Equivalentní K-faktor pro šíření únavových trhlin v prahové oblasti v módu II+III v ARMCO železe

Equivalent K-factor for Near-threshold Mode II+III Fatigue Crack Growth in ARMCO Iron

abstract

en

The research was focused on the near-threshold fatigue crack propagation under mixed-mode II+III in the ARMCO iron. The aim was to evaluate selected mixed-mode criteria to find a suitable description of the mixed-mode crack propagation. The data were taken from experiments on cylindrical bars with circumferential cracked notch loaded in shear. The crack was loaded by various combination of modes II and III. The dependences of stress intensity factors (SIFs) in mode II and III on the position on the specimen cross section and on the precrack length were numerically calculated using FEM. Because of the crack closure effect, the effective SIF was dependent on the crack extension. For sorting out the mixed-mode data, simple criteria were proposed and analyzed. All these criteria are normalized to 1 when approaching the mixed-mode threshold.

The research was focused on the near-threshold fatigue crack propagation under mixed-mode II+III in the ARMCO iron. The aim was to evaluate selected mixed-mode criteria to find a suitable description of the mixed-mode crack propagation. The data were taken from experiments on cylindrical bars with circumferential cracked notch loaded in shear. The crack was loaded by various combination of modes II and III. The dependences of stress intensity factors (SIFs) in mode II and III on the position on the specimen cross section and on the precrack length were numerically calculated using FEM. Because of the crack closure effect, the effective SIF was dependent on the crack extension. For sorting out the mixed-mode data, simple criteria were proposed and analyzed. All these criteria are normalized to 1 when approaching the mixed-mode threshold.

The research was focused on the near-threshold fatigue crack propagation under mixed-mode II+III in the ARMCO iron. The aim was to evaluate selected mixed-mode criteria to find a suitable description of the mixed-mode crack propagation. The data were taken from experiments on cylindrical bars with circumferential cracked notch loaded in shear. The crack was loaded by various combination of modes II and III. The dependences of stress intensity factors (SIFs) in mode II and III on the position on the specimen cross section and on the precrack length were numerically calculated using FEM. Because of the crack closure effect, the effective SIF was dependent on the crack extension. For sorting out the mixed-mode data, simple criteria were proposed and analyzed. All these criteria are normalized to 1 when approaching the mixed-mode threshold.

mode II+III, crack growth threshold, mixed-mode criteria, ARMCO iron

mode II+III, crack growth threshold, mixed-mode criteria, ARMCO iron

02.04.2012

Oxford