Abstract:
Tensile and Fatigue Crack Propagation (FCP) test have been carried
out on specimens of 7075 - T6 Aluminium alloy of two ranges of
thicknesses which are 10 mm. and 24 mm. Rates of fatigue crack propagation
vs. range of stress intensity factor (Al<) curves for this alloy
has been plotted. Axial - loads were used on 120 mm. wide CT (Compact
Tension) specimens. These tests were made at different stress ratios R
(ratio of the minimum stress to the maximum stress) ranging from 0.6
to 0.911 and at maximam stress levels ranging from 0.6 - 2.7 Ksi (4.1-
18.4 MN/nr2) to study the effects of stress ratio on fatigue crack growth.
The results were compared for both thicknesses. Finally, the da/dN versus
K data have been analysed and «best fit» straight lines for the graphs
computed by the least square method.