Rolling Contact Fatigue Measurement

Causes and Impact of Rolling Contact Fatigue

Rolling Contact Fatigue (RCF) defects (including head checks, squats, gauge corner cracking, and shelling) are one of the major drivers behind rail maintenance and replacement in freight, commuter and light rail transit systems, and can be linked to upwards of 100 derailments every year in North America.

RCF develops at the wheel-rail interface due to the high stress contact patch between the wheel and the rail and the resulting ratcheting of the surface to the point of failure. A number of factors can increase the likelihood of RCF developing:

+ Poor traction conditions during acceleration and breaking

+ Wet environments as well as alternating wet and dry environments

+ Metallurgical issues related to fatigue properties, hardness and wear resistance

+ Tight curves as well as geometry defects including tight gauge, poor alignment and cant errors

Once RCF develops, it will continue to grow and worsen leading to poor ride quality, accelerated wear and tear on track and rolling stock, and increased derailment risk due to rail breaks and wheel climbs.

Early detection of RCF is crucial to reducing maintenance costs (by reducing the required depth of grinding) as well as derailment risk. However, visual inspection is insufficient as RCF defects initiate and grow long before they’re visible to the naked eye.

While Ultrasonic inspection is well-suited to the internal inspection of rails, RCF forms at (or very near) the surface of rails and is typically not well detected, nor well characterized, by ultrasonic methods.

Conversely, Eddy Current technology provides a highly sensitive and reliable method for detecting and quantifying surface and near surface defects. Eddy current inspections work by inducing small, circulating electrical currents (eddy currents) to flow in the rail which are disrupted when defects are encountered; providing a signal to determine the location, size and orientation of RCF defects.

The Right Configuration for your Application

We offer a variety of Eddy Current-based measurement tools for RCF measurement in rails and frogs ranging from simple hand-held units suitable for spot checks, to trolleys for extended measuring projects, and even self-propelled measuring carts designed for large-scale surveys.

+ HCscan HD – a compact, handheld device for RCF measurement with a depth resolution of 0.01mm

+ HCscan – a compact, handheld device for RCF measurement with a depth resolution of 0.1mm

+ GF-04E Trolley – a 4 channel inspection trolley designed to inspect one rail at a time. The trolley supports 20 different positions for probe deployment to enable scanning of the entire rail-wheel interface

+ GF-08E Trolley – an 8 channel inspection trolley designed to inspect both rails simultaneously (4 probes per rail). The trolley supports 20 different positions for probe deployment on each rail

+ GF-20 Trolley – a 20 channel inspection trolley designed to inspect both rails simultaneously with an array of 10 probes per rail to provide measurement across the entire wheel rail interface

+ GFD-08 – an 8 channel measurement system (4 probes per rail) deployed on a self-propelled cart. The trolley supports 20 different positions for probe deployment on each rail

+ GFS-08 – an 8 channel measurement system (4 probes per rail) deployed designed to be installed on rolling stock

Measurement Capabilities

Cracks as small as 0.1mm can be detected and crack length, angle and depth reported. Hand-held devices feature integrated displays designed to make defect detection and evaluation simple and efficient. Trolley and cart based systems provide extended data viewing and reporting capabilities through connected tablets and laptop devices.