Crack Tip Plastic Strain Research Articles

Fatigue crack propagation rate and the crack tip plastic strain amplitude in polycrystalline copper

The size of the dislocation cells produced by deformation at the fatigue crack tip in copper specimens was used as a measure of the crack tip stress amplitude. Using the cyclic stress-strain curve, the values of the crack tip plastic strain amplitude and their dependence on the macroscopic stress intensity factor were obtained. While the fatigue crack propagation rate expressed as a function of the stress intensity factor is strongly influenced by the testing temperature and frequency, it is almost independent of these parameters when expressed in terms of the crack tip plastic strain amplitude. The results of a finite element computation led to the same conclusion.

Study of the crack tip plastic strain in a nickel-based superalloy

Selected area channeling patterns (SACPs) of high quality have been obtained from a single crystal nickel-based superalloy, and the effect of plastic strain upon the patterns has been analyzed. Analysis of the pattern quality enables strains of approximately 1% to be readily detected, thus permitting the mapping of a crack tip plastic zone associated with a fatigue crack. A systematic deterioration in SACP quality with strain has also been demonstrated and the technique applied to the determination of the strain distribution within the plastic zone.

Significance of crack opening displacement and crack tip plastic strain energy in fracture initiation

AbstractThe development of an intense strain region, formed locally at a blunting crack tip, and the equivalent plastic strain distribution within it were investigated in terms of crack opening displacement δt by means of the recrystallization technique. The results obtained showed that the equivalent plastic strain within the region was given by e ¯ p = e ¯ 0 ( δ t cos θ r ′ ) m <mm...