Tangential bond stiffness evaluation of adhesive lap joints by spectral interference of the low-frequency A0 Lamb wave

Considering the influence of Lamb wave dispersion on the precision of damage detection, a new detection method of scattering source based on time-frequency curves and ellipse localization method is proposed. Empirical mode decomposition(EMD) is used to decompose the scattering signal into finite narrowband signals, and a modified continuous wavelet transform(CWT) is further used to get the time-frequency distribution(TFD) of the detected signal, and the arriving time of different frequency component is estimated based on TFD. A series of location results can be obtained from different frequency components using ellipse localization method. The damage position can finally be estimated by synthesizing localization results at different frequencies. Experiments on aluminum plate are conducted to demonstrate the efficiency of the proposed method. EMD-CWT analysis can get precise time-frequency curves in highly dispersive low frequency band of A0 mode. The damage location results is more accurate and the influence from occasional factors can be suppressed by using the synthesized method.

Download Full-text

Clamping Resonators for Low-Frequency S0 Lamb Wave Reflection

Applied Sciences ◽

10.3390/app9020257 ◽

2019 ◽

Vol 9 (2) ◽

pp. 257 ◽

Cited By ~ 1

Author(s):

Christopher Hakoda ◽

Cliff Lissenden ◽

Parisa Shokouhi

Keyword(s):

Band Gap ◽

Lamb Wave ◽

Wave Reflection ◽

Stop Band ◽

Low Frequency ◽

Wave Mode ◽

Design Concept ◽

The Other ◽

Transmitted Signal ◽

Wave Modes

A recent elastic metamaterial study found that resonators that “clamp” a plate waveguide can be used to create a frequency stop-band gap. The result was that the resonator array can prohibit the propagation of an A0 Lamb wave mode. This study investigates whether the concept can be extended to S0 Lamb wave modes by designing resonators that can prohibit the propagation of S0 Lamb wave modes in a 1-mm aluminum plate waveguide at 50 kHz. The frequency-matched resonators did not reduce the transmitted signal, leading to the conclusion that the design concept of frequency-matched resonators is not always effective. On the other hand, the resonators designed to clamp the upper surface of the plate were very effective and reduced the transmitted signal by approximately 75%.

Download Full-text

Extremely low-frequency Lamb wave band gaps in a sandwich phononic crystal thin plate

International Journal of Modern Physics B ◽

10.1142/s0217979215500277 ◽

2015 ◽

Vol 29 (05) ◽

pp. 1550027 ◽

Cited By ~ 11

Author(s):

Li Shen ◽

Jiu Hui Wu ◽

Zhangyi Liu ◽

Gang Fu

Keyword(s):

Lamb Wave ◽

Vector Fields ◽

Displacement Vector ◽

Phononic Crystal ◽

Lower Boundary ◽

Low Frequency ◽

Sound Insulation ◽

Geometrical Parameters ◽

Wave Band ◽

Reduction Effect

In this paper, a kind of sandwich phononic crystal (PC) plate with silicon rubber scatterers embedded in polymethyl methacrylate (PMMA) matrix is proposed to demonstrate its low-frequency Lamb wave band gap (BG) characteristics. The dispersion relationship and the displacement vector fields of the basic slab modes and the locally resonant modes are investigated to show the BG formation mechanism. The anti-symmetric Lamb wave BG is further studied due to its important function in reducing vibration. The analysis on the BG characteristics of the PC through changing their geometrical parameters is performed. By optimizing the structure, a sandwich PC plate with a thickness of only 3 mm and a lower boundary (as low as 23.9 Hz) of the first anti-symmetric BG is designed. Finally, sound insulation experiment on a sandwich PC plate with the thickness of only 2.5 mm is conducted, showing satisfactory noise reduction effect in the frequency range of the anti-symmetric Lamb BG. Therefore, this kind of sandwich PC plate has potential applications in controlling vibration and noise in low-frequency ranges.

Download Full-text