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- 2019
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Tidskriftsartikel (refereegranskat)
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- Singh Walia, Mandeep, 1987
(författare)
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Mechanical braking systems for trains: A study of temperatures, fatigue and wear by experiments and simulations
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increased demand for shorter travel times, higher axle loads, increased volumes and increased punctuality of railway traffic calls for a better design and management of the railway subsystems. The present thesis deals with aspects of mechanical friction brakes, in the form of tread brakes and disc brakes. These are critical for reliable, safe and economical operation of trains. The thesis establishes models and simulation tools for frictional braking systems that may operate in parallel with an electrodynamic braking system. A main focus is the influence of thermal loading on rolling contact fatigue from tread brakes at stop braking. A simulation methodology for thermomechanical cracking of railway wheel treads due to rolling contact and repeated stop braking by tread brakes, is established based on full-scale brake rig experiments. Building on the same approach, plastic deformation of the tread is also investigated. The results indicate that tread damage increases drastically for frictional temperatures above some 450 ºC. Another focus is temperatures and wear of tread brakes and disc brakes under operational loading. In two field test campaigns, detailed instrumentation and continuous measurements of relevant temperatures and braking parameters are combined with intermittent measurement of wear of friction brake components. Wear of brake blocks and wheel treads is quantified. It is found that the tread wear introduced by the block contact dominates for trailing wheelsets, whereas for powered wheelsets wear from tractive forces in the wheel–rail contact can be of equal importance. In a study on disc brakes, temperatures and wear performance are compared for two friction pairs: one new segmented disc with sintered pads and a traditional disc with an undivided friction ring combined with organic pads. It is found that the discs have similar braking temperatures, but that the wear of disc and pads is substantially lower for the segmented disc. A numerical investigation of thermomechanical fatigue damage of the two disc types indicates that the segmented disc also has a substantially longer fatigue life.
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- Singh Walia, Mandeep, 1987, et al.
(författare)
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Temperatures and wear at railway tread braking: Field experiments and simulations
- 2019
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 440-441
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Tidskriftsartikel (refereegranskat)abstract
- Field tests were carried out for a commuter train in revenue service equipped with cast iron and organic composite brake blocks. Temperatures for wheel tread, wheel web and brake blocks and wear of wheel treads and brake blocks were recorded. The measured temperatures are used for calibrating a thermal model for assessment of wheel and block temperatures. The wear of cast iron and organic composite brake blocks is estimated using simulated temperatures and temperature-dependent wear models based on pin-on-disc experiments. It is found that a wear rate adaption factor, tentatively motivated by the presence of thermoelastic instabilities at full-scale braking that cannot be found at small-scale testing, is required for producing a simulated wear that is in agreement with results from field tests. Wheel tread wear is assessed as change in flange height for both powered and trailing wheels and for the studied train it is found that the levels of annual total wear of these types of wheels are similar in magnitude. Modelling of the tread wear originating from block–wheel contact and wheel−rail contact, combined with a comparison with measured wear magnitudes, makes it possible to quantify the wear from these two tread contacts. It is found for the powered wheels that wear induced by the wheel-rail contact and the block-wheel contact have equal importance, whereas for the trailer wheels the wear emanating from the block-wheel contact is dominating.
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- Walia, Mandeep Singh, 1987, et al.
(författare)
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Wear and plastic deformation of the wheel tread at block braking : Results from brake rig experiments and simulations
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the present work, results from a series of full-scale tread braking experiments that include a wheel–railwheel rolling contact, are compared to the results from FE simulations with focus on tread plasticity and wear. Brake rig tests have been performed to reveal tread plasticity and tread wear in the form of sequences of constant temperature rolling at 200 °C, 250 °C, and 300 °C, all for a wheel–railwheel contact load of 60 kN. The evolution of the tread profile is measured during the experiments and is compared to estimations from the FE simulations and wear calculations. Finally, calculated tread wear introduced by braking and specific influence from rolling contact plasticity on the tread profile evolution are estimated and compared to the measured wear.
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