A large scale of field-test investigation was conducted in Beijing using Video Drive Recorder (VDR) which
could record image in front of the vehicle. Fifty taxis equipped with VDR were used to collect data in real traffic environments for a whole year and a large volume of naturalistic driving data including crashes and near-crashes was collected. This paper analyzed the pre-event maneuvers of drivers and studied the characteristics of braking operations of Conflict-prone drivers. Then an evaluation method was proposed to rate a driver's accidents avoidance ability, and to evaluate the relationships between driver's brake behaviors and accident rates. The results showed that most evasive maneuvers were within 2s before the most dangerous state. By comparing the near-crashes with crashes recorded by the VDR regarding traffic accidents in Beijing, great similarities were found in accident type and occurrence time between them. According to 100 rear-end near-crashes, if the braking time of drivers were delayed by 0.2s, 17% of near-crashes would have been crashes; and if the braking forces were decreased by 0.1g, 33% of near-crashes would have been crashes.
The cold start performance and ignition characteristics of coconut-oil methyl ester (CME) were investigated
by using a diesel engine. Diesel fuel and CME were mixed and the blended ratio of CME was changed. The tests were conducted at full load and 3000 min-1. Diesel engine could be run stably with any mixing ratio of CME, however the power was slightly reduced with increasing CME mixing ratio. In cold start condition, when the mixing ratio of CME increased, the combustion chamber wall temperature rose quickly and the ignition timing was advanced. Therefore, CME had superior compression ignition characteristics in the cold start.
Numerous aerodynamic designs of high-speed coaches have been made to reduce aerodynamic drag
for lower fuel consumption and to keep the driving stability of the vehicle on a highway. However, the external body shape of a long-distance, high-speed coach manufactured around the world is in a rectangular shaped blunt body. With this conventional body configuration of the bus, it is not easy to have an optimum shape of the bus with the minimum aerodynamic drag. From the previous study, it was found that total aerodynamic drag on a running vehicle is comprised of around 70% in pressure drag by stagnation on the front-side of the vehicle and 30% in induced drag by vortex at the rear-side of it. In this study, a streamlined design concept was incorporated to the front-side of a long-distance model bus to see its effect on the reduction in aerodynamic pressure drag and a general type of RGV (rear guide vane) was applied to see its effect on the reduction in the induced drag at the rear flow field of the model bus. Computational fluid dynamics (CFD) method was incorporated to analyze the variation of aerodynamic effect on the model buses with the change of body configuration.
From the study, it was found that 27.4% of the total drag of the original bus (Model-0) was reduced on the model-3 that is equivalent to 17.3kW of an engine brake power at 120km/h in speed. The annual economical effect is the reductions in about 14,610 liters of fuel and 41.2 tons of CO2 per year by each car at the assumed operating condition.
High strain rate properties of sheet steel largely depend on its strength level and strengthening mechanisms. The strain rate sensitivity of flow stress has a close relation with the hardness of a softer phase, which indicates superior strain rate sensitivity of multi-phase steels such as DP and TRIP steels. Simple-shear tests have revealed an increase of the flow stress with strain even for ultra high strength steel at large strains. Based on these experimental evidences and physical understandings, an appropriate constitutive model for crash simulation is proposed and discussed.
State-of-the-art vehicles already show an aerodynamically well improved bodywork with high-level
efficiency. To further improve the aerodynamic drag, one potential area is the interaction between the underhood and the external flow.
This study presents an experimental and numerical investigation of the interference effects of the cooling-air flow with the external-aerodynamics. Extensive measurements, like forces and total-pressure were accomplished. A simple dependency between drag and cooling-air mass-flow is derived, which will help for daily wind-tunnel work.
The rubber O-rings used in high-pressure hydrogen environment sometimes suffer from the decrease in
durability due to decompression failure. A high-pressure durability tester, which enables rubber O-rings to expose repeatedly high-pressure hydrogen gas at arbitrary test conditions, was employed, and then sensitive factors for the durability of the O-rings were evaluated by using a L18 orthogonal array. Of lower-limit pressure, upper-limit pressure, material, temperature, O-ring filling ratio, holding time at lower limit, holding time at upper limit, and decompression time, it was clarified that the material, temperature, O-ring filling ratio, and decompression time were sensitive factors.
Strength and work-hardening in steels are discussed from the viewpoint of heterogeneous deformation. In-situ neutron diffraction studies made it clear that misfit strains between grains accompanied grain-scaled internal stresses (intergranular stress). In a dual phase steel, the intergranular stress was superposed on the phase stress. These results show good agreement with the predictions of a simple dual-phase material model: the strong martensite phase yields higher stress than the macro-yield stress, resulting in high strengthening of (ferrite + martensite) dual phase steels. Both long-range internal stress and short-range ones such as forest dislocation hardening may cause resistance to dislocation motion in the steels. Therefore, work-hardening takes place more effectively with higher internal stress and larger volume fraction.
Walking aids are vehicles that need to carry a major part of the user's weight and to run on roads. Therefore,
automotive engineering was applied in this study to improve the walking aid design. The walking aid developed can turn in a small space such as in an elevator, ride over gaps such as curbs, and keep straight trajectories on rough and slanted surfaces with minimum user effort. The core part of this design lies in the adoption of a multi-functional swing-arm suspension for the front caster wheels and direct yaw-moment control by the rear-wheel motor drives.
Future downsizing for gasoline engines will lead to higher boost ratio and specific torque than realized with todays engines. In the present paper, the vehicle integration of a 2-stage-turbocharging system into a middle class vehicle is discussed, starting with the adaptation of the combustion system to high boosting ratio by means of CFD supported Charge-Motion-Design-Process. Furthermore, the layout of the control concept had been supported by 1D-simulation of the overall engine/vehicle-system. Results from this work will be presented and compared to vehicle measurement data, leading to an assessment of optimization potential regarding drivability and discussing the sensor and actuator concept.
Air bubbles in engine oil cause the serious issues, while high flow rate of the oil is circulated in resent
engines lubrication system. In this study, the authors developed the bubble measurement technique based on image processing and analysis. This technique enables bubble diameter distribution and oil aeration rate to be measured without oil sampling. This measurement technique was applied to the operating engine and the bubble behavior in each lubrication passage was observed.