In-service surface temperature measurement of tread braked wheels with a novel on-board infrared rugged device

Abstract

Temperatures reached on railway wheels tread during braking with composite blocks are responsible for extensive damage unknown when cast iron brake blocks were used. The accurate measurement of wheel tread temperature during braking becomes then fundamental to tune models to estimate thermomechanical damage due to the combined thermal and vertical/longitudinal actions at the wheel/rail contact especially in fully loaded conditions. This measurement is not trivial during service braking, as contact (sliding) thermocouples are not reliable in the long term and conventional infrared sensors in the wavelength range 8–14 μm are not suitable for bright steel surfaces. Moreover, thermal cameras with the correct parameters are expensive and too delicate to be installed even temporarily on a freight wagon bogie frame. A low-cost, non-contact measuring device based on a rugged single-spot pyrometer sensitive to the correct infrared emission wavelength (1.5–1.8 μm) was developed. The pyrometer is mounted on a motorized slider continuously spanning the tread surface for a practically unlimited time. The functionality of a prototype was checked during braking sessions on a homologated brake rig, tuning the actual wheel tread emissivity with the help of specific finite element thermal simulations. The device was then mounted on a Y25 bogie and in-service measurements were performed. The paper describes the development and calibration of the device, concluding with the results of the in-service tests.

Keywords

Tread braking / Freight wagons / Thermal loads / Pyrometer / Infrared sensor / Braking tests

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