Residual Strength and Fatigue Lifetime of ... - Solid Mechanics
Residual Strength and Fatigue Lifetime of ... - Solid Mechanics Residual Strength and Fatigue Lifetime of ... - Solid Mechanics
Figure 5.42: Zero and ninety degrees positions along the debond front. Initial crack 0 debond section Initial crack 90 debond section Crack growth path Crack growth path Figure 5.43: Fatigue crack growth paths in the tested sandwich panels. 5.3.2 Finite Element Modelling of the Debonded Panels A 3D finite element model of the debonded panels is developed in the commercial finite element code ANSYS. 8-node iso-parametric elements (PLANE45) are exploited for finite element modelling. Because of geometrical and loading symmetry only a quarter of the panel is 120 90 0
generated. Symmetry boundary conditions are imposed in the symmetry planes. The edges of the panels are clamped by imposing a zero displacement boundary condition. The finite element model of the debonded panel is shown in Figure 5.44. The accelerated fatigue crack growth simulation scheme (cycle jump method) developed in the previous chapter is used to simulate fatigue crack propagation in the sandwich panels. The energy release rate and mode-mixity phase angle are chosen as state variables in the cycle jump scheme. Figure 5.45 illustrates the distribution of the energy release rate and the related mode-mixity phase angle during the first cycle along the debond front using the maximum fatigue load amplitude. As expected the energy release rate and mode-mixity phase angle are evenly distributed along the debond front because of the circular shape of the debond and the large distance to the panel boundaries. Figure 5.46 shows the energy release rate and mode-mixity phase angle vs. debond diameter using the maximum fatigue load amplitude. Debond Figure 5.44: Quarter finite element model of the debonded panels with a circular debond. The smallest element size is 10m. 121 Clamp B. C. Symmetry B. C. 310 mm x y
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Figure 5.42: Zero <strong>and</strong> ninety degrees positions along the debond front.<br />
Initial crack<br />
0 debond section<br />
Initial crack<br />
90 debond section<br />
Crack growth path<br />
Crack growth path<br />
Figure 5.43: <strong>Fatigue</strong> crack growth paths in the tested s<strong>and</strong>wich panels.<br />
5.3.2 Finite Element Modelling <strong>of</strong> the Debonded Panels<br />
A 3D finite element model <strong>of</strong> the debonded panels is developed in the commercial finite element<br />
code ANSYS. 8-node iso-parametric elements (PLANE45) are exploited for finite element<br />
modelling. Because <strong>of</strong> geometrical <strong>and</strong> loading symmetry only a quarter <strong>of</strong> the panel is<br />
120<br />
90<br />
0
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