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951.
952.
S. R. Sin S. M. Yang H. S. Yu C. W. Kim H. Y. Kang 《International Journal of Automotive Technology》2008,9(1):81-86
The welding quality of spot weldment is an important factor that significantly affects the strength, stiffness, safety, and
other performance characteristics of vehicles. Therefore, quality control and fatigue life evaluation of spot weldment are
necessary processes. This paper presents a method for determining the fatigue life of multi-lap spot weldment of a high strength
steel sheet. In this method, the fatigue life is estimated using the lethargy coefficient, which is the total defect coefficient
according to rupture stress and time obtained by the quasi static tensile-shear test. The DC potential drop method was used
to check initiation and propagation of cracks in addition to the test. Also, in this study, we modified the lethargy coefficient
by using the welding current. Furthermore, we define a specific lapping constant, which is a characteristic constant of 2
or 3 lap weldments. The fatigue life obtained by the fatigue estimate equation, which contains a specific lapping constant
was compared and verified with an experimental value. Finally we analyzed the relation of lap number, welding current and
fatigue life. This method can save processing time and cost for predicting the life cycle of a structure. 相似文献
953.
This paper presents the road simulator control technology for reproducing a road input signal to implement real road data.
The simulator consists of a hydraulic pump, a servo valve, a hydraulic actuator and its control equipment. QFT (Quantitative
Control Theory) is utilized to control the simulator effectively. The control system illustrates a tracking performance of
the closed-loop controller with a low order transfer function G(s) and a pre-filter F(s) for a parametric uncertainty model. A force controller is designed to communicate the control signal between the simulator
and digital controller. Tracking specification is satisfied with upper and lower bound tolerances on the steep response of
the system to the reference signal. The efficacy of the QFT force controller is verified through the numerical simulation
in which combined dynamics and actuation of the hydraulic servo system are tested. The simulation results show that the proposed
control technique works well under an uncertain hydraulic plant system. The conventional software (Labview) is used to make
up for the real controller on a real-time basis, and the experimental works show that the proposed algorithm works well for
a single road simulator. 相似文献
954.
J. W. Chung J. H. Kang N. H. Kim W. Kang B. S. Kim 《International Journal of Automotive Technology》2008,9(1):1-8
Currently, due to the severity of world-wide air pollution by substances emitted from vehicles, emission control is being
enforced more strictly, and it is expected that the regulation requirements for emission will become even more severe. A new
concept combustion technology that can reduce the Nitrogen oxides (NOx) and PM in relation to combustion is urgently required.
As a core combustion technology among new combustion technologies for the next generation engine, the homogenous charge compression
ignition (HCCI) is expanding its application range by adopting a multiple combustion mode, a catalyst, direct fuel injection
and partially premixed charge compression ignition combustion using the split injection method. This paper used a split injection
method in order to apply the partially premixed charge compression ignition combustion method without significantly altering
engine specifications of the multiple combustion mode and practicality by referring to the results of studies on the HCCI
engine. Furthermore, the effects of the ratio of the fuel injection amount on split injection are investigated. From the test
results, the adequate combination of the ratio of the fuel injection amount for the split injection method has some benefit
on exhaust and fuel economy performance in a naturally aspirated single cylinder diesel engine. 相似文献
955.
S. P. Jung K. J. Jun T. W. Park J. H. Yoon 《International Journal of Automotive Technology》2008,9(1):45-51
It is quite challenging to estimate the braking performance of a vehicle because the brake system is comprised of many parts,
including a booster, master cylinder, and caliper. Calculation of characteristics such as braking force through vehicle tests
requires much time and money. Therefore, the development of a method to estimate the braking performance of a vehicle using
qualitative methods is beneficial. In this study, a program that can analyze the braking capabilities of a vehicle such as
pressure, efficiency, and pedal travel is presented. The increase in disc temperature during braking as well as the properties
of various boosters can be calculated using the proposed program. Dynamic characteristics of a vehicle equipped with a Load
Sensing Proportional Valve (LSPV) were computed more precisely by obtaining the change in valve pressure according to the
displacement of a suspension system. Since all input and output files are composed in the Microsoft Excel format, both design
data management and database construction can easily completed. 相似文献
956.
D. Jung W. L. Wang A. Knafl T. J. Jacobs S. J. Hu D. N. Assanis 《International Journal of Automotive Technology》2008,9(1):9-15
The effects of the Abrasive Flow Machining (AFM) process on a direct injection (DI) Diesel engine fuel injector nozzle are
studied. Geometry characterization techniques were developed to measure the microscopic variations inside the nozzle before
and after the process. This paper also provides empirically-based correlations of the nozzle geometry changes due to the AFM
process. The resulting impact of the process on the engine performance and emissions are also assessed with a DI Diesel engine
test setup. This study shows that properly AFM-processed injectors can enhance engine performance and improve emissions due
to the improved quality of the nozzle characteristics. However, an extended process can also cause enlargement of the nozzle
hole as a side effect, which can adversely affect emissions. Emission measurements show the trade-off for the minimum levels
as the process proceeds. Since the enlargement of the hole during the AFM process is not avoidable and must be minimized,
strict control over the process is required. This control can be enforced by either limiting the AFM processing period, or
by properly preparing the initial hole diameter so as to accommodate the inevitable changes in the nozzle geometry. 相似文献
957.
H. -M. Kim S. -K. Park K. -S. Choi H. -M. Wang D. -H. Lee D. -K. Lee Y. -S. Cha J. -S. Lee J. Lee 《International Journal of Automotive Technology》2008,9(2):149-153
An important goal in diesel engine research is the development of a means to reduce the emissions of nitrogen oxides (NOx).
The use of a cooled exhaust gas recirculation (EGR) system is one of the most effective techniques currently available for
reducing nitrogen oxides. Since PM (Particulate Matter) fouling reduces the efficiency of an EGR cooler, a tradeoff exists
between the amount of NOx and PM emissions, especially at high engine loads. In the present study, we performed engine dynamometer
experiments and numerical analyses to investigate how the internal shape of an EGR cooler affects the heat exchanger efficiency.
Heat exchanger efficiencies were examined for plain and spiral EGR coolers. The temperature and pressure distributions inside
these EGR coolers were obtained in three dimensions using the numerical package program FLUENT. 相似文献
958.
The sub-chamber type gasoline engine was suggested to be a type of clean engine, but the presence of residual gas in the sub-chamber
was a serious fault. In this experimental study, the CNG direct injection method was applied to scavenge residual gas from
the sub-chamber. The CVC (constant volume chamber) is divided into the sub-chamber and main-chamber and used as the main experimental
apparatus. Because each combustion chamber of the CVC has an injector, the injector can be used freely, at the same time or
individually. Therefore, the scavenging efficiency can be improved by changing injection times for the sub-chamber. The experimental
results demonstrated that when all the fuel was injected into the sub-chamber, the combustion duration was shortened by 30%
compared to that of injection into the main-chamber. Although residual gas was observed in the CVC, when the frequency of
injections into the sub-chamber increased, good combustion characteristics were obtained. 相似文献
959.
J. W. Lee Y. I. Jeong M. W. Jung K. O. Cha S. I. Kwon J. C. Kim S. Park 《International Journal of Automotive Technology》2008,9(4):397-403
In recent years, particle number emissions rather than particulate mass emissions in automotive engines have become the subject
with controversial discussions. Recent results from studies of health effects imply that it is possible that particulate mass
does not properly correlate with the variety of health effects attributed to engine exhaust. The concern is now focusing on
nano-sized particles emitted from I. C. engines. In this study, particulate mass and particle number concentration emitted
from light-duty vehicles were investigated for a better understanding of the characteristics of the engine PM from different
types of fuels, such as gasoline and diesel fuel. Engine nano-particle mass and size distributions of four test vehicles were
measured by a condensation particle counter system, which is recommended by the particle measurement program in Europe (PMP),
at the end of a dilution tunnel along a NEDC test mode on a chassis dynamometer. We found that particle number concentrations
of diesel passenger vehicles with DPF system are lower than gasoline passenger vehicles, but PM mass has some similar values.
However, in diesel vehicles with DPF system, PM mass and particle number concentrations were greatly influenced by PM regeneration.
Particle emissions in light-duty vehicles emitted about 90% at the ECE15 cycle in NEDC test mode, regardless of vehicle fuel
type. Particle emissions at the early cold condition of engine were highly emitted in the test mode. 相似文献
960.
J. -Y. Zhang J. -W. Kim K. -B. Lee Y. -B. Kim 《International Journal of Automotive Technology》2008,9(6):695-702
This paper investigates an active front steering control strategy based on quantitative feedback theory (QFT). By incorporating
feedback from a yaw rate sensor into the active steering system, the control system improves the dynamic response of the vehicle.
The steering response of a vehicle generally depends upon uncertain quantities like mass, velocity, and road conditions. Thus,
QFT is used to design a controller with robust performance. A multi-degree-of-freedom nonlinear model is co-simulated here
by MATLAB Simulink and ADAMS/CAR. The performance of the control system is evaluated under various emergency maneuvers and
road conditions. The result shows that the designed robust control system has good control performance and can efficiently
improve handing qualities and stability characteristics. 相似文献