• Journal of the korean Society of Automotive Engineers
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• v.15 no.2
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• pp.121-129
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• 1993

Plane strain punch stretching test (PSST) was developed to evaluate stamping formability of sheet materials. In this test, the rectangular specimen of sheet material is uniformly stretched up to fracture by raising a specially designed punch to certainly assure plane strain stretching deformation along the longitudinal direction of the specimen. The stamping formability was evaluated by limit punch height(LPH) in plane strain punch stretching test compared to limit dome height(LDH) in hemispherical punch stretching test. LPH-value in PSST well ranks the stamping formability of various material and correlates with press performance. Moreover by using ultrasonic thickness gauge the plane strain intercept-limit plane strain(FLCo)-in forming limit curve can be accurately determined from thickness measurement around the fracture area. The FLCo derived from thickness measurement well correlates with the results from circle grid analysis for the deformed circle grid marked on the surface of the specimen.

• 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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.545-547
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• 2014

The portable vibration signal-based pipe wall thinning inspection device was developed in this work. Compared to wall-thinning detection using conventional ultrasonic thickness measurement gauge, the proposed device can estimate average wall thickness of wide range and be applied to in-service pipes. The measurement principle of the device was briefly described and the configrations of hardware and software were explained. It was shown that the device can gauge average wall-thickness of test specimens with high precision.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.2
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• pp.170-176
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• 1998

The team mixed PbO, $ZrO_2$, $TiO_2$, $Nb_2O_5$ and $MnCO_3$, to make $Pb[(Zr_{0.54}\;Ti_{0.46})\;Nb_{0.005}]O_3+4%MnCO_3$. The electroded PZT ceramics were poled by 3 kV/mm at $110^{\circ}C$ for 600 s. We assembled the 0.4mm thick PZT slices into ultrasonic transducers. Central frequency of the probe is 5 MHz, which is proper to the thickness gauge for steel pipes and for flaw detector. The probe can detect a disk shape defect of 1mm diameter at 15cm deep in steel block. The new probe's Fresnel zone that the ultrasonic beam do not broaden is 13mm. Over the Fresnel zone, the ultrasonic beam spreads. Half of the beam spread angle of the probe is $4.3^{\circ}-4.6^{\circ}$. This probe can be used for the ultrasonic transducers for non-destructive testing of steel bridges.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.15 no.1
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• pp.46-52
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• 2019

This work proposes a noncontact ultrasonic transducer for detecting wall-thinning of containment liner plates of nuclear power plants by measuring their thickness without physical contact. Because the containment liner plate is designed to prevent atmospheric leakage of radioactive substances under severe nuclear accident, its wall-thinning inspection is important for safety of nuclear power plants. Wall-thinning investigation of containment liner plates have been carried out by measuring their thickness with contact-type ultrasonic thickness gauge by inspectors and needs a lot of time and cost. As an alternative, an electromagnetic acoustic transducer measuring precisely thickness of containment liner plates without any physical contact or couplant was suggested in this research. A transducer generating and measuring shear ultrasonic waves in thickness direction was designed and wave field produced by the transducer was analyzed to verify the design. The working performance of the suggested transducer was tested with carbon steel plate specimens with various thicknesses. The test result shows that the proposed transducer can measure thickness of the specimens precisely without any couplant and implies that swift scanning of wall-thinning of containment liner plates will be possible with the proposed transducer.

• Journal of the Korean Society for Nondestructive Testing
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• v.2 no.2
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• pp.9-16
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• 1983

There are two weak points in a high pressure vessel, one is a corner, the other is a crack on the base. In order to evaluate safety of a department of a corner and a crack like a starfish on the base in a high pressure vessel (working pressure: $130kg/cm^{2}$), which was made by Marison's Process, we analyzed stress by strain gauge, measured thickness and hardness by ultrasonic testing, and were able to test pressure by water pressure from nondestructive testing. Also destructive testings were applied to measure thickness and to observe microstructure and chemical composition of a corner on the base. From the results of the experiment, values of experiment were satisfied with a condition of application. But, it is considered that a crack on the base is to be investigated with more by Fracture Mechanics.

• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.4
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• pp.63-73
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• 2002

This paper presents the results of a ten-day long survey for assessing the possibility of further oil spillage from the sunken tanker, Kyung-Shin(995 G/T), which had sunken in the East Sea, off Pohang City, in February 1988. The survey was conducted using remotely operated vehicle(ROV), manned submersible and ultrasonic thickness gauge in September 2001. The external inspection by the optical camera shows that small scale oil spill has been continued from the sunken ship. It's hull thickness was also measured at several points of the ship, using an ultrasonic sensor for assessing the current corrosion status of the sunken ship. Taking into account the results of this survey and the existing salvage report, it is estimated that the remaining oil in the tanker is approximately 600 ㎘, and this oil could be leaked into marine environment due to continuous severe corrosion if no preventive is taken.

• Journal of the Korean Institute of Gas
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• v.21 no.1
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• pp.18-26
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• 2017

This work proposes an alternative pipe wall-thinning inspection method based on change of eigenfrequencies of shell vibration modes in wall-thinned pipes. It takes much time to detect wall-thinning of pipes using ultrasonic thickness gauge and only a limited number of pipes are under regular inspection. In a pipe with locally decreased thickness, stiffness varies along circumferential direction and natural frequencies of shell vibration modes of the pipe change or frequencies of same modes bifurcate into two different values. Therefore, one can monitor pipe wall-thinning by measuring change of natural frequencies or estimate wall-thinning shape qualitatively. The feasibility of the proposed method was studied by FE vibration analysis for wall-thinned pipes. Modal testing was also carried out for the pipes with artificial wall-thinned section to verify the working performance of the suggested technique.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.2
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• pp.219-226
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• 2020

Nondestructive testing is one of the most commonly used quality inspection methods for evaluating ship structures. However, accurate evaluation is dif icult because various composite materials, such as reinforcements, resin, and fiber-reinforced plastics (FRPs), are used in hulls, and manufacturing quality differences are likely to exist owing to the fabrication environment and the skill level of workers. This possibility is especially true for FRP ships because they are significantly thicker than other structures, such as automobiles and aircraft, and are mainly manufactured using the hand lay-up method. Because the density of a material is a critical condition for ultrasonic inspection, in this study, a hull plate was selected from a vessel manufactured using e-glass fiber, which is widely used in the manufacture of FRP vessels with the weight fraction of the glass content generally considered. The most suitable ultrasonic testing conditions for the glass FRP hull plate were investigated using a pulse-echo ultrasonic gauge. A-scans were performed with three probes (1.00, 2.25, and 5.00 MHz), and the results were compared with those of the hull plate thickness measured using a Vernier caliper. It was found that when the probe frequency was higher, the eco-pulse velocity of the receiver had to be lowered to obtain accurate measurement results, whereas fewer errors occurred at a relatively low probe frequency.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.96-104
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• 2009

An anatomically detailed elderly human body model is under development. Using the anthropometric database of domestic nation-wide size survey, SizeKorea, a standard size and shape of 50th %tile elderly was constructed. Through the local recruitment process, a male volunteer with 71 years of age, 163cm of height and 63kg of weight has been selected. The exterior (skin) and interior (skeleton and organ) geometries were acquired from whole body 3D laser scan and various medical images such as CT, X-ray, and Ultrasonic of the volunteer. A particular attention has been paid into the combining process of exterior and interior geometries especially for joint articulation positions since they were measured at different postures (sitting vs. supine). A whole ribcage of PMHS which possessed similar anthropometry and age of standard 50th %tile elderly was prepared and dissected for the precise gauge of cortical rib bone thickness distributions. After completing the morphological construction of elderly human body, the finite element modeling will be processed by meshing elements and assigning mechanical properties to various biological tissues which reflect the aging effect.