Characterization of dislocation structures around a mixed-mode fatigue crack tip in a single-crystalline iron–silicon alloy

The trajectory of fatigue crack growth is influenced by many parameters and can be irregular due to changes in stress distribution or in material properties as the crack progresses. Images of the surface of a standardized test specimen can be used to visualize the crack trajectory in a non-destructive way. Accurately identifying the location of the crack tip, however, is challenging and requires devoted image postprocessing. In this respect, digital image correlation allows to obtain full field displacement and strain fields by analysing changes of digital images of the same sample at different stages of loading. This information can be used for the purpose of crack tip tracking. This paper presents a combined experimental-numerical study of detection and prediction of fatigue crack propagation path by means of digital image correlation (DIC) and the extended finite element method (X-FEM). Experimental validation and analyses are carried out on a modified C(T) specimen in which a curved crack trajectory is triggered by introducing mixed-mode (tension + shear) loading. The developed tools are used for validating an automated framework for crack propagation prediction.

Download Full-text

On the micromechanism of hydrogen-assisted cracking in a single-crystalline iron–silicon alloy thin sheet

Scripta Materialia ◽

10.1016/j.scriptamat.2010.11.035 ◽

2011 ◽

Vol 64 (6) ◽

pp. 537-540 ◽

Cited By ~ 9

Author(s):

Yoshimasa Takahashi ◽

Keigo Yamaguchi ◽

Masaki Tanaka ◽

Kenji Higashida ◽

Hiroshi Noguchi

Keyword(s):

Thin Sheet ◽

Single Crystalline ◽

Silicon Alloy ◽

Iron Silicon ◽

Hydrogen Assisted Cracking

Download Full-text

The Characteristics of Propagation for Mixed-Mode Fatigue Crack under Stress Re-Distribution at Fatigue Crack Tip

International Journal of Modern Physics B ◽

10.1142/s0217979203019885 ◽

2003 ◽

Vol 17 (08n09) ◽

pp. 1922-1927 ◽

Cited By ~ 1

Author(s):

Sam Hong Song ◽

Jeong Moo Lee

Keyword(s):

Fatigue Crack ◽

Crack Propagation ◽

Fatigue Crack Propagation ◽

Mixed Mode ◽

Applied Load ◽

Crack Tip ◽

Crack Propagation Rate ◽

Propagation Rate ◽

Stress Redistribution ◽

Fatigue Crack Propagation Rate

The practical condition of applied load represents mixed-mode loading condition due to complications of element geometry and applied load. Also, the characteristics of fatigue crack propagation under mixed mode were affected by constrained shape of structures and applied load variation. There are continuous variations of stress condition at crack tip on the fatigue crack during propagation. Therefore, it is necessary to investigate the propagation behavior of mixed-mode fatigue crack under stress redistribution condition. We established the experimental method in order to form the stress redistribution condition. It is assumed that the stress around the crack tip under mixed-mode fatigue loading is redistributed. This test consisted of the 1st and the 2nd round of tests. The stress re distribution was formed by changing the loading direction at propagating mixed-mode fatigue crack tip. In this study, the behavior of mixed-mode fatigue crack affected by stress redistribution was investigated by comparing fatigue crack propagation rate, fatigue crack propagation paths and fatigue crack branch angle. From the experiment, as loading application angle and thickness change, the fatigue crack propagation rate and angle under mixed mode were affected by stress redistribution.

Download Full-text