Rolling Contact Fatigue

Client Type: Main line operator

Objective

To conduct a track site monitoring programme in order to develop greater understanding of the development of rolling contact fatigue (RCF) cracking both in terms of causative factors and propagation rates.

Approach

Corus undertook a comprehensive rail monitoring programme over a four year period.  It comprised regular monitoring visits to a range of sites and involved a variety of track types.  Rails exhibiting signs of RCF development were removed from track and subjected to a number of metallurgical investigations.

Method

In order to ensure the validity of the monitoring results it was necessary to devise a strict programme methodology.  It comprised:

• Identification of an 18m length of track within each site for detailed monitoring.
• Measurement of a range of features within the selected track length.  These included cant, gauge, rail head profile, running band width and railhead hardness.  Ultrasonic and eddy current testing were used as apprpriate.  Assessments were also made of the severity and location of RCF cracking.
• Observation of an extended length of the site to enable assessment of specific track features including wet beds, corrugations and sleeper types.

Each site was visited three or four times over the course of a year to allow accurate assessment of the rate of defect propagation and identification of any change in track features and geometry.

Subsequent metallurgical examinations were carried out with the aim of accurately confirming the depth and extent of defects.   The samples were either sectioned or broken open (as appropriate) for RCF crack measurement.

Deliverables

Over four years, Corus delivered a comprehensive and practical understanding of the rate and characteristics of RCF development to its client.  The Corus team produced recommendations for effective and efficient corrective actions based on practical observations combined with knowledge of non-destructive testing techniques and theoretical analysis of defect initiation and propagation.