-time measurement of fuel flow. During road rolling, the measuring system has also allowed real-time monitoring and adjustment of vehicle speed according to the NEDC (New European Drive Cycle). Vehicle speed measurement in road conditions has been performed using an optical speed transducer. For the vehicle with conventional powertrain, the measurement of fuel consumption has been performed both in real road conditions and on the chassis dynamometer, at variable speed according to the urban drive cycle NEDC. For the vehicle with hybrid powertrain, the measurement of fuel consumption has been performed on the chassis dynamometer, at variable speed according to the urban drive cycle NEDC. The hybrid powertrain measurement results have been compared to those obtained for the vehicle with conventional powertrain, and a decrease of fuel consumption has been ascertained.