ABOUT SOME FEATURES OF APPLICATION OF A TANDEM TECHNIQUE IN THE ULTRASONIC TESTING

2020 ◽  
pp. 4-16
Author(s):  
V. N. Danilov
Keyword(s):  
Shear Wave ◽  
Ultrasonic Testing ◽  
Small Distance ◽  
Bottom Surface ◽  
Ultrasonic Control ◽  
Base Distance ◽  
Significant Distance

On the basis of received before the formula of an acoustic сhannel for the circuit of the ultrasonic control the tandem technique and a reflector as a side drilled hole carries out calculations echo signals for various base distances, depths of reflector and angles of probes. Influence on amplitude of a registered signal of a choice of position of a point of reflection on depth of the control is shown. It is established, that mutual replacement of positions of transmitting and receiving probes with identical parameters in a tandem technique practically has not an effect for amplitude of a registered signal. Influence on amplitude of a signal of distinction of angles of transmitting and receiving probes is shown. Comparison of the signals received at use of the circuit of the control on a tandem technique with reflection of a shear wave from a bottom surface and at use of the circuit of a path for separate angle probes with reflection of a wave only from a surface of defect has shown, that a choice of base distance between probess for the point of reflection which are taking place on small distance from a bottom surface, provides also an opportunity of detection of volumetric defects on significant distance from this surface.

Features of ultrasonic control of butt welded joints of polyethylene pipes

2020 ◽  
pp. 46-52
Author(s):  
N.P. Aleshin ◽  
D.M. Kozlov ◽  
L.YU. Mogilner
Keyword(s):  
Quality Control ◽  
Welded Joints ◽  
Ultrasonic Testing ◽  
Ultrasonic Inspection ◽  
Mechanical Tests ◽  
Ultrasonic Control ◽  
Lack Of Fusion ◽  
Polyethylene Pipes ◽  
End To End

The reliability of ultrasonic testing (UT) of the quality of welded joints of polyethylene pipelines, made end-to-end with a heated tool, is considered in comparison with mechanical tests and radiography. The greatest detection of solid defects is provided by ultrasonic inspection with the use of chord tipe probes (not less than 90 %). When detecting defects translucent for ultrasound (lack of penetration, lack of fusion, etc.), the reliability decreases to 70÷80 %. Keywords: welding, polyethylene pipeline, quality control, ultrasonic testing, chord tipe probe. [email protected]

Measurement of wave velocities and attenuation using an ultrasonic test system

2004 ◽  
Vol 41 (5) ◽  
pp. 844-860 ◽  
Author(s):  
Eng-Choon Leong ◽  
Sir-Hoon Yeo ◽  
Harianto Rahardjo
Keyword(s):  
Shear Wave ◽  
Elastic Constants ◽  
Ultrasonic Testing ◽  
Small Strain ◽  
Test System ◽  
Ultrasonic Test ◽  
Reliable Estimate ◽  
Frequency Spectra ◽  
Acoustic Coupling ◽  
Wave Velocities

The use of ultrasonic testing to determine pulse velocities and small-strain elastic constants for rocks has been standardized in American Society for Testing and Materials (ASTM) standard D2845-95. However, the use of ultrasonic testing to determine pulse velocities and small-strain elastic constants of soils is less common, as soils have higher damping characteristics which result in measurement difficulty. The signal transmitted through soil is weak and very noisy. As a result, the signal must be properly processed to provide a reliable estimate of the wave travel time. In this paper, an ultrasonic test system consisting of compression and shear wave transducers, a pulser, and a data-acquisition system is evaluated for measurement of both compression and shear wave velocities. Among the specimens tested were fully saturated and unsaturated soil specimens. The effects of acoustic coupling and signal processing on the transmitted pulse were investigated. The strain levels associated with the determination of the wave velocities were also measured. Furthermore, a method for determining attenuation characteristics for soil specimens from the frequency spectra is suggested.Key words: laboratory, compression wave, shear wave, velocity, attenuation, ultrasonic.

IDENTIFICATION AND RELIABILITY OF CONTROL IN ULTRASONIC FLAW DETECTION AND DEFECTOMETRY

2020 ◽  
pp. 4-17
Author(s):  
V. G. Badalyan
Keyword(s):  
Ultrasonic Testing ◽  
Flaw Detection ◽  
Roc Curves ◽  
Probability Of Detection ◽  
Ultrasonic Control ◽  
Ultrasonic Flaw Detection ◽  
Control Techniques ◽  
Additional Information ◽  
Ultrasonic Flaw ◽  
Non Destructive

The effectiveness of methods and means of ultrasonic non-destructive control (ultrasonic control) is evaluated by the probability of detecting defects and the reliability of the results of the control. In this work, we reserch the behavior of PoD(a) – the defect detection function, which describes the dependence of the probability of detection of defects on their height, and estimates the reliability of control by means of ROC analysis of the control data. An analysis of the PoD curves obtained by ultrasonic testing with ultrasonic flaw detection and ultrasonic flaw detection instruments demonstrates significantly greater reliability of the use of defectometry techniques and devices. ROC curves constructed using ultrasonic defectometry data make it possible to evaluate the reliability of control of defects of various heights. Analysis of ROC curves provides additional information for optimizing ultrasonic control techniques. The studies were carried out on the data array of ultrasonic testing of welded joints with real cracks.

A New Defect in Polyethylene Single Crystals

1973 ◽  
Vol 31 ◽  
pp. 70-71
Author(s):  
E. L. Thomas ◽  
S. L. Sass
Keyword(s):  
Single Crystals ◽  
Screw Dislocation ◽  
Small Distance ◽  
Dipole Model ◽  
Dislocation Dipole ◽  
Chain Folding ◽  
Black And White ◽  
Polymer Crystal ◽  
Different Types

In polyethylene single crystals pairs of black and white lines spaced 700-3,000Å apart, parallel to the [100] and [010] directions, have been identified as microsector boundaries. A microsector is formed when the plane of chain folding changes over a small distance within a polymer crystal. In order for the different types of folds to accommodate at the boundary between the 2 fold domains, a staggering along the chain direction and a rotation of the chains in the plane of the boundary occurs. The black-white contrast from a microsector boundary can be explained in terms of these chain rotations. We demonstrate that microsectors can terminate within the crystal and interpret the observed terminal strain contrast in terms of a screw dislocation dipole model.

Unbiased estimation of particle number and sizes using the new stereological tools: the disector, the fractionator, the selector, and the nucleator — or just point-sampled intercepts

1988 ◽  
Vol 46 ◽  
pp. 428-429
Author(s):  
H.J.G. Gundersen
Keyword(s):  
Particle Number ◽  
Small Distance ◽  
Parallel Plane ◽  
Unbiased Estimation ◽  
Severe Problem ◽  
New Era ◽  
Size And Shape ◽  
Distinct Property ◽  
Sectioned Tissue

Previously, all stereological estimation of particle number and sizes were based on models and notoriously gave biased results, were very inefficient to use and difficult to justify. For all references to old methods and a direct comparison with unbiased methods see recent reviews.The publication in 1984 of the DISECTOR, the first unbiased stereological probe for sampling and counting 3—D objects irrespective of their size and shape, signalled the new era in stereology — and give rise to a number of remarkably simple and efficient techniques based on its distinct property: It is the only known way to obtain an unbiased sample of 3-D objects (cells, organelles, etc). The principle is simple: within a 2-D unbiased frame count or sample only cells which are not hit by a parallel plane at a known, small distance h.The area of the frame and h must be known, which might sometimes in itself be a problem, albeit usually a small one. A more severe problem may arise because these constants are known at the scale of the fixed, embedded and sectioned tissue which is often shrunken considerably.

Liver Elastography in Healthy Children Using Three Different Systems – How Many Measurements Are Necessary?

2020 ◽  
Author(s):  
Anders Batman Mjelle ◽  
Anesa Mulabecirovic ◽  
Roald Flesland Havre ◽  
Edda Jonina Olafsdottir ◽  
Odd Helge Gilja ◽  
...  
Keyword(s):  
Shear Wave ◽  
Transient Elastography ◽  
Intraclass Correlation ◽  
Age Groups ◽  
Liver Stiffness ◽  
Shear Wave Elastography ◽  
Healthy Children ◽  
Significant Difference ◽  
Pediatric Liver Disease ◽  
Liver Elastography

Abstract Purpose Liver elastography is increasingly being applied in screening for and follow-up of pediatric liver disease, and has been shown to correlate well with fibrosis staging through liver biopsy. Because time is of the essence when examining children, we wanted to evaluate if a reliable result can be achieved with fewer acquisitions. Materials and Methods 243 healthy children aged 4–17 years were examined after three hours of fasting. Participants were divided into four age groups: 4–7 years; 8–11 years; 12–14 years and 15–17 years. Both two-dimensional shear wave elastography (2D-SWE; GE Logiq E9) and point shear wave elastography (pSWE; Samsung RS80A with Prestige) were performed in all participants, while transient elastography (TE, Fibroscan) was performed in a subset of 87 children aged 8–17 years. Median liver stiffness measurement (LSM) values of 3, 4, 5, 6, 7, and 8 acquisitions were compared with the median value of 10 acquisitions (reference standard). Comparison was performed for all participants together as well as within every specific age group. We investigated both the intraclass correlation coefficient (ICC) with absolute agreement and all outliers more than 10 %, 20 % or ≥ 0.5 or 1.0 kPa from the median of 10 acquisitions. Results For all three systems there was no significant difference between three and ten acquisitions, with ICCs ≥ 0.97. All systems needed 4 acquisitions to achieve no LSM deviating ≥ 1.0 kPa of a median of ten. To achieve no LSM deviating ≥ 20 % of a median of ten acquisitions, pSWE and TE needed 4 acquisitions, while 2D-SWE required 6 acquisitions. Conclusion Our results contradict recommendations of 10 acquisitions for pSWE and TE and only 3 for 2D-SWE.

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