THE EFFECT OF HIGH IMPACT WHEELS ON RAIL FAILURE

Abstract eng:
Rail is subject to repeated load cycles and wear. These load cycles can induce fatigue and rail failure. As rail failure is less predictable, wear is the desirable failure mode and factors influencing rail failure are carefully managed by railroads. In North America, static wheel loads are limited to a nominal maximum of 159 KN; however, wheel treads can develop rolling contact fatigue resulting in so-called high impact wheels (HIW) that, before removal, can introduce high impact loads on the rail in excess of 700 KN. Transportation Technology Center Inc. (TTCI) was tasked by the Association of American Railroads (AAR) to determine the effect of HIW on rail failure and ascertain whether more stringent removal criteria should be applied. TTCI conducted extended high frequency strain measurements at a WILD site and related the measured strains to the dynamic impact loads by the WILD site. These measurements supported analytical models developed to simulate defect growth and rail failure. Results of the analysis suggest that HIW have a minimal effect on rail failure because of:  High attenuation of the bending wave under impact due to the high damping in the track.  The low probability of repeated HIW cycles on specific elements within the rail. This paper describes the measurement and analysis process as well as the development of the models and the interpretation of resulting data and conclusions drawn.

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