Noise-related roughness of railway wheel treads-full-scale testing of brake blocks

Abstract

Results from full-scale tread braking experiments on an inertia dynamometer (brake testing machine) are presented. Eighteen prototypes of brake blocks are investigated. Two braking characteristics relating to the influence of the blocks on the wheel tread are studied: generation of hot spots and generation of roughness (corrugation, waviness). Wheel tread temperatures are measured during braking using an infrared (IR) technique. The wheel roughness is measured after each brake cycle when the wheel has cooled down. A roughness indicator, R ëCA , relates measured roughness to expected rolling noise as generated by the wheel in operation. A correlation between the spatial distributions of temperatures and roughnesses is normally found: stronger for cast iron blocks and composition blocks and weaker for sinter blocks. The cast iron blocks are found to produce high tread roughness levels, partly owing to material transfer from brake block to wheel tread. The composition blocks are found to result in lower roughness levels than the cast iron blocks. Finally, the sinter metal blocks are found to lead to the lowest roughness levels, a fact which is probably due to the abrasive property of these blocks. Friction coefficients during braking are also measured.

Influence of material properties on sliding contact braking applications

“…On the negative side for cast iron, one can mention problems with the development of the so-called "hot spots" on the rotor, which is a thermoelastic instability phenomenon. Experiments in [13] show that composition brakes can withstand higher thermal loads without hot spot formations. The formation of hot spots on a railway wheel is probably the stimulus for cladding, i.e.…”

Two-dimensional finite element simulation of the thermal problem at railway block braking

“…The experimental method is described in detail in reference [6]. The full-scale tread braking experiments are made on an inertia dynamometer (brake testing machine).…”

“…The full-scale tread braking experiments are made on an inertia dynamometer (brake testing machine). The same composition block as in reference [6] is studied here using the F E model. The wheel tread temperatures are measured using an infrared (IR ) technique (thermocamera).…”

“…small deviations of temperature in the transverse direction). The experimental data come from the measurements described in reference [6], where temperatures on a transverse line on the wheel surface just after passing the block are recorded. A mean value of these temperatures along the line is used for comparison with the calculated temperatures.…”

“…This non-even wear of the tread results, after cooling down, in a corrugated wheel. Several attempts, mainly experimental, to verify this have been made (see references [3] to [6]). There is a strong indication that the phenomena of hot spotting and roughness are related.…”