scholarly journals Internal Cylinder Identification Based on Different Transmission of Longitudinal and Shear Ultrasonic Waves

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 723
Author(s):  
Wen-Bei Liu ◽  
Wen-Bo Yan ◽  
Huan Liu ◽  
Cheng-Guo Tong ◽  
Ya-Xian Fan ◽  
...  
Keyword(s):  
High Frequency ◽  
Visual Inspection ◽  
Shear Waves ◽  
Ultrasonic Waves ◽  
Transmission Characteristics ◽  
Internal Defects ◽  
Longitudinal And Shear Waves ◽  
Defect Area ◽  
Ultrasonic Techniques ◽  
The Difference

We have built a Fizeau fiber interferometer to investigate the internal cylindrical defects in an aluminum plate based on laser ultrasonic techniques. The ultrasound is excited in the plate by a Q-switched Nd:YAG laser. When the ultrasonic waves interact with the internal defects, the transmitted amplitudes of longitudinal and shear waves are different. The experimental results show that the difference in transmission amplitudes can be attributed to the high frequency damping of internal cylinders. When the scanning point is close to the internal defect, the longitudinal waves attenuate significantly in the whole defect area, and their amplitude is always smaller than that of shear waves. By comparing the transmitted amplitudes of longitudinal and shear waves at different scanning points, we can achieve a C scan image of the sample to realize the visual inspection of internal defects. Our system exhibits outstanding performance in detecting internal cylinders, which could be used not only in evaluating structure cracks but also in exploring ultrasonic transmission characteristics.

Estimation of Local Elastic Moduli of Carbon-Containing Materials by Laser Ultrasound

2018 ◽  
Vol 769 ◽  
pp. 96-101 ◽  
Author(s):  
Ivan A. Shibaev ◽  
Dmitry V. Morozov ◽  
Oleg L. Dudchenko ◽  
Ilya A. Pavlov
Keyword(s):  
Chemical Composition ◽  
Shear Modulus ◽  
Elastic Properties ◽  
Precision Measurement ◽  
Elastic Moduli ◽  
Pyrolytic Graphite ◽  
Shear Waves ◽  
Laser Ultrasound ◽  
Longitudinal And Shear Waves ◽  
Ultrasonic Techniques

The elastic properties of two carbon-containing materials are investigated. Shungite rock is a natural nanocomposite; isotropic pyrolytic graphite is an artificial material. Precision measurement of the local velocities of longitudinal and shear waves propagating in shungite and isotropic pyrographite samples was performed by laser ultrasonic techniques. Young's modulus, the shear modulus and Poisson's ratio are calculated, and the chemical composition of the samples is given.

Numerical Investigation of Propagation of Ultrasonic Waves in the Waveguides with Mode Conversion

2013 ◽  
Vol 543 ◽  
pp. 219-222
Author(s):  
Elena Jasiūnienė ◽  
Egidijus Žukauskas ◽  
Rymantas Kažys
Keyword(s):  
Numerical Investigation ◽  
Longitudinal Wave ◽  
Mode Conversion ◽  
Incidence Angle ◽  
Ultrasonic Transducer ◽  
Shear Waves ◽  
Ultrasonic Waves ◽  
Ultrasonic Transducers ◽  
Special Cases ◽  
Longitudinal And Shear Waves

Ultrasonic investigation techniques are widely used in materials characterisation and non-destructive testing applications. In special cases of applications, such as investigation of properties of melted polymers, metals and hot liquids, measurements must be performed in a wide temperature range. However conventional piezoelectric transducers cannot withstand higher temperatures than the Curie temperature. Therefore in order to protect conventional ultrasonic transducers from influence of a high temperature and to avoid depolarization, measurements must be performed using special waveguides with a low thermal conductivity between the object under investigation and the ultrasonic transducer. For measurements of the material properties, such as viscoelastic properties of materials, additional shear wave transducers must be used. In this work approach how to excite both, longitudinal and shear waves using special waveguides with mode conversion, using pair of conventional ultrasonic longitudinal wave transducers is presented. In this work numerical investigation of propagation of longitudinal and shear ultrasonic waves in the waveguides with mode conversion using finite element method and CIVA software was carried out. Modelling of propagation of simultaneously generated longitudinal and shear waves using pair of longitudinal ultrasonic transducers was performed. Influence of temperature gradient to the required incidence angle of the longitudinal wave was evaluated.

High Frequency Viscoelasticity of Carbon Black Filled Compounds

1996 ◽  
Vol 69 (5) ◽  
pp. 786-800 ◽  
Author(s):  
M. Gerspacher ◽  
C. P. O'Farrell ◽  
L. Nikiel ◽  
H. H. Yang ◽  
F. Le Méhauté
Keyword(s):  
Carbon Black ◽  
High Frequency ◽  
Dynamic Properties ◽  
Shear Waves ◽  
Crosslinking Density ◽  
Filler Loading ◽  
Wave Measurements ◽  
Rubber Compounds ◽  
Longitudinal And Shear Waves ◽  
Laboratory Tool

Abstract A high frequency viscoelasticity spectrometer, using the state-of-the-art ultrasonic technology, was constructed. The longitudinal and shear waves characteristics were measured in rubber compounds to obtain the attenuation coefficient, α, and sound velocity, v Preliminary results were obtained for a number of filled and unfilled polymers. The grade of carbon black used, filler loading, crosslinking density and filler dispersion were varied during the study. Temperature sweepS from −100°C to +60°C were also studied. It was found that the polymer type had a greater influence on α and v than did the grade of carbon black, loading or dispersion. The experimental data show that shear waves do not propagate in the rubbery state. Above the glass transition temperature, Tg, the longitudinal wave measurements could be sufficient to determine the high frequency dynamic properties of filled and unfilled polymers to characterize a tire tread compound. The temperature sweep measurements allowed the determination of the Tg of polymers at high frequency. It is proposed that the described method of measuring α and v be used as a laboratory tool for potential tire traction prediction.

Comparison of In-the-Ear and Over-the-Ear Hearing Aid Fittings

1986 ◽  
Vol 51 (4) ◽  
pp. 362-369 ◽  
Author(s):  
Donna M. Risberg ◽  
Robyn M. Cox
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Comparative Evaluation ◽  
Speech Intelligibility ◽  
Hearing Aid ◽  
Hearing Aid Fitting ◽  
The Difference ◽  
Functional Gain ◽  
The Relationship

A custom in-the-ear (ITE) hearing aid fitting was compared to two over-the-ear (OTE) hearing aid fittings for each of 9 subjects with mild to moderately severe hearing losses. Speech intelligibility via the three instruments was compared using the Speech Intelligibility Rating (SIR) test. The relationship between functional gain and coupler gain was compared for the ITE and the higher rated OTE instruments. The difference in input received at the microphone locations of the two types of hearing aids was measured for 10 different subjects and compared to the functional gain data. It was concluded that (a) for persons with mild to moderately severe hearing losses, appropriately adjusted custom ITE fittings typically yield speech intelligibility that is equal to the better OTE fitting identified in a comparative evaluation; and (b) gain prescriptions for ITE hearing aids should be adjusted to account for the high-frequency emphasis associated with in-the-concha microphone placement.

scholarly journals Hyperfine structure in the arc spectrum of cæsium and nuclear rotation

1928 ◽  
Vol 121 (787) ◽  
pp. 432-447 ◽  
Keyword(s):  
Hyperfine Structure ◽  
Nuclear Spin ◽  
High Frequency ◽  
Principal Series ◽  
Very High Frequency ◽  
Nuclear Rotation ◽  
Higher Temperature ◽  
The Difference ◽  
Mechanical Moment ◽  
Very High

The arc spectrum of cæsium was investigated with the object of finding whether any of its lines possessed hyperfine structure, resulting from a nuclear magnetic moment, due to a quantised nuclear spin. The lines belonging to the principal series should, owing to the greater degree of penetration of the electron in the (1 s or 6 1 ) orbit, and the correspondingly greater interaction, show the greatest effect. The lines of the principal series are very easily broadened if the vapour pressure of the metal becomes high, so that great care had to be used in obtaining the spectrum of cæsium at a sufficiently low temperature. The most satisfactory method of excitation was found to be the application by means of external electrodes of a very high frequency alternating current to a tube filled with helium at about 2 mm. pressure containing a small quantity of cæsium. The tube required slight heating to bring out the cæsium lines; without this the helium spectrum was very much stronger than the metallic spectrum. At a very low vapour pressures of cæsium the discharge was blue in colour. Under these conditions the lines of the principal series showed no broadening greater than that due to thermal agitation, but at a slightly higher temperature the colour of the discharge became purple and the lines broadened. The lines belonging to the principal series were found to be very close doublets with very nearly constant frequencies differences. A theory is worked out which explains the origin of these doublets, assuming a nuclear spin of one half quantum; by correlating the difference in the separation of the hyperfine structure doublets in the 1 s — m 2 p 3/2 lines and the 1 s — m 2 p 1/2 lines, it is shown that a ratio of the magnetic to the mechanical moment of the nucleus about twice as great as the corresponding ratio for the electron would account for the observed frequency differences. The spectral notation used throughout is that of Hund. The results are compared with those found for the hyperfine structure of some of the bismuth lines by Back and Goudsmid, and are found to be in satisfactory agreement. A selection principle is found which applies both to the bismuth and the cæsium spectrum.

Accuracy and precision in stock separation of north-east Arctic and Norwegian coastal cod by otoliths - comparing readings, image analyses and a genetic method

2005 ◽  
Vol 56 (5) ◽  
pp. 753 ◽  
Author(s):  
Erik Berg ◽  
Tuula H. Sarvas ◽  
Alf Harbitz ◽  
Svein Erik Fevolden ◽  
Arnt Børre Salberg
Keyword(s):  
Visual Inspection ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Complete Separation ◽  
Arctic Cod ◽  
Genetic Method ◽  
North East ◽  
Accuracy And Precision ◽  
Growth Zones ◽  
The Difference

The distinction between north-east Arctic cod and Norwegian coastal cod, two major groups of Atlantic cod (Gadus morhua L.), has for many years been based on different distance and shape similarities between the two first translucent growth zones in the otoliths, subjectively decided by visual inspection in a binocular. To analyse the certainty of this technique, four independent readers have classified 263 cod otoliths in total from five different geographical areas. For three of the readers, between 82% and 89% of the classification results coincided with independent results based on genetic analyses. Further, 38 cod otoliths, where the readers were certain of the classification (21 north-east Arctic cod and 17 coastal cod) were classified by several image analysis methods. A complete separation was obtained by using the ratio of the circumferences of the two zones, providing a typical ratio of approximately 2 for coastal and 1.5 for north-east Arctic cod. The otolith method for separating the two types of cod has been considered adequately accurate in assessing the two stocks of cod. However, the method is sensitive to subjective interpretation, and action needs to be taken to minimise the difference in interpretation among otolith readers.

A Study of the Effect of Extended Hounsfield Unit Range and Voxel Size on Defect Detection in Friction Stir Welds

2020 ◽  
Author(s):  
Ahmad M. R. Baydoun ◽  
Ramsey F. Hamade
Keyword(s):  
Gamma Rays ◽  
Dissimilar Materials ◽  
Hounsfield Unit ◽  
Ct Scanning ◽  
Ultrasonic Waves ◽  
X Rays ◽  
Internal Defects ◽  
Voxel Size ◽  
X Ray ◽  
Friction Stir

Abstract Friction stir welding (FSW) is a novel welding method that is garnering attention, in part, due to its ability to join dissimilar materials. One of the challenges in producing dissimilar friction welded joints is ensuring the welds are defect-free. Nondestructive testing (NDT) methods such as ultrasonic waves, gamma rays, X-rays, and X-ray CT, are gaining popularity as a method to detect internal defects in FSW joints. In this study, dissimilar AA1050-AA6061-T6 FSW lap welds are Manufactured and then examined using an NDT X-ray CT technique. The effects of two critical X-ray CT scanning parameters (voxel size and Hounsfield unit (HU)) on the detection of internal defects are investigated. The samples are scanned via X-ray CT at two different voxel sizes (2.457 E−02 and 1.420 E−03 mm3) and two HU ranges (12-bit and 16-bit depth). The generated Digital Imaging and Communications in Medicine (DICOM) images are segmented based on a proper HU threshold found via the Otsu thresholding method. The findings show that Small voxel size (higher resolution) improves the ability of detecting internal defects and improves the effectiveness of the thresholding process. Higher HU range results in a wider separation between detected material peaks, thus enhancing the effectiveness of the thresholding process as well.

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