Mode conversions under these damaged conditions were examined numerically. Damage was modeled in the form of a notch in the core section to simulate a cracked core, and delamination was modeled between the spar and core material to simulate spar-core disbond. Dispersion of Rayleigh waves in multi-layered half-space was also explored.
Numerical simulations showed that a Lamb wave excited in the spar section of the blade gets converted into Rayleigh wave which travels across the spar-core section and mode converts back into Lamb wave. To understand the various mode conversions, finite element models of a generalized helicopter rotor blade were created and subjected to transient analysis using a commercial finite element code ANSYS. Wave propagation in such structures deviate from the generic Lamb wave propagation in sandwich panels. In particular, this research focuses on structures which employ high stiffness, high density core materials. This paper extends the work presented earlier on inspection of helicopter rotor blades using guided Lamb modes by focusing on inspecting the spar-core bond.
0 kommentar(er)
