The fatigue crack growth for narrow band Gaussian
spectrum loading in 6063 was investigated by Veers et al.
[6]. The crack growth rates were determined for constant
amplitude loading at stress ratio (R) of 0.09, 0.3, and 0.5, and
for a variable amplitude loading simulated to match a
narrow-band Gaussian spectrum. Crack opening stress levels
measured by this method during constant amplitude loading
are found different because of the different heat treatment.
The results have shown that the crack growth is from
intergranular to transgranular formation.
The growth rate of fatigue cracks in prestrain 6063 T6 Alalloy
under different stress ratio was studied by Kumar and
Garg [7]. It was observed that the growth rate of fatigue
crack in the prestrain material was more than that of asreceived
material. It was shown by crack opening displacement
measurements that crack closure occurred to a lesser
extent in prestrain material. Kumar and Garg discussed the
increase in yield strength for fatigue crack growth and they
found that the fatigue life decreased as the percentage of
prestrain increases.
The effect of different aging conditions, with different
chemical composition and dispersoid contents on fatigue
fracture behavior of Al±Mg±Si alloy, was conducted by
Jiang et al. [8]. It was found that the dispersoid phase could
alter the mode of fatigue fracture by the in¯uence on the
deformation uniformity of the alloy.
Fatigue analysis for typical materials including 6063 Alalloy
system used for vertical axis wind turbine blades was
investigated by Van Den Avyle and Sutherland [9]. Two
types of data were measured: (a) stress versus number of
cycles (S±N curve) and (b) fatigue crack growth rate. The S±
N experiment was conducted on 6063 extruded material
using 100 bend specimens cycled at ®ne alternating stress
amplitudes. The cyclic crack growth rates were measured
using three loading rates.
Considerable work on precipitation hardening has been
carried out. However, in the present investigation the effect
of time and temperature on the mechanical and fatigue
fracture behavior of the 6063 aluminium alloy was investigated.
In the precipitation heat treatment process, the alloy
was heated to 793 K and the solid solution formed at this
temperature is retained in super-saturated state by quenching
rapidly in cold blast of air or in water to avoid any precipitation
during quenching. Finally, the alloy was heattreated
and the mechanical properties such as tensile
strength, hardness, ductility and fatigue fracture behaviour
of the alloy were studied. The fractured surfaces of different
heat-treated specimens were analysed using scanning electron
microscope (