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991.
Buses are an integral part of the national transportation system of each country. A rollover event is one of the most important
hazards that concerns the safety of the passengers and the crew in a bus. In the past, it was observed after the accident
that the deforming superstructure seriously threatens the lives of the passengers. Thus, the stiffness of the bus frame is
the first thing that needs to be considered. The unfortunate side of strengthening the bus superstructure is that it usually
causes the bus weight to increase. This paper presents an efficient and robust analysis method with which to design the bus
superstructure for a reduction in occupant injuries from rollover accidents while the weight of the strengthened bus is maintained
at the same level. First, the absorbed energy of the bus frame and its components during a rollover were investigated by using
a LS-DYNA numerical study. The highest energy absorption region, which is the side section of the bus frame, was found and
focused on for the investigation of a means to re-distribute the energy-absorption ability of the side frame component. Then
the thickness parameters that were obtained from the re-distribution of the energy-absorption ability were used in the analysis
to optimize the design. Finally, a prototype of the bus with a reasonable thickness for the window pillars and the side wall
bars, which was based on the optimized parameters, was verified to ensure it satisfied ECE R66. In this paper, an effective
usage of materials and an efficient and robust analysis method were presented to design the bus superstructure. Although the
optimization process for increasing the stiffness is simple, this study improves the upper displacement by 39.9% and the lower
displacement by 49.3% (versus the bus survivor space) while maintaining the bus weight at the existing level. 相似文献
992.
R. A. Sindhu M. K. Park S. J. Lee K. D. Lee 《International Journal of Automotive Technology》2010,11(6):857-863
This study was conducted to determine whether the different residual stresses caused by different welding speeds affect the
static and fatigue strength of laser-welded lap joints. Residual stresses in STS301L laser-welded lap joints of different
thicknesses under two laser-welding speed conditions, 4.1 m/min and 5.1 m/min, were evaluated with the incremental hole-drilling
strain gage method at the middle of the heat-affected zone (HAZ). Then, static and fatigue tests were performed. The results
show that higher static and fatigue strengths were obtained from the specimens welded with a 4.1 m/min welding speed than
from the specimens welded at 5.1 m/min. The main difference was due to the compressive principal residual stress magnitude
and its orientation near the HAZ. Also, the micro-hardness profile along the failure interface was measured to verify the
static and fatigue failure behavior. 相似文献
993.
Improvement of drivability and fuel economy with a hybrid antiskid braking system in hybrid electric vehicles 总被引:1,自引:0,他引:1
J. L. Zhang Ch. L. Yin J. W. Zhang 《International Journal of Automotive Technology》2010,11(2):205-213
When braking on wet roads, Antilock Braking System (ABS) control can be triggered because the available brake torque is not
sufficient. When the ABS system is active, for a hybrid electric vehicle, the regenerative brake is switched off to safeguard
the normal ABS function. When the ABS control is terminated, it would be favorable to reactivate the regenerative brake. However,
recurring cycles from ABS to motor regenerative braking could occur. This condition is felt to be unpleasant by the driver
and has adverse effects on driving stability. In this paper, a novel hybrid antiskid braking system using fuzzy logic is proposed
for a hybrid electric vehicle that has a regenerative braking system operatively connected to an electric traction motor and
a separate hydraulic braking system. This control strategy and the method for coordination between regenerative and hydraulic
braking are developed. The motor regenerative braking controller is designed. Control of regenerative and hydraulic braking
force distribution is investigated. The simulation and experimental results show that vehicle braking performance and fuel
economy can be improved and the proposed control strategy and method are effective and robust. 相似文献
994.
In this paper, a numerical procedure to estimate the performance of the high power pretensioner used in the seatbelt of a
passenger vehicle is presented. The data on the gas explosion pressure in a 10-cc volume and the data on the displacement
of the rack according to time were applied to the numerical procedure. The procedure was implemented using MATLAB. The testing
device, which met the automobile industry standards, was created. Experiments were carried out seven times under the same
conditions, and the mean values of the web retraction and belt load were used as the representative data. By comparing the
simulation results to the test results, the numerical procedure presented in this paper was verified. 相似文献
995.
A. Gauchia V. Diaz M. J. L. Boada B. L. Boada 《International Journal of Automotive Technology》2010,11(1):41-47
In this paper, the structural optimization of a real bus structure is proposed. The proposed optimization has been accomplished
by means of genetic algorithms. The structural behavior of the bus structure when subjected to weight and torsion was also
analyzed using the finite element method (FEM). The results demonstrate that improved weight and torsional stiffness are achieved
with the optimized structure. 相似文献
996.
Until recently, passenger cars have primarily interested in pedestrian protection performance. Nowadays, however, it is important
for a sport-utility vehicle (SUV) to meet the bumper system standards for pedestrian safety. For a SUV bumper system, there
are some difficulties in attaining a high level of pedestrian performance for the lower legform. An SUV has a high bumper
position from the ground level, and the bumper approach angle must also be secured, which has an effect on car insurance fees.
Due to these reasons, it is difficult to meet the pedestrian performance of the lower legform for an SUV. In this paper, a
comparative study was performed on various SUV bumper systems, and a concept model for a SUV bumper system was developed,
which is expected to meet the pedestrian performance by using the Pugh method. The design control factors were defined to
affect the bumper pedestrian performance through the experiences of tests and analyses. For the noise factor to affect the
pedestrian performance, the deviation of the impactor position was selected at the moment of impact. The design control factors
were optimized by using the Taguchi optimization technique. For the Taguchi method, an L18 orthogonal array table of design
control factors was used in the optimization process. Particularly, for the optimization of the bumper corner region, an optimization
analysis was performed three times to meet pedestrian performance. Based on the results of the Taguchi optimization method,
the sensitivity of the bumper design parameters was studied, and a new SUV bumper system is proposed that satisfies the pedestrian
performance of the lower legform. The optimized bumper system should obtain a full Euro-NCAP score of 6 points for the bumper
test. The pedestrian performance of the optimized bumper system is validated by using a CAE (Computer Aided Engineering) analysis,
which has been proven to be in accurate. A comparison between the test and analysis results is shown for the validation of
accuracy. By using the optimized bumper system, the tests and development costs of a bumper can be reduced. 相似文献
997.
Recently, the demands for improved fuel economy have been continually rising because of environmental protection policies,
legislative pressures on emissions and increases in the price of oil. Reducing the friction power loss in a production engine
may be regarded as one of the most effective technologies for improving fuel economy because the technology is cost effective
and applicable to a great number of vehicles. This paper describes attempts to measure the torque needed to drive a camshaft
and to examine the sources of the torque fluctuations in order to analyze the friction in valvetrains. The measurements were
performed through a cam sprocket-type torquemeter, which was able to measure the torque of the valvetrain under actual engine
operating conditions. In the cam torque measured, the fluctuations were mainly dependent on the primary oscillations caused
by cam events and the secondary oscillations caused by the valvetrain natural frequency. The range of the fluctuations became
greater at high speed because of the inertial mass. The resulting FMEP (friction mean effective pressure) of the valvetrain
decreased, and the effective peak tension increased with an increase in the engine speed. 相似文献
998.
Subjective well-being related to satisfaction with daily travel 总被引:1,自引:0,他引:1
Cecilia Jakobsson Bergstad Amelie Gamble Tommy Gärling Olle Hagman Merritt Polk Dick Ettema Margareta Friman Lars E. Olsson 《Transportation》2011,38(1):1-15
Previous research demonstrates an impact on subjective well-being (SWB) of affect associated with routine performance of out-of-home
activities. A primary aim of the present study is to investigate whether satisfaction with daily travel has a positive impact
on SWB, either directly or indirectly through facilitating the performance of out-of-home activities. A secondary aim is to
determine whether emotional-symbolic or instrumental reasons for car use results in higher satisfaction with daily travel
than other travel modes. A survey of a population-based sample of 1,330 Swedish citizens included measures of car access and
use, satisfaction with daily travel, satisfaction with performance of out-of-home routine activities, and affective and cognitive
SWB. The results confirmed that the effect on affective and cognitive SWB of satisfaction with daily travel is both direct
and indirect via satisfaction with performance of activities. Percent weekly car use had a small effect on satisfaction with
daily travel and on affective SWB, although fully mediating the effect of satisfaction with performance of the activities.
This suggests that car use plays a minor role for satisfaction with daily travel and its effect on SWB. This role may be larger
if investigated after a forced reduced car use. 相似文献
999.
A unique set of activity scheduling data is utilized in this paper to provide much needed empirical analysis of the sequence
in which activities are planned in everyday life. This is used to assess the validity of the assumption that activities are
planned in accordance to a fixed hierarchy of activity types: mandatory activities first (work/school), followed by joint maintenance, joint discretionary, allocated maintenance, and
individual discretionary activities. Such an assumption is typical of current generation activity and tour-based travel demand
models. However, the empirical results clearly do not support such assumptions. For instance, fewer than 50% of mandatory
activities were actually planned first in related out-of-home tours; remaining activity types also did not take any particular
precedence in the planning sequence. Given this, a search was made for the more salient attributes of activities (beyond activity
type) that would better predict how they are planned within tours. Several ordered response choice models for different tour
sizes were developed for this purpose, predicting the choice order of the 1st, 2nd, 3rd, etc. planned activity in the tour
as a function of activity type, activity characteristics (duration, frequency, travel time, and involved persons), and individual
characteristics. Activity duration played the most significant role in the models compared to any other single variable, wherein
longer duration activities tended to be planned much earlier in tours. This strongly suggests that the amount of time-use,
rather than the nature of the event as indicated by activity type, is a primary driver of within-tour planning order and offers
potential for a much improved and valid fit. 相似文献
1000.
We develop a short turning model using demand information from station to station within a single bus line-single period setting,
aimed at increasing the service frequency on the more loaded sections to deal with spatial concentration of demand considering
both operators’ and users’ costs. We find analytical expressions for optimal values of the design variables, namely frequencies
(inside and outside the short cycle), capacity of vehicles and the position of the short turn limit stations. These expressions
are used to analyze the influence of different parameters in the final solution. The design variables and the corresponding
cost components for operators and users (waiting and in-vehicle times) are compared against an optimized normal operation
scheme (single frequency). Applications on actual transit corridors exhibiting different demand profiles are conducted, calculating
the optimal values for the design variables and the resulting benefits for each case. Results show the typical demand configurations
that are better served using a short turn strategy. 相似文献