Characteristics of the brittle failure

Brittle fractures have certain characteristics that permit them to be properly identified:
  1. There is no gross permanent or plastic deformation of the metal in the region of brittle fracture, although there may be permanent deformation in other locations where relatively ductile fracture has occurred.
  2. The surface of a brittle fracture is perpendicular to the principal tensile stress. Thus the     direction of the tensile stress that caused the fracture to occur can be readily identified.
  3. Characteristic markings on the fracture surface frequently, but not always, point back to the location from which the fracture originated.
In the case of flat steel, such as sheet, plate, or flat bars, and also case-hardened regions, there are characteristic V-shaped "chevron" or "herringbone" marks that point toward the origin of the fracture. In many instances, these marks are extremely fine and very difficult to recognize unless a strong light is po sitioned so that it just grazes the projections of the surface texture.

Brittle fractures of extremely hard, fine-grain metals usually have little or no visible fracture pattern. In these cases, it may be very difficult to locate the origin with certainty.
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