• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.177-185
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• 2013

A new theoretical derailment coefficient model of wheel-climb derailment is proposed to consider the influence of wheel unloading. The derailment coefficient model is based on the theoretical derailment model of a wheelset that was developed to predict the derailment induced by train collisions. Presently, in domestic derailment regulations, a derailment coefficient of 0.8 is allowable using Nadal's formula, which is for a flange angle of $60^{\circ}$ and a friction coefficient of 0.3. However, theoretical studies focusing on different flange angles to justify the derailment coefficient of 0.8 have not been conducted. Therefore, this study theoretically explains a derailment coefficient of 0.8 using the proposed derailment coefficient model. Furthermore, wheel unloading of up to 50% is accepted without a clear basis. Accordingly, the correlation between a wheel unloading of 50% and a derailment coefficient of 0.8 is confirmed by using the proposed derailment coefficient model. Finally, the validity of the proposed derailment coefficient model is demonstrated through dynamic simulations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.10
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• pp.1207-1218
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• 2013

It is difficult to predict derailment with the existing derailment coefficient like Nadal's formula which is based on the contact forces between one wheel and rail. A new derailment coefficient model developed on a wheelset is able to make a better estimate about the climb derailment, slip derailment, roll over derailment, and mixed derailment types of these. Moreover, not only the mechanical factors considered in the existing derailment coefficients but also other various factors affecting derailment such as wheel unloading and loading, diameter of wheel, and locations of axle-box bearings can be covered with this new derailment coefficient model. That is, the derailment patterns which couldn't be solved with the existing formulas such as Nadal's and Weinstock's models can be analyzed with this wheelset derailment coefficient model because of considering various factors causing derailment. Finally, the validity of the new derailment coefficient model is verified using dynamic model simulations.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.306-312
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• 2007

The running safety of rolling stock is assessed by derailment coefficient. It requires lots of preparatory time, expenditure and high measurement technique to measure derailment coefficient. If derailment coefficient could be measured when track or vehicle is maintained, safety will be improved. The measurement and assessment of running safety is necessary for safety especially for the vehicles newly developed and started service. Therefore measurement of derailment coefficient is most important thing to secure running safety. In this paper, we examined new assessment method which could estimate derailment coefficient by measuring vibration acceleration and displacement of vehicle operating at actual track irrespective of time and place. The new method could be used effectively as a mean confirming running safety.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.228-233
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• 2004

A derailment coefficient of railway vehicle is as one of important element that estimate running safety. Derailment coefficient is ratio of lateral load/vertical load happens in contact point between wheel and rail. Lateral load increases, dangerous of derailment can rise. There are ground and vehicle to measurement method of these derailment coefficient. Method of ground is simple, but when vehicles passes data of a point, there is shortcoming that acquire locally. Curved surface style wheel shape that use so far among vehicle method in this research wishes to be not but describe about static load test of wheel-set for derailment coefficient measurement that have plane plate shape that manufacture separate way and correction result etc. to test.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.953-958
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• 2007

To assess the derailment safety of the Samaeul Train, We developed a fleet analysis model and carried out sensitivity analysis of the variables related to derailment factors with ADAMS/Rail computing analysis method. Depending on the variation of the running speed in curve section, derailment coefficient and wheel load reduction rate are high at right side wheels in slow running speed section and low at left side wheel in high running speed. According to decreasing the radius of curve, derailment coefficient and wheel load decreasing rate are increased. Derailment coefficient is proportional to transition curve length and wheel load decreasing rate is constant. Cant value rising causes wheel load deduction rate rising.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.745-750
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• 2004

For the safety of railway, it should be evaluated for the running safety by measuring the derailment coefficient. Although railway has run the fixed and maintained rail, some of railway is derailed. This report shows the results that performed the static load test, wheelset manufacturing for test, main line running test on the basis of the derailment theory and experience. It is executed main line test into more than 80km/h for estimating the curving performance and running safety of Gwangju EMU. As the test results, could confirm the curving performance and running safety of Gwangju EMU from the results of the wheel unloading, lateral force, derailment coefficient etc. Derailment coefficient was less than 0.8, and lateral force allowance limit and wheel load reduction ratio were enough safe.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.492-498
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• 2007

For the running safety assessment of Saemaul train passing through curves, an analysis model for multibody system has been developed. By using this model and ADAMS/Rail, sensitivity analyses depending on the variation of parameters related to the derailment coefficients have been conducted. At low speed, the derailment coefficient and the unload ratio of right wheel showed higher than left wheel, while those of left wheel showed higher than right wheel at high speed. According to decrease of curve radius, the derailment coefficient and the unload ratio were increased. When the length of transition curve was increased, the derailment coefficient was increased but there was no change on the unload ratio. According to the increase of cant, the derailment coefficient and the unload rate were increased.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1031-1035
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• 2007

When vehicles running, vertical force and lateral force act except load of vehicles to rail and wheel. This force happens by complex motion at running. If mark vertical force by P and lateral force by Q, derailment coefficient displays Q/P, most important indicator pointer of running safety judgment. If Q is grown than P from derailment coefficient, than arrived to derailment because wheel climb or jumps over rail. Wheel climb derailment among kind of derailment is when attack angle is +, wheel and rail strike and flange rides to rail. This derailment occurs much in curved line and occurs in low speed. In this study, occurred when running at low speed on curved line, analyze cause of derailment and presented the countermeasure plan.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.613-618
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• 2004

Is confirming safety of derailment when wish to develop new vehicles or upgrade running speed of vehicles. This means the measure of wheel load and lateral force that act between wheel and rail. So far, problem in continuous measuring method of derailment coefficient was sensitivity decline and noise growth. This research supplemented these problems by composition of new bridge circuit.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.243-249
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• 2000

This experimental study is shows speed-up possibility for the conventional railway vehicle. We appraise derailment coefficient then increase the velocity of the kyungbu line, honam line, changhang line, kyungjeon line.