• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.5
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• pp.363-368
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• 1999

Ultrasonic pulse-echo methods measuring the transit time through specimens have been widely used in determination of ultrasonic velocity and thickness of specimens. Usually, to determine the velocity of the ultrasonic. the transit time of the ultrasonic pulse through specimen is measured by using the ultrasonic measuring equipment such as the oscilloscope including ultrasonic pulser/receiver and the thickness of the specimen is measured by using the length measuring instrument such as micrometer or vernier calipers etc., i. e. each parameter is measured by using each measuring method. In the case of the measuring the thickness of a specimen by using the ultrasonics. the ultrasonic equipments, which measure the thickness, such as the ultrasonic thickness gauge must be calibrated by using the reference block of which the ultrasonic velocity is known beforehand. In the present work, we proposed a new method for simultaneous measurement of ultrasonic velocity and thickness without reference blocks. Experimental results for several specimens show that proposed method have good agreements with those by traditional ultrasonic method.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1826-1828
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• 2004

In this paper, we present an ultrasonic velocity and attenuation measurement system. There are many ultrasonic measurement methods that are used in nondestructive testing applications. They include material property determination, microstructural characterization, and flaw detection. Ultrasonic parameters such as velocity and attenuation are most commonly used in them. Advanced signal analysis which is called "ime-frequency analysis"has been used widely in nondestructive evaluation applications. Wavelet transform is the most advanced technique for processing signals with time-varying spectra. Using the echo waveform gathered by the designed hardware system, we performed simulation of the signal processing algorithms. Then the algorithm is implemented on the system.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.2
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• pp.18-24
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• 1989

Computer-aided high frequency ultrasonic is applied to aluminum oxide(85w%, 94w%, 96w%, and 99w%) MOR(modulus of rupture) samples to evaluate mechanical properties such as density variation, pore content, elastic modulus, shear modulus, and poisson's ratio. Ultrasonic wave velocity and attenuation measurement techniques were used as an evaluator of such properties. Pulse-echo C-Scan images with different fate setting method using 50MHz center frequency 1 inch focal length transducer allows evaluation of density variation and pore content. Elastic modulus calculated with the relation of density and ultrasonic velocity. It shows good reliability as compared with resonance method. Sintered density variation of $0.025g/cm^{3}$, that is 0.6% of theoretical density in $Al_{2}O_{3}$ samples can be observed by ultrasonic velocity measurement. Attenuation measurement method qualitatively agree with 4-point fracture testing result concerning of porosity content.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.122-123
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• 2014

Measurement of the strength of concrete is an important indicator of the safety of the fresh as well as old concrete structures. It is possible to evaluate the strength of the concrete by means of an ultrasonic velocity method which is a kind of non-destructive inspection method for safety diagnostic evaluation of the building structures with aging. Steel embedded in the concrete and age of the concrete may affect ultrasonic pulse velocity. In order to accurately assess the strength of the concrete, it is necessary to understand rebar embedded in the concrete, steel shapes in various forms which effect ultrasonic pulse velocity. In this study, by measuring the velocity of ultrasonic waves generated when the waves pass through the ultrasonic pulse in a direction perpendicular to the reinforcing bars embedded in concrete, the effect of reinforcing bars on ultrasonic velocity accurately was verified and used to estimate the strength of the concrete.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.8
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• pp.559-567
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• 2015

The paper deals with an ultrasonic transducer invented for measuring both flow velocity and pipe thickness. The structure of the transducer is based on the conventional transducers for measuring flow velocity by obliquely transmitting ultrasonic waves to the flow direction. The transducer additionally generates ultrasonic waves transmitting vertically to a pipe for measuring pipe thickness. By measuring flow velocity with the invented transducer and a conventional oblique-incidence transducer and comparing their results, the accuracy of the flow velocity measurement of the invented one was evaluated. By measuring specimen thickness with the invented transducer and a conventional normal-incidence transducer and comparing their results, the accuracy of the thickness measurement of the invented one was evaluated.

• Journal of Biosystems Engineering
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• v.28 no.3
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• pp.239-244
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• 2003

The potential use of ultrasonic technique for firmness measurement of apples was evaluated. Mechanical properties(bioyield deformation, bioyield strength, rupture deformation, ultimate strength, and elastic modulus) and ultrasonic parameters (ultrasonic velocity, attenuation coefficient and the first peak frequency) of the apple flesh during the storage time were measured and analyzed. Ultrasonic parameters were determined from the measurement of ultrasonic wave transmission through the apple flesh specimen. Mechanical properties were obtained by universal testing machine. The bioyield strength, rupture strength, elastic modulus, ultrasonic velocity, and the first peak frequency of the apple flesh decreased with the storage time. The bioyield deformation, rupture deformation, and ultrasonic attenuation coefficient increased with the storage time. The correlation analysis between ultrasonic parameters and mechanical properties and the storage time was performed. The high correlations were found between the storage time and the ultrasonic parameters, and these relationships seem to be useful for determining the firmness of the apple flesh.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.155-161
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• 2012

It was attempted to evaluate the microstructure and quality of various types of cast iron by ultrasonic velocity measurement. Three types of commercial gray cast iron and ductile cast iron were used for this investigation, respectively. One type of the ductile cast iron was heat-treated as a function of annealing time to produce different microstructure. Ultrasonic velocity measurement, microstructural analysis (pearlite area fraction, graphite length and nodularity), and hardness measurement were performed to find empirical correlations among these parameters. Ultrasonic velocity of ductile cast iron was markedly faster than that of gray cast iron. Ultrasonic velocity decreased with the decrease of fraction of pearlite structure. As a quality monitoring parameter of cast iron, potential of ultrasonic velocity was suggested.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.378-386
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• 2002

Multi-path ultrasonic Sow measurement system uncertainty is determined by assigning an expected error of each component of flow measurement and then defining the total flow measurement uncertainty as square root of the sum of squared values of the individual error. Sources of uncertainty for flow measurement are geometry, transit time and velocity profile integration uncertainty. A theoretical uncertainty model for multi-path ultrasonic transit time flowmeter configured with parallel 5 chords, is derived from and calculated by dry calibration method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.2
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• pp.148-156
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• 2016

The paper deals with improvement of a piezoelectric ultrasonic transducer for measuring both pipe thickness and flow velocity. The transducer structure is based on the conventional transducers for measuring flow velocity by obliquely transmitting ultrasonic waves to the flow direction. The transducer invented earlier for measuring flow velocity and pipe thickness had an advantage of including only one piezoelectric disc, but for the thickness measurement the ultrasonic wave had to be reflected twice in a wedge material to be transmitted vertically to a pipe, and thus the wave signal was too weak. The transducer has been improved to transmit waves for thickness measurement vertically to a pipe without any prior reflection by electrically connecting two piezoelectric discs, one for flow velocity and the other for pipe thickness measurement. By comparing the measured results of specimen thickness with the improved transducer and conventional transducers, the accuracies of the improved one have been evaluated in the pipe thickness measurements.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.12
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• pp.38-43
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• 2013

In this paper, the location measurement method for the reliable location data using ultrasonic sensors is proposed for the dimming control of the LED flat lamp. The measurement errors depending on the reflection angle of the object have to be considered to obtain the reliable location data in the ultrasonic sensors. In the experiment, the cause of the measurement errors depending on reflection angle is analyzed and velocity change of ultrasonic wave depending on reflection angle is measured. And the location measurement method depending on velocity change of ultrasonic wave is proposed. From the results, the average absolute deviation of the x-coordinates was 1.47cm when the location measurement method was considered, and it was closer to the true values than the average absolute deviation of the x-coordinates which was 5.89cm without regard to the reflection angle.