FORMATION OF FATIGUE CRACKS IN RAILS

The rates of unlimited fatigue strength resisting flexion, traction-compression, and shearing, are, in the case of a perfect steel, linear functions of the resistance to fracture caused by traction, in the author's view. He provides diagrams showing these rates, as well as their variation in relation to the rail surface. He makes brief reference to the distribution of pressures in the rail, and explains the manner in which the rates of unlimited fatigue strength can be exceeded when the rail contains inclusions of slag, segregations, or concentrations of ferrite. He explains, in detail, the mechanism of the propagation of the oval flaw and concludes with a number of observations concerning the means of improving the resistance of rails.