Abstract: The fatigue crack growth rate of two-dimensional short cracks ( 2.2mm) and long cracks (Δa>6mm) were compared using CT type specimens in 8090 aluminium-lithium jalloys. It was found that the short cracks grew much faster than long cracks, and the applied stress intensity factor range for short cracks may-be much lower than the threshold for long cracks. The above differences are attributed to crack closure effects.The growth of physically short cracks can be rationalized with that for long cracks in terms of effective stress intensity factor range.

Key words: aluminium-lithium alloy, short crack, crack closure