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In order to investigate the influence of parameter variation and three‑dimensional effect on the interaction between conical shock wave and plate boundary layer， Menter‑SST two‑equation turbulence model is used to simulate the interaction between three‑dimensional conical shock wave and plate boundary layer in a supersonic Mach 2 flow， and the results are analyzed qualitatively and quantitatively. The influence caused by the change of shock‑wave generator’s half‑cone angle and Reynolds number on the flow in the interference region is studied， and the variation rules of flow separation caused by parameter variation are summarized. Moreover， the two‑dimensional cases which are equivalent to the incident shock wave on the central symmetry plane in corresponding three‑dimensional cases are also calculated， and the results are compared with the three‑dimensional cases. The comparison shows that the interference between conical shock wave and plate boundary layer is obviously different from that of two‑dimensional cases in terms of wall pressure coefficient， separation vortex， vorticity distribution and so on. [ABSTRACT FROM AUTHOR]

In Lamb wave damage imaging of complicated aircraft structures, the signal wave packets can be easily elongated and deformed due to the dispersion of Lamb wave. The signal resolution is then degraded and the final damage imaging results could be affected. Lamb wave dispersion compensation has become an issue needing to be resolved immediately. However, the traditional dispersion compensation methods usually require the theoretically-calculated dispersion curves of Lamb waves and are hard to be applied in complicated aircraft structures. In this paper, with in-situ measured relative wavenumber curves, the compensation process of linearly-dispersive signal construction (LDSC) is performed to solve the difficult problem of dispersion removal of Lamb waves in complicated aircraft structures. Hereafter, LDSC is used in delay-and-sum imaging to realize high resolution damage imaging, during which the quasi-wideband excitation waveform of 1.5-cycle sine burst is introduced to reduce the influence of complicated aircraft structures. Finally, the proposed methods are verified by the experiment on the actual complicated aircraft beam. [ABSTRACT FROM AUTHOR]

To further increase the computational efficiency of the time domain spectral finite element method for modeling Lamb wave propagation in plate-like structures, a novel Z-D spectral plate element is proposed which can model the 3-D behavior of Lamb wave propagations. The nodal distribution of the element possesses Lebesgue optimal property and the extended displacement field is adopted in the formulations. Each node has 6 degrees of freedom. The diagonal mass matrix is obtained by using a simple method, equivalent to the row summation of a consistent mass matrix. Results reveal that the proposed spectral plate element has similar behavior as the two widely used spectral elements. Moreover, its computational efficiency is raised due to smaller effort in formulation of the mass matrix, larger critical time step and the ability to model the 3-D behavior of Lamb wave propagation in plates. [ABSTRACT FROM AUTHOR]

Based on Timoshenko beam theory, dispersion relation of Lamb wave in composite laminated beam with different plies is analyzed. Wave reflection and transmission are studied at the joint of a non-uniform composite laminated beam and at the tip of the delamination in a composite laminated beam containing semi-infinite delamination. It is found that Lamb wave modes are coupled with and converted to each other in composite laminated beams. Based upon time-reversion theory, Stokes relations between reflection and transmission in the above two models are proposed. Compared with the method in the reference, wave propagation in a beam structure by simulation verifies the proposed theory resolution. [ABSTRACT FROM AUTHOR]