Material discontinuity taking place either intercrystalline (along the grain boundary) or transcrystalline (penetrating the crystallites).

Differentiation is made between forced failure (due to unidirectional stresses) and dynamic failure (due to fluctuating stresses). Moreover, fracture due to large-area plastic deformation is referred to as ductile failure and, fracture due to plastic deformation that is limited to the direct ambience of a notch or a crack is referred to as non-deformed brittle failure.

Fig. 1 shows SEM images of an intercrystalline failure and Fig. 2 of a transcrystalline failure. A forced failure is illustrated in Fig. 3 and a ductile failure in Fig. 4.


  • Fig. 1: SEM images of an intercrystalline failure, 1000:1
  • Fig. 2:  SEM images of a transcrystalline failure, 1000:1
  • Fig. 3: Impact failure with RT in steel C 75N, heat-treated, 3000:1
  • Fig. 4: Section of a fatigue failure of steel   C 75N, stressing of a railway tie, 3000:1