The present study is aimed at expanding flexibility and application area of nonlinear acoustic modulation (NAM-) technique by combining the benefits of noncontact ultrasound excitation (remote locating and imaging of defects) with sensitivity of nonlinear methods in a new air-coupled NAM-version. A pair of focused air-coupled transducers was used to generate and receive (high-frequency) longitudinal or flexural waves in plate-like samples. Low-frequency (LF-) vibrations were excited with a shaker or a loudspeaker. Temporal and spectral analysis of the output signal revealed an extremely efficient nonlinear amplitude modulation and multiple frequency side-bands for sound transmission and flexural wave propagation through cracked defects. On the contrary, a negligible modulation was observed for large and medium scale inclusions and material inhomogeneities (linear defects). A new subharmonic mode of the NAM was observed at high excitation levels. It was also shown for the first time that nonlinear vibrations of cracks resulted in radiation of a very high-order harmonics (well above 100) of the driving excitation in air that enabled imaging of cracks remotely by registration their highly nonlinear "acoustic emission" with air-coupled transducers.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1016/j.ultras.2003.12.022 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
High sound pressure piezoelectric micromachined ultrasonic transducers using sputtered potassium sodium niobate.
Microsyst Nanoeng
December 2024
Department of Mechanical Engineering, University of California, Berkeley, CA, 94720, USA.
This work presents air-coupled piezoelectric micromachined ultrasonic transducers (pMUTs) with high sound pressure level (SPL) under low-driving voltages by utilizing sputtered potassium sodium niobate KNaNbO (KNN) films. A prototype single KNN pMUT has been tested to show a resonant frequency at 106.3 kHz under 4 V with outstanding characteristics: (1) a large vibration amplitude of 3.
View Article and Find Full Text PDFA Composite Pulse Excitation Technique for Air-Coupled Ultrasonic Detection of Defects in Wood.
Sensors (Basel)
November 2024
College of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037, China.
To overcome the problems of the low signal-to-noise ratio and poor performance of wood ultrasonic images caused by ring-down vibrations during the ultrasonic quality detection of wood, a composite pulse excitation technique using a wood air-coupled ultrasonic detection system is proposed. Through a mathematical analysis of the output of the ultrasonic transducer, the conditions necessary for implementing composite pulse excitation were analyzed and established, and its feasibility was verified through COMSOL simulations. Firstly, wood samples with knot and pit defects were used as experimental samples.
View Article and Find Full Text PDFContactless ultrasound spectroscopy for testing state-of-charge and integrity in lithium-ion batteries.
iScience
October 2024
Ultrasonic and Sensors Technologies Department (ITEFI), Spanish National Research Council (CSIC), 28006 Madrid, Spain.
Lithium-ion batteries (LIBs) are playing nowadays a key role in the decarbonization of the economy. However, safety issues and the lack of an accurate performance predictor after manufacturing led to the application of non-destructive methods in this field that can assess their condition. Contact ultrasounds have been successfully applied in recent years in this regard, mainly in research facilities, proving the potential of ultrasonic waves to collect meaningful information.
View Article and Find Full Text PDFRevealing regional variations in scleral shear modulus in a rabbit eye model using multi-directional ultrasound optical coherence elastography.
Sci Rep
September 2024
Instituto de Óptica, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
The mechanical properties of the sclera play a critical role in supporting the ocular structure and maintaining its shape. However, non-invasive measurements to quantify scleral biomechanics remain challenging. Recently introduced multi-directional optical coherence elastography (OCE) combined with an air-coupled ultrasound transducer for excitation of elastic surface waves was used to estimate phase speed and shear modulus in ex vivo rabbit globes (n = 7).
View Article and Find Full Text PDFStudy on the radiation directivity of a ring-excited thin circular plate with a fixed boundary.
Ultrasonics
December 2024
Shaanxi Key Laboratory of Ultrasonics, School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, China.
Air-coupled transducer with a flat plate structure have many applications in the fields of ground weather observation, ultrasonic defoaming, and directional strong acoustic radiation. In this paper, an analytical equation of the far-field radiation directivity of a fixed boundary ring-excited thin circular plate (RTCP) is deduced using Rayleigh integration method. A finite element model of the RTCP is established, and the relationship between the far-field radiation directivity and the excitation position, excitation area and working frequency is studied by considering the third-order axisymmetric flexural vibration of the RTCP.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!