The development of detector cars made possible the detection of many fissures before rail fracture had occurred, but it did not touch the problem of prevention of fissures. A "rolling-load" testing machine was designed and built which subjected a specimen of rail to repeated cycles of wheel load and bending moment. Before testing in this machine an etch test to detect the presence of shatter cracks was made on the rail from which the specimen was cut. Rolling-load tests showed the following results: Only shatter-cracked rails developed fissures, but not all shatter-cracked rails developed fissures. It is the complex stresses directly under a wheel load which cause cracks to develop into fissures. Bending moment tends to cause fissures to take a transverse direction, and accelerates their spread. No greater wheel load was required to start a fissure in a heavy rail than in a lighter rail. The minimum wheel load which started a fissure in the rolling-load tests was 40,000 lb. The wheel load necessary to start a fissure, the theoretical shearing stress in the zone where shatter cracks are located, the fatigue strength of rail steel, and the weakening effect of minute cracks (shown by fatigue tests of specimens) form a coherent picture of the mechanism of fissure formation and spread. The solution of the problem of preventing shatter cracks in rails was attacked by making tests of specimens from rails cooled in air and also controlled cooled. A large amount of study has been given to the problem of finding a nondestructive test which could be used to detect shatter cracks in new rails. Shatter cracks are so minute that changes, due to these shatter cracks, in properties or structure of metal around them, are masked by other variations in the metal. Unfinished work of the investigation relating to fissures includes formulation of proposed standards for control cooling of rails and for bend tests for acceptance of rails. Numerous photographs detail rail defects of the type described.

  • Corporate Authors:

    American Railway Engineering Association

    59 East Van Buren Street
    Chicago, IL  United States  60605
  • Authors:
    • Moore, H F
  • Publication Date: 1941

Media Info

  • Features: References;
  • Pagination: p. 681-751
  • Serial:
    • Volume: 42
    • Publisher: American Railway Engineering Association

Subject/Index Terms

Filing Info

  • Accession Number: 00033324
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jul 8 1994 12:00AM