Examination of Cracks in Wabco and Knorr Disc Brakes

On December 18, 198, three AMFLEET brake discs containing thermal cracks were surveyed at the AMTRAK wheel maintenance shops in Wilmington, DE. Two of these discs had been supplied by the Knorr Brake Corporation, and had belonged to the major fleet population. The third was one of approximately forty discs of a different design that had been supplied by the Westinghouse Air Brake Corporation (Wabco) for field testing. Parts were cut from the three discs and subsequently delivered to the Department of Materials Science and Engineering, Massachusetts Institute of Technology, for metallurgical evaluation. The Knorr and Wabco disc brakes were examined for the cause of cracking and why there is a difference in the type of cracks found in the two designs. Microstructure, microhardness, hardness, composition, and crack surfaces were investigated. Little difference was noted between the two materials. The crack surfaces had been worn and corroded, and neither the origins of cracks nor directions of crack growth could be accurately determined. To further assess the performance of the Westinghouse Air Brake Co. disc brake, the tangs that join the disc to the hub in this design were examined for microstructure, microhardness, composition, dimensionals, and visual evidence of wear. The data were compared to the design requirements furnished by the manufacturer. The connecting bolts were also examined for wear, debris, deformation, and/or cracks. The Wabco tangs and connecting bolts were found to meet the manufacturer's specifications. The tangs and connecting bolts showed no signs of wear, cracking, or deformation. The microstructure and microhardness of the tangs were found to be similar to the metal in the disc region.


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Project Memorandum
  • Features: Figures; Photos; References; Tables;
  • Pagination: 30p

Subject/Index Terms

Filing Info

  • Accession Number: 01641809
  • Record Type: Publication
  • Report/Paper Numbers: RR930-PM-79-23
  • Files: TRIS, ATRI, USDOT
  • Created Date: Jul 25 2017 6:52PM