• Journal of the Korean Society for Precision Engineering
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• v.24 no.7 s.196
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• pp.106-111
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• 2007

In this paper, the transient brake time was studied on the van type vehicle with accelerometer. Experiments were carried out on the asphalt(new and polished), unpacked road(earth and gravel) and on wet or dry road conditions. The transient brake time is not effected bzy the vehicle speed. The transient brake time is about 0.41$\sim$0.43second on the asphalt road surface and the error range is within 0.1$\sim$0.16second. For the asphalt road condition, the transient brake time is not effected by both new asphalt road surface and the polished asphalt road surface. With compared by dry and wet road surface condition, the transient brake time of wet condition is longer than dry road condition and compared with unpacked road condition and packed road condition, unpacked road condition is shorter than packed road condition. It is considered that the transient brake time is effected by the road surface fraction coefficient. In other words, the transients brake time increases as friction coefficient decreases.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.71-74
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• 2008

This paper aims at studying the key design elements for the optimal ventilation system design, developing the design models and suggesting the design guidelines. The key elements include the basic exhaust emission rate, wall friction coefficient, vehicle drag coefficient and slip streaming effect, jet fan operating efficiency, natural ventilation force and installation scheme for jet fans and ventilation monitors in tunnel. The design models developed in this study are one-dimensional ventilation simulator to analyze the air flow, pressure profile and pollutant dispersion inside and outside tunnel, expert model to choose the optimal ventilation method, and the ventilation characteristic chart to evaluate the preliminary ventilation system. The study results are reflected in the design guideline for road tunnel ventilation system.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.4
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• pp.19-29
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• 1995

This paper discusses the stick-slip phenomenon of the driveline system of a vehicle in consideration of friction. Friction is operated on the between of flywheel and clutch disk. The expressions for obtaining the results have been derived from the equation of motion of a three degree of freedom frictional torsion vibration system which is made up driving part(engine, flywheel), driven part(clutch, transmission) and dynamic load part(vehicle body) by applying forth-order Rungekutta method. It was found that the great affect parameters of the stick-slip or stick motion were surface pressure force between flywheel and clutch disk, time decay parameter of surface pressure force and 1st torsional spring constant of clutch disk when driveline system had been affected by friction force. The results of this study can be used as basic design data of the clutch system for the ride quality improvement of a car.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.139-143
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• 2019

In this study, we tried to derive the most severe scenario and its critical speed by 1-D collision simulation with a variable formation vehicle in order to prepare for the change of demand in Seoul Metropolitan Subway Line 3, which is operated by fixed arrangement. After establishing various collision scenario conditions, the friction coefficient between the wheel and the rail was evaluated as 0.3, which is considered to be severe. As a result of analysis according to all scenarios, the most severe scenario conditions were confirmed by comparing rubber shock absorber performance and vehicle collision deceleration. In addition, a typical wheel-rail friction coefficient was derived through accident cases, and the analysis was performed again and compared. Finally, the criterion of the critical speed in the condition of the friction coefficient of the normal wheel - rail condition was confirmed.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.52-59
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• 2008

Most accident reconstruction or analysis depend on the coefficient of friction to estimate the vehicle speeds. Skid mark and coefficient of friction are usually utilized to calculate the velocity and behavior of vehicles. For a critical case such as traffic accident reconstruction, however, the initial velocity of the car should be calculated precisely. In this paper, emergency brake tests on ABS and Non-ABS brake system are conducted on the dry pavement asphalt road on speed 40, 60, 80 and 100 km/h respectively. The SWIFT sensor was established in the front wheel and rear wheel at driver side to measure the forces, moments and speeds of revolution of the tires. These tests results can be available to brake tests and accident reconstruction.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.613-618
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• 2007

The real vehicle crash experiment is the best way to evaluate the performance of a guardrail. However the experiment is very expensive because of high cost of vehicles and guardrail installation. Thus in this study, crash simulation of a vehicle against a steel guardrail is performed using LS-DYNA. There are many researches on the impact of a vehicle against a guardrail. However the friction between a vehicle and a guardrail is not considered, although it affects considerably the behavior of a guardrail. In this paper, the friction coefficient is applied to evaluate correctly the performance of a guardrail.

• Journal of Power System Engineering
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• v.11 no.2
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• pp.58-63
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• 2007

Vehicular safety and occupant injury have been of considerable interest to the public. The dynamic response of an articulated vehicle is different from that of single body vehicle due to its geometric and inertia properties. Articulated vehicles have the tendency to jackknife if they lose driving safety. Influence of factors for driving safety of an articulated vehicle(Tractor-Semitrailers) has been analysed by the EDVTS, a kinetic analysis program for an articulated vehicle. EDVTS permits an analyst to investigate the effect of many variables in a short period of time, and enables to obtain an accurate explanation of driving safety. The factors used in the analysis include the load, friction coefficient, tire flat, increase of braking force, and trailer geometry. Based on the results, the articulation angle and driving safety were influenced remarkably by the load, coefficient of friction, increase of braking force. However, trailer geometry, such as length and width, did not affect articulation angle and driving safety

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1761-1765
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• 2008

In the braking of a railroad car, mechanical brake systems using wheel tread and brake disk are applied as well as electrical brake systems by regenerator and rheostat. It is very important to consider the frictional characteristic because kinetic energy of the vehicle is dissipated as converted thermal energy through friction between disk and brake pad during disk braking. A friction coefficient and wear characteristic are decided from the interrelationship of disk and friction material in the disk brake system. Lab-scale dynamometer test on developed brake disk materials for increasing heat resistance was performed in this study. Each candidate material was tested at various braking speeds and pressures and we obtained the friction coefficient and wear characteristic. And we executed comparative evaluation of the result from the test.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.723-730
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• 2007

The typical design of automotive driveshafts generally utilizes Constant Velocity(CV) joints as a solution to NVH. CV joints are an integral part of vehicles and significantly affect steering, suspension, and vehicle vibration comfort levels. Thus, CV joints have been favored over universal joints due to the constant velocity torque transfer and plunging capability. Although CV joints are common in vehicle applications, current research works on modeling CV joint friction and assumes constant empirical friction coefficient values. However, such models are long known to be inaccurate, especially under dynamic conditions, which is the case for CV joints. In this paper, an instrumented advanced CV joint friction apparatus was developed to measure the internal friction behavior of CV joints using actual tripod-type joint assemblies. The setup is capable of measuring key performance of friction under different realistic operating conditions of oscillatory speeds, torque and joint installation angles. The apparatus incorporates a custom-installed triaxial force sensor inside of the joint to measure the internal CV joint forces(including friction). Using the designed test setup, the intrinsic interfacial parameters of CV joints were investigated in order to understand their contact and friction mechanisms. The results provide a better understanding of CV joint friction characteristics in developing improved automotive driveshafts.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.115-122
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• 2012

Automobile collision analysis is composed of various shapes, and the speed variation working to the vehicle during collision are utilized as a very important factor in evaluating the degree of vehicle collision or passenger safety. So, the method of analyzing result values on the speed variation utilizing collision analysis program become necessary. This study utilized PC-Crash program in order to compare actual values and analyzed values of braking distance with the friction coefficient of road surface according to vehicle velocity. As a result, the smaller friction coefficient found to be larger error, and the maximum error range of collision velocity in case of each different vehicles (MATIZ, SONATA, or BUS) at the intersection showed 1.2%, 1.8%, 3.1% according to the difference of vehicle weight. Moreover, an accidental fall at IN-CHEON large bridge in order to reappear was verified with practicing simulation which has a slight error.