Residual Strength and Fatigue Lifetime of ... - Solid Mechanics

As described before in Equations (4.11)-(4.13) the number of jumped cycles, the computational
efficiency, the average relative error, for the debond growth for simulations with different
control parameters are listed in Table 4.3. It is seen that by increasing the control parameter, the
number of simulated cycles decreases significantly, but the accuracy of the simulation decreases
as well. Nevertheless, the average error in the evaluation of the debond length is less than 0.1%
for all control parameters. It should be noted that for qG=q=4 with a good accuracy and by use
of the cycle jump method, only 145 cycles are required for the simulation of 500 cycles, which
results in a 71% reduction in the computational time.
Table 4.3: Number of jumped cycles, computational efficiency and average relative error for
the debond length.
Control parameter
qG=q
Number of
simulated cycles
Number of jumps
occurred
83
R
Average relative error
of crack length (%)
1 303 16 0.39 0.03
2.5 171 17 0.66 0.05
4 145 15 0.71 0.08
Fatigue debond growth is simulated for 2500 cycles using the control parameter qG=q=4 and
the a/b ratio of 1.7, 1.4, 1.1 and 1. Figures 4.20 and 4.21 show the debond radius in different
crack front locations along the debond. During the initial cycles, the debond growth is small in
the proximity of the large radius of the ellipse, but as the debond propagates the radius at
different points along the debond front converges, which leads to a change in the debond shape
from ellipse to circle.
Debond radius (mm)
100
90
80
70
60
50
a/b=1.7 a/b=1.4
90
0 27
45 72
90
40
40
0 500 1000 1500 2000 2500
0 500 1000 1500 2000 2500
Cycle
Cycle
(a)
(b)
Figure 4.20: Debond radius vs. cycle for sandwich panels with elliptical debond with an a/b
ratio of (a) a/b=1.7 and (b) a/b=1.4.
Debond radius (mm)
100
80
70
60
50
0 27
45 72
90