Analysis of Cyclic Deformation Near the Crack Tip

Fatigue Crack Propagation Behaviour in the Hardness Heterogeneous Field (Part 3)

Abstract

The cyclic deformation behaviour near the crack tip in the yield stress heterogeneous field was investigated by cyclic elasto plastic analysis on F.E.M. model.
ΔOCTD obtained analytically had a certain linear relationship with experimental ΔCTOD. Crack tip coming near the soft-hard boundary, the increment of ΔCTOD was reduced. The distance from the soft-hard boundary to the point where the increment of ΔCTOD was beginning to be reduced was not related to the yield stress in the hard region.
By using the plastic region asymmetric parameter, the fatigue crack inclined angle was plotted on the same curve as experimental one.
ΔCTOD was related to the cyclic equivalent plastic strain range distribution in the vicinity of the fatigue crack tip.