Non-propagation Of Fatigue Cracks Research Articles

On the Frost-Dugdale plot for non-propagating cracks

The Frost–Dugdale plot is re-examined and the subject of the non-propagation of fatigue cracks is updated to emphasize that fatigue crack closure is the principal factor responsible for the non-propagation of fatigue cracks which originate at notches. The limitations of the original Frost–Dugdale plot with respect to notch depth are also discussed.

Initiation and Growth of Intralaminar Fatigue Cracks in Notched Unidirectional CFRP.

The initiation and growth of intralaminar fatigue cracks in notched unidirectional carbon/epoxy laminates, Toray T800H/#3631, were investigated under tension-tension cyclic loading with constant stress amplitudes. The initiation of fatigue cracks at the notch root was caused by shear stress concentration. The fatigue life for crack initiation was a unique function of the maximum shear stress divided by the critical value of the maximum shear stress for static tensile fracture. Fatigue cracks propagated under mixed mode, mode I and mode II. When the crack length was short, the crack propagation rate was determined by the mode I stress intensity range, ΔKI. As the crack length increased, the mode II stress intensity range, ΔKII, became a dominant crack-driving force. Although the ΔKI value increased with crack length, the propagation rate monotonically decreased and the crack finally stopped. Such deceleration and non propagation of cracks were caused by the increase of interlocking and friction between fracture surfaces. The condition of the non propagation of fatigue cracks was determined by a constant value of ΔKI for short cracks in the ΔKI-dominant region. 0n the other hand, for long cracks in the ΔKII-dominant region, the threshold value of ΔKII increased with increasing crack length.

The Effects of Notch Depth on the Initiation Propagation and Non-propagation of Fatigue Cracks

The Effects of Notch Depth on the Initiation Propagation and Non-propagation of Fatigue Cracks