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891.
Although automobile crash test data have a comparatively large variation because of the complexity of the tests, only a limited number of crash tests are usually conducted due to monetary and time limitations. Thus, it is necessary to control input variables that cause the variation in test data to obtain consistent crash test results and to correctly assess the safety performance of an automobile under development. In this study, a MADYMO model was validated deterministically to yield the head, chest, pelvis deceleration pulses of anthropomorphic test devices and the belt load pulses similar to those from actual tests, and it was also validated stochastically to yield means and standard deviations of the head and chest injury numbers, i.e., HIC 15 and 3 msec clip similar to those from actual tests. A stochastic analysis was conducted using the validated MADYMO model to calculate the sensitivity of the standard deviations of the injury numbers to the standard deviations of influential input variables to determine the most influential input variable that makes the largest contribution to the variation in the injury numbers. Moreover, the Taguchi approach was used to determine the optimal values of the influential input variables to improve safety performance.  相似文献   
892.
Driving demands significant psychomotor attention and requires even more when drivers are engaged in secondary tasks that increase cognitive workload and divert attention. It is well established that age influences driving risk. Less is known about how culture impacts changes in attention. We conducted parallel driving simulations in the US and Korea to measure the extent to which age and culture influence dual-task performance. There were 135 participants divided into two groups: a younger group aged 20∼29, and an older group aged 60∼69. Whereas some differences by culture appeared in absolute control measures, the younger participants showed similar mean velocity and compensatory patterns associated with increased cognitive load in the urban setting; however, the results from the older samples were less similar.  相似文献   
893.
Vehicle systems such as the steering, brakes and suspension greatly influence vehicle safety. Therefore, these systems must be inspected to guarantee that they are functioning correctly and to certify that the vehicle is functioning at a satisfactory safety level. In disc brakes, warping is one of the principal reasons for vibrations and noise, and it contributes to diminished brake efficiency. Currently, the International Motor Vehicle Inspection Committee (CITA) demands disc brake warping inspections occur during periodic motor vehicle inspections (PMVIs); however, the procedure to carry out this inspection is not well defined. In this investigation, the warping phenomenon has been analyzed, and a new inspection procedure is proposed.  相似文献   
894.
Hydraulically damped rubber mount (HDM) can effectively attenuate vibrations transmitted between an automotive powertrain and body/chassis and reduce interior noise in the car compartment. Predicting the dynamic characteristics of a HDM faces challenges due to fluid-structure interactions between the rubber spring and fluid in the chambers, nonlinear material properties of the rubber parts and turbulent flow in the chambers and fluid track linking chambers. In this paper, an experimental analysis and hydrostatic finite element (FE) modeling technique are integrated in a numerical simulation approach to modeling the dynamic characteristics of a HDM with a lumped-parameter HDM model. The dynamic characteristics of a typical HDM with a fixed decoupler are predicted and compared with experimental results, which verify the effectiveness of the proposed approach. Moreover, a parametric effect analysis is performed to demonstrate parameter influence on dynamic characteristic, which provides a concise design guideline for the parameter adjustments necessary for a HDM to meet the vibration isolation requirements of a powertrain mount system.  相似文献   
895.
In this paper, in order to save time and cost for the fatigue design and to develop the optimum approaches for accelerated life prediction of the fillet gas welded joints, the (Δσ)R − Nf relationship was obtained from actual fatigue test data, including welding residual stress. Based on these results, the (Δσa)R − (Nf)ALP relationship derived from the method of statistical probability analysis was compared with the actual fatigue test data. From the result, the optimum statistical distribution for the accelerated life prediction was analyzed to be the lognormal distribution for the fillet-type, gas-welded joint. The mean accuracy of the accelerated life prediction was assessed to be 85∼95% of the actual test life at the 95% reliability level and ±15% standard deviation. Therefore, it is expected that the accelerated life prediction will provide a useful method for determining the criterion for fatigue design and for predicting a specific target life.  相似文献   
896.
This paper presents a design technique to optimize the shape of a vehicle bumper beam that satisfies both the safety requirements for a front rigid-wall impact and the regulations protecting pedestrians from lower leg injuries caused by bumper impacts. An intermediate response surface modeling (IRSM) technique was introduced to approximate the non-linear force-displacement curves obtained from the front impact analysis of a vehicle bumper. The accuracy of the IRSM model was tested by comparing its results with those of the non-linear finite element analysis. The maximum displacement error between the two models did not exceed 3%. Using pedestrian impact analyses based on the experimental arrangement of the Plackett-Burman design, the approximate functions describing the response values acting on the lower legs were calculated. The shape of the bumper beam was optimized by integrating the IRSM with the force-displacement model and the approximate functions on lower leg impact. The optimization results satisfied safety regulations on the maximum allowable displacement of the vehicle bumper, and also the regulations protecting pedestrians from lower leg injuries caused by bumper impacts.  相似文献   
897.
This research investigated the spray and combustion characteristics of compressed ignition type LPG fuel when a cetane number enhancing additive was applied to a constant volume chamber. Because LPG has a lower cetane number, DTBP and alpha olefin were added to the LPG (100% butane) to enhance the cetane number and viscosity. By adding the cetane enhancer, stable combustion over the wide range of the ambient conditions was possible as well. According to the blending rates of DTBP and alpha olefin, various proportions of LPG blended fuels were obtained. In a constant volume chamber, a high speed digital camera was also employed to visualize the combustion characteristics of LPG fuel. The combustion pressures and heat-release rates of the LPG blends were also compared at various ambient pressures. As the results of measurements of exhaust emissions, CO and HC were reduced considerably, but CO2 was increased by blending LPG with DTBP and alpha olefin.  相似文献   
898.
The particle size distribution and particle number (PN) concentration emitted by internal combustion engine are a subject of significant environmental concern because of their adverse health effects and environmental impact. This subject has recently attracted the attention of the Particle Measurement Programme (PMP). In 2007, the UN-ECE GRPE PMP proposed a new method to measure particle emissions in the diluted exhaust of automotive engines and a regulation limit (<6.0×1011 #/km, number of particles). The specific PN regulation of spark-ignited combustion engine will be regulated starting on September 1, 2014 (EURO 6). In this study, three types of LPG supply systems (a mixer system and a multi-point injection system with gas-phase or liquid-phase LPG fuel) were used for a comparison of the particulate emission characteristics, including the nano-sized particle number density. Each of the three LPG vehicles with various LPG injection systems contained a multi-cylinder engine with same displacement volumes of 2,000 cm3 and a three-way catalytic converter. The test fuel that was used in this study for the spark-ignited combustion engine was n-butane basis LPG fuel, which is primarily used for taxi vehicles in Korea. The characteristics of nano-particle size distribution and number concentration of particle sizes ranging from 20 to 1,000 nm (aerodynamic diameter) that were emitted from the three LPG vehicles with various LPG supply systems were investigated by using a condensation particle counter (CPC), which is recommended by the PMP under both the NEDC and FTP-75 test modes on a chassis dynamometer. The experimental results indicate that the PN emission characteristics that were obtained by the CPC system using the PMP procedure are sufficiently reliable compared to other regulated emissions. Additionally, the sources of PN emissions in ascending order of magnitude are as follows: mixer type, gas-phase LPG injection (LPGi) and liquid-phase LPG injection (LPLi) passenger vehicles. The liquid-phase LPG injection system produced relatively large particle sizes and number concentrations compared to the gaseous system, regardless of the vehicle driving cycle. This phenomenon can be explained by unburned micro-fuel droplets that were generated due to a relatively short homogeneous fuel-air mixture duration in the engine intake manifold. Also the particle number emissions from the LPG vehicle were influenced by the vehicle driving cycle.  相似文献   
899.
In this study, a new concept for a power delivery system is developed. Power Shift Drive (PSD) Axle vehicle modeling and dynamic movement analysis are performed via simulation. The dynamic vehicle model is constructed from data obtained from the derived equation, considering the specific characteristics of each part. The model is composed of a torque converter, a gear box, a differential, hub reduction and an engine, which is the power source of the 1st forward and reverse PSD-Axle. By unifying the mathematical equations for each component, a mathematical model of the 1st forward gear is derived. The system dynamic model is created using MATLAB/Simulink based on the mathematical model. Simulation is carried out using Simulink to estimate the dynamic behavior of the PSD-Axle. In addition, the dynamo test result is used to verify the model. Finally, a successful model is created. This study will be used to establish the basic conceptual design for the PSD-Axle multi-gear system.  相似文献   
900.
Vehicle safety has become the most important issue in automobile design. However, all efforts to improve safety devices focus on enhancing safety features for occupants. Notably, pedestrians are the second largest category of motor vehicle deaths, after occupants, and account for about 13 percent of motor vehicle deaths. It is essential to design pedestrian-friendly vehicles and pedestrian protection systems to reduce pedestrian fatalities and injuries. To effectively assess pedestrian injuries resulting from vehicle impact, a deformable pedestrian model must be developed for vehicle-pedestrian collision analysis. This study constructs a pedestrian-collision numerical model based on LS-DYNA finite element code. To verify the accuracy of the proposed deformable pedestrian model, experimental data are used in the pedestrian model test. This study applies the proposed model to analyze the dynamic responses and injuries of pedestrians involved in collisions. The modeled results can help assess vehicle pedestrian friendliness and assist in the future development of pedestrian-friendly vehicle technologies.  相似文献   
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