A study of the crack wake closure/opening behaviour of short fatigue cracks and its influence on crack growth

作者：Zhang XP^*; Wang CH; Ye L; Mai YW

来源：Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing, 2005, 406(1-2): 195-204.

DOI：10.1016/j.msea.2005.06.034

• short fatigue cracks
• crack closure
• crack growth
• in situ SEM fatigue

Crack closure behaviour has long been found to have a significant influence on fatigue crack growth and a large amount of research has been done in the past 3 decades. Whereas the majority of these research efforts focus on long cracks, relatively little is known for short fatigue cracks, in particular for microstructurally short cracks. This paper presents a quantitative characterisation of the wake closure/opening behaviour of microstructurally short fatigue cracks under cyclic loading for a structural aluminium alloy 2024-T351 using an in situ SEM fatigue testing system. The results clearly indicate that crack closure level was at a peak value at crack lengths of similar to 100-150 mu m. Beyond the regime of short crack growth, the crack closure stress decreases gradually with crack length, approaching asymptotically to a constant value at crack lengths of about 1.5 mm. In addition, it was found that the crack closure/opening stress intensity factor, K(cl) (K(op)), is nearly constant while the maximum stress intensity factor increases with crack size. Therefore, the effect of crack closure is most significant in the early stage of short fatigue crack propagation. The experimental results have also been compared with those predicted by Newman's model and a model previously developed by the authors.

• 出版日期2005-10-15
• 单位华南理工大学