Directional stability of an originally straight crack

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The directional stability of an originally straight crack under symmetric remote loading is studied after introduction of an infinitesimal disturbance at one or both tips of the crack. The crack is assumed to grow slowly under vanishing mode II stress intensity factor. Directional stability is defined to prevail if the angle formed by the straight line between the crack tips and the original crack direction eventually decreases during crack growth. This is shown to be the case if, and only if, the principal stress perpendicular to the original crack is the largest of the two in-plane stresses.
Another candidate for definition of directional stability is also discussed, even though it appears less logical, since it concentrates on the position of the crack tips rather than on the main direction of the crack. It assumes that directional stability prevails if the crack tips eventually move closer toward the line along the original crack. This definition leads to directional instability when the principal stress in the original crack direction is larger than the fraction 1-/4 of the other in-plane stress.
Original languageEnglish
Pages (from-to)121-128
JournalInternational Journal of Fracture
Issue number2
Publication statusPublished - 1992

Subject classification (UKÄ)

  • Applied Mechanics
  • Engineering and Technology


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