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1 Zeszyty Naukowe. Mechanika / Politechnika Opolska

1 2005

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Dislocation distribution in the plastic zone and growth of a short fatigue crack

Bjerkén C., Melin S.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

2005

z. 82

29-36

The growth of a short edge crack under fatigue loading is investigated in detail for more than 11 000 cycles. The developing local plasticity consists of discrete dislocations that are emitted from the crack tip. The edge crack is modelled by a distribution of dislocation dipoles. The competition between global loading and local shielding of the crack tip governs the crack growth. The material modelled is BCC iron and the load is varied with a stress ratio R=-1. The growth rate increases in discrete steps with short periods of retardation from approx. The size of Burgers vector, b, per cycle up to 17 b. The plastic zone changes from having an elongating slender form to include a low-angle boundary.