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

Debond radius (mm)
100
90
80
70
60
a/b=1.1 a/b=1
90
0 27
50
45
90
72
50
40
40
0 500 1000 1500 2000 2500
0 500 1000 1500 2000 2500
Cycle
Cycle
(a)
(b)
Figure 4.21: Debond radius vs. cycle for sandwich panels with elliptical debond with an a/b
ratio of (a) a/b=1.1 and (b) a/b=1.
For debonded panels with a/b=1.1, the radius in locations along the debond front converges fast.
For the circular debond, due to similar energy release rate and phase angle in different locations
along the debond front, the debond shape does not change as the debond grows, and remains
circular. The number of simulation cycles and the computational efficiency of the simulations are
shown in Table 4.4. By exploiting the cycle jump method, an approximate 80% reduction in
computational time is achieved. Furthermore, it appears that despite using the same control
parameter, the number of simulated cycles is different for panels with different debond a/b ratio
because of different behaviour of the state variables (energy release rate and phase angle) for
each case.
Table 4.4: Number of jumped cycles and computational efficiency for the simulation of
debonded panels with the control parameter qG=q=4 for 2500 cycles.
a/b Number of simulated cycles R=Njumped/Ntotal
1.7 588 0.77
1.4 376 0.85
1.1 288 0.89
1 415 0.83
84
Debond radius (mm)
100
80
70
60