Fatigue and Fracture Toughness in the Rail Industry
Fatigue in metals caused by cyclic loading progressively damages a localized area of a structure, eventually leading to the formation of cracks. Once a crack is formed, it will grow with each application of load. The growth rate will depend on a variety of factors; the magnitude of the load, the length of the crack and the remaining portion of un-cracked material, and the geometry of the crack. The crack will continue to grow until it reaches a critical size, which occurs when the stress-intensity factor exceeds the material’s fracture toughness. At this point, the crack growth will very rapidly, and the structure may fracture completely.