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Research Papers

On the Replacement of Shoe-Wheel Brakes by Pad-Disk for Railroad Freight Cars

[+] Author and Article Information
Sergio José Romano

Railway Laboratory Consultant
e-mail: sjromano@uol.com.br

Francisco de Carvalho Santos

Railway Laboratory Consultant
e-mail: carvalho16@uol.com.br

Auteliano A. Santos

e-mail: aute@fem.unicamp.br
School of Mechanical Engineering – Unicamp,
Rua Mendeleyev, 200,
13083-860 Campinas (SP), Brazil

www.fem.unicamp.br/∼lafer.

Manuscript received September 13, 2012; final manuscript received April 25, 2013; published online October 21, 2013. Assoc. Editor: Ranganathan Kumar.

J. Thermal Sci. Eng. Appl 6(1), 011002 (Oct 21, 2013) (8 pages) Paper No: TSEA-12-1152; doi: 10.1115/1.4024701 History: Received September 13, 2012; Revised April 25, 2013

Most of railroad freight cars use brake shoes directly applied onto the wheels. This system causes wheel heating, which in turn gives rise to thermal stresses and loss of mechanical strength. An alternate solution is a system of brake disks and pads, which would not heat the wheels, like disk brakes. Because temperature is one major factor affecting braking performance, a study of the viability of replacing shoe brakes by disk brakes must evaluate and compare the heating of wheels and disks. The present work evaluates the heating of disk-pad systems when used for braking freight cars in the same conditions regularly applied to shoe-wheel brakes. In addition, stop distance for both systems are evaluated for regular speeds of freight railroads. Preliminary numerical simulations were done to choose the critical brake condition and to check whether the expected temperatures would exceed the temperature limits, damaging the friction materials and systems. Following that, real scale tests were conducted in critical braking conditions for both types of brake systems. Dynamometer tests were performed in real scale at the Railroad Laboratory of the State University of Campinas, Brazil. Results showed that, as far as system heating is concerned, there is nothing to prevent the replacement of the current system by a disk-pad system. Besides, the stop distance for both systems is also in the recommended range.

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References

Figures

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Fig. 1

Wheel finite element grid generated by the ansys@ software

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Fig. 2

Disk finite element grid generated by the ansys@ software. Detail of the evaluated section.

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Fig. 3

Dynamometer of the Railroad Laboratory of the Department of Mechanical Design, Faculty of Mechanical Engineering, Unicamp

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Fig. 4

Temperature simulation results on wheel surface for heavy grade as a function of braking time ( °C)

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Fig. 5

Wheel temperature distribution for heavy grade condition ( °C)

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Fig. 6

Results of temperature calculation on the disk surface for heavy grade condition ( °C)

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Fig. 7

Disk temperature distribution for heavy grade condition ( °C)

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Fig. 8

Temperature variation of shoe-wheel pair, heavy grade SF 11 test ( °C)

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Fig. 9

Temperature variation of shoe-wheel pair, heavy grade SF 12 test ( °C)

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Fig. 10

Temperature variation of shoe-wheel pair, heavy grade SF 16 test ( °C)

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Fig. 11

Temperature variation of pad-disk friction pair, heavy grade M03 test

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Fig. 12

Theoretical–experimental comparison of temperature variation for pad-disk friction pair

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Fig. 13

Friction coefficient variation for the shoe-wheel friction pair, heavy grade SF 11 test

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Fig. 14

Friction coefficient variation for the disk-pad friction pair, heavy grade M03 test

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Fig. 15

Theoretical–experimental comparison of temperature variation for the shoe-wheel friction pair (SF11)

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