Acoustic Scattering from Bi-Layered Cylindrical Shells: Influence of the Layers Thicknesses on the Guided Waves

2019 ◽  
Vol 105 (6) ◽  
pp. 1251-1257
Author(s):  
Younes Khandouch ◽  
El Houcein Aassif ◽  
Said Agounad
Keyword(s):  
Stainless Steel ◽  
Guided Waves ◽  
Shape Change ◽  
Cylindrical Shells ◽  
Acoustic Scattering ◽  
Modal Identification ◽  
Current Work ◽  
Geometrical Characteristics ◽  
Cutoff Frequencies

The current work focuses on the study of acoustic scattering from bi-layered stainless steel-copper and copper-stainless steel cylindrical shells filled with air and immersed in water. This paper is interested in revealing the effects of physical and geometrical characteristics of the layers constituting the shells on the scattering phenomenon. The object of this work, is to study the influence of the layers thicknesses on guided waves, the overall thickness of the shells is fixed. The plane of modal identification was chosen to analyze the scattering phenomenon. We investigate the resonance trajectories of the guided waves, especially the curves change. The investigation and comparison made on resonance trajectories, show a shape change, a gradual deviation, or both, appear on the resonance trajectories of different guided waves, for the reduced cutoff frequencies of guided waves a sliding to higher and lower value are noticed. The interaction between guided waves is also manifested in the scattering phenomenon. The findings for the bi-layered cylindrical shells are then compared with those obtained for the mono-layered stainless steel and copper cylindrical shells. Then, this work is completed by an investigation on the reduced cut-off frequencies of the A1 wave, that have been extracted for different possible values of the intermediary radius. In this part, to understand the observed phenomena, other examples of bi-layered cylindrical shells are introduced. The obtained results are analyzed and investigated.

Acoustic scattering from cylindrical shells: Guided waves and resonances of the liquid column

Ultrasonics ◽  
1986 ◽  
Vol 24 (6) ◽  
pp. 354-362 ◽  
Author(s):  
G. Maze ◽  
J.L. Izbicki ◽  
J. Ripoche
Keyword(s):  
Guided Waves ◽  
Cylindrical Shells ◽  
Acoustic Scattering ◽  
Liquid Column

scholarly journals An Experimental Study on the Shape Changes of TiO2Nanocrystals Synthesized by Microemulsion-Solvothermal Method

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Wei Kong ◽  
Bo Liu ◽  
Bo Ye ◽  
Zhongping Yu ◽  
Hua Wang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Stainless Steel ◽  
Oleic Acid ◽  
Solvothermal Method ◽  
Shape Change ◽  
Tetrabutyl Titanate ◽  
Microemulsion System ◽  
Solvothermal Process ◽  
Shape Changes ◽  
Shape And Size

Titanium dioxide (TiO2) nanocrystals of different shape were successfully synthesized in a new microemulsion system through a solvothermal process. The TiO2nanocrystals were prepared from the reaction of tetrabutyl titanate (TBT),H2O, and oleic acid (OA), which were used as solvent and surfactant at 300∘Cand 240∘Cin a stainless steel autoclave. The sphere, polygon, and rhombus-shaped nanocrystals have been prepared at 300∘Cand the dot- and- rod shaped nanocrystals have been synthesized at 240∘C. The effect of the reaction time on the shape and size of TiO2nanocrystals in this method was studied in the present paper. The size distribution of TiO2nanocrystals prepared at 300∘Cfor different hours is also studied. In addition, an attempt to describe the mechanism of shape change of TiO2nanocrystals was presented in this paper.

scholarly journals Research on a Rail Defect Location Method Based on a Single Mode Extraction Algorithm

2019 ◽  
Vol 9 (6) ◽  
pp. 1107 ◽  
Author(s):  
Bo Xing ◽  
Zujun Yu ◽  
Xining Xu ◽  
Liqiang Zhu ◽  
Hongmei Shi
Keyword(s):  
Finite Element ◽  
Guided Waves ◽  
Single Mode ◽  
Dispersion Curves ◽  
Modal Identification ◽  
Propagation Time ◽  
Location Method ◽  
Defect Location ◽  
Extraction Algorithm ◽  
Mode Extraction

This paper proposes a rail defect location method based on a single mode extraction algorithm (SMEA) of ultrasonic guided waves. Simulation analysis and verification were conducted. The dispersion curves of a CHN60 rail were obtained using the semi-analytical finite element method, and the modal data of the guided waves were determined. According to the inverse transformation of the excitation response algorithm, modal identification under low-frequency and high-frequency excitation was realized, and the vibration displacements at other positions of a rail were successfully predicted. Furthermore, an SMEA for guided waves is proposed, through which the single extraction results of four modes were successfully obtained when the rail was excited along different excitation directions at a frequency of 200 Hz. In addition, the SMEA was applied to defect location detection, and the single reflection mode waveform of the defect was extracted. Based on the group velocity of the mode and its propagation time, the distance between the defect and the excitation point was measured, and the defect location was predicted as a result. Moreover, the SMEA was applied to locate the railhead defect. The detection mode, the frequency, and the excitation method Were selected through the dispersion curves and modal identification results, and a series of signals of the sampling nodes were obtained using the three-dimensional finite element software ANSYS. The distance between the defect and the excitation point was calculated using the SMEA result. When compared with the structure of the simulated model, the errors obtained were all less than 0.5 m, proving the efficacy of this method in precisely locating rail defects, thus providing an innovated solution for rail defect location.

scholarly journals Acoustic scattering from cylindrical shells bounded by hemispherical endcaps.

1992 ◽  
Vol 91 (4) ◽  
pp. 2470-2470
Author(s):  
Dominique Décultot ◽  
Fernand Léon ◽  
Florence Lecroq ◽  
Gérard Maze
Keyword(s):  
Cylindrical Shells ◽  
Acoustic Scattering

A bioinspired reversible snapping hydrogel assembly

2016 ◽  
Vol 3 (5) ◽  
pp. 422-428 ◽  
Author(s):  
Qian Zhao ◽  
Xuxu Yang ◽  
Chunxin Ma ◽  
Di Chen ◽  
Hao Bai ◽  
...  
Keyword(s):  
Shape Change ◽  
Stable Structure ◽  
Current Work ◽  
Venus Flytrap

Typical hydrogels undergo slow and continuous shape change. Inspired by the Venus Flytrap, the current work presents a hydrogel assembly that can reversibly undergo a non-continuous rapid snapping shape change due to a bi-stable structure of the assembly. In particular, the reversible snapping change goes beyond the Venus Flytrap and is not known in the literature.

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