Modelling of Tortuous Crack Fronts in Shear Loading Mode

abstrakt

en

The contribution is related to experiments on near-threshold fatigue cracks under shear modes II, III and II+III in bcc metals. Cylindrical bars with circumferential cracked notch were loaded by shear force. The notch is located in the cross-section where no bending moment is present and it is loaded in pure shear. In-plane pre-cracks with microtortuous crack front were created by compressive cyclic loading in mode I to obtain smooth fracture surfaces and, consequently, the effective values of crack driving force could be measured. The circumferential pre-crack front could be modelled as a serrated front of a linear roughness identical to the real one. As reported elsewhere, the fatigue crack in bcc metals loaded under shear modes II, III and II+III always grows by creation and coalescence of local tongues loaded in mode II. Therefore, the aim of the model was to calculate the local stress intensity factor k 2 as a driving force for fatigue crack initiation and growth along the whole serrated crack front.

The contribution is related to experiments on near-threshold fatigue cracks under shear modes II, III and II+III in bcc metals. Cylindrical bars with circumferential cracked notch were loaded by shear force. The notch is located in the cross-section where no bending moment is present and it is loaded in pure shear. In-plane pre-cracks with microtortuous crack front were created by compressive cyclic loading in mode I to obtain smooth fracture surfaces and, consequently, the effective values of crack driving force could be measured. The circumferential pre-crack front could be modelled as a serrated front of a linear roughness identical to the real one. As reported elsewhere, the fatigue crack in bcc metals loaded under shear modes II, III and II+III always grows by creation and coalescence of local tongues loaded in mode II. Therefore, the aim of the model was to calculate the local stress intensity factor k 2 as a driving force for fatigue crack initiation and growth along the whole serrated crack front.

shear modes, stress intensity factors, serrated crack front, fatigue crack growth, local mode II

15.12.2017

X-Academy

Kuala Lumpur

Proceedings of 5th International Conference on Mechanical Engineering, Materials Science and Civil Engineering

14–15

2