• Journal of the Korean Society for Precision Engineering
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• v.28 no.5
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• pp.572-577
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• 2011

Curve squealing of inter-city railway vehicle is a noise with high acoustic pressure and rather narrow frequency spectra. This noise turns out to be very annoying for the people living in the neighborhood of locations and the passenger in railway vehicle where this phenomenon occurs. Squealing is caused by a self-exited stick-slip oscillation in the wheel-rail contact. Curve squeal noise of railway vehicles that passed by a factor of the speed limit, so to overcome in order to improve running performance is one of the largest technology. In the present paper, characteristic of squeal noise behavior at the Hanvit-200 tilting train test-site. Curve squealing of railway wheels/rail contact occurs in R400~ R800 curves with a frequency range of about 4~11 kHz. If the curve is less than the radius of wheel frail contact due to |left-right| noise level difference (dBA) shows a significant effect of squeal noise were more likely.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.1
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• pp.85-93
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• 2009

There are many curves in Seoul subway system. Therefore, the noise from subway system in curved line gives displeasure to passenger. The subway noise in curved line is affected not only by rail condition but also wheel condition and dynamic characteristics. The railway curving noise can be divided into 2 categories. The first is the noise due to stick-slip between wheel tread and rail head, and the second is one by wheel flange contact on rail side. Because of these phenomena - stick-slip and wheel flange contact - wheels are worn seriously. In this study the curving noise was reviewed by using eigen-mode of wheel and waterfall plot which shows noise level in time-frequency domain. And also those were reviewed in viewpoint of stick-slip noise and wheel flange contact noise. Finally, the relationship between curving noise and wheel wear was studied.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.285-295
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• 2016

A contact strip shape of a high speed train pantograph system was optimized with CFD to increase the aerodynamic performance and stability of contact force, and the results were validated by a wind tunnel test. For design of the optimal contact strip shape, a Kriging model and genetic algorithm were used to ensure the global search of the optimal point and reduce the computational cost. To enhance the performance and robustness of the contact strip for high speed pantograph, the drag coefficient and the fluctuation of the lift coefficient along the angle of attack were selected as design objectives. Aerodynamic forces were measured by a load cell and HWA (Hot Wire Anemometer) was used to measure the Strouhal number of wake flow. PIV (Particle Image Velocimetry) was adopted to visualize the flow fields. The optimized contact strip shape was shown a lower drag with smaller fluctuation of vertical lift force than the general shaped contact strip. And the acoustic noise source strength of the optimized contact strip was also reduced. Finally, the reduction amount of drag and noise was assessed when the optimized contact strip was applied to three dimensional pantograph system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.3
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• pp.253-263
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• 2012

With the local Hertz deformation on the contact point, the dynamic contact between a high-speed wheel and an elastic beam having a gap is numerically analyzed by solving the whole equations of motion of the wheel and the beam subjected to the contact condition. For the stability of the time integration the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Especially the acceleration contact condition on the gap is formulated, and it is demonstrated that the contact force variation computed by the velocity contact constraint or by the acceleration contact constraint agrees well with that computed by the displacement contact constraint. The numerical examples show that, when the wheel passes on the gap, the solution is governed by the stiffness of the local Hertzian deformation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.780-785
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• 2001

A method for accurate measurement of the contact force in the current collection system of the high-speed railway is developed. In order to measure the contact force with minimal modifications to the pantograph, strain gauges are attached to the bottom of the contact strip. An algorithm for deriving the magnitude and stagger of the contact force from the bending strain measurements is devised. For the sample pantograph, the static contact forces are measured to within ${\pm}$5 % error for the magnitude and ${\pm}$ 2cm error for the stagger. For dynamic contact force measurement, it is found that the contact strip can the regarded as a rigid body for the contact frequency of less than 15 ㎐.

• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.497-506
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• 2020

CA mortar layer disengagement will give rise to the overall structural changes of the track and variation in the vibration form of the ballastless track. By establishing a vehicle-track-viaduct coupling analysis and calculation model, it is possible to analyze the CRTS-I type track structure vibration response while the track slab is disengaging with the power flow evaluation method, to compare the two disengaging types, namely partial contact loss at one edge beneath track slab and partial contact loss at midpoint beneath track slab. It can also study how the length of disengaging influences the track structures vibration power. It is showed that when the partial contact loss beneath track slab, and the relative vibration energy level between the rail and the track slab increases significantly within [10, 200]Hz with the same disengaging length, the partial contact loss at one edge beneath track slab has more prominent influence on the vibration power than the partial contact loss at midpoint beneath track slab. With the increase of disengaging length, the relative vibration energy level of the track slab grows sharply, but it will change significantly when it reaches 1.56 m. Little effect will be caused by the relative vibration energy level of the viaduct. The partial contact loss beneath the track slab will cause more power distribution and transmission between the trail and track slab, and will then affect the service life of the rail and track slab.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.924-929
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• 2001

The flying height of contact slider is determined by vertical and pitching motions of slider. This paper performed the computer simulation for flying height change of contact slider. It is changed by many parameters, contact stiffness, contact damping, air bearing stiffness ratio, a location of mass center, and so on. Computer simulation is performed for knowing for what change of these parameters influences in flying height of contact slider. Disk surface is modeled in harmonic wave with from 10㎑ to 600㎑. Tri-pad slider is modeled in that contact slider has 2-DOF motion (vertical motion, pitching motion). Tri-pad contact slider is analyzed by numerical analysis method in computer simulation.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.161-164
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• 2010

The surface roughness of wheels and rails are known to be major contributory factors in wheel-rail rolling noise. Generally, the rail roughness was greater than the wheel roughness. Generally, rolling noise sizes and noise level in compliance with wheel/rail roughness almost are reported with the fact that is similar. Rolling noise important factors rightly being in compliance with roughness of contact point regions of the wheel/the rail, presented from the present paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1350-1353
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• 2007

An experimental method based on contact resonance is developed to extract the contact parameters of mechanical joints under various clamped conditions. Mechanical joint parameters of shear contact stiffness and damping were extracted for different physical joint parameters such as surface finish of the mating surfaces, the presence of lubrication, the effect of the clamping pressure, and shear load. It was found that the shear contact stiffness values decreased with increasing clamping load and increased with increasing shear loading. Contact damping ratio values were almost constant with clamping load, but decreased with increasing shear load. Moreover, rough surfaces exhibited the highest shear stiffness and contact damping compared to smooth surfaces.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.160-165
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• 2002

The flying height of contact slider is determined by vertical and pitching motions. This paper performed the computer simulation for flying height change of contact slider. It is changed by many parameters, contact stiffness. contact damping, all bearing stiffness ratio and so on. So computer simulation analysis is performed for knowing for what change of these parameters influences in flying height of contact slider. The practical recording zone surface is gotten by using SPM. In recording zone, flying height is simulated for each parameter. the settling time which the flying height of contact slider is lower than 10nm is analyzed over practical disk surface for changing each parameter. Through these results, the contact slider can be analyzed for more accuracy dynamic characteristics.