• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.2
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• pp.40-47
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• 2008

It is known that the adhesive interface testing of the rocket motor using the ultrasonic wave is superior to the other testing methods about the ability to economical detect the defects. But, the signal analysis of the ultrasonic wave takes a lot of time and efforts because the time interval of the transmitted pulse and the received pulse is too short to separate the reflected signals due to the multi-layers of the rocket motor. The ultrasonic testing of rocket motor have only applied to the automatic system about extremely limited areas like the debond in adhesive interface between the motor case and the insulator. In this study the new technique to detect the debond between the liner and the propellant using the property of the resonance and the lamb waves instead of the existing ultrasonic testing was described.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.55-59
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• 2007

It is known that the adhesive interface testing of the rocket motor which using the ultrasonic wave iS superior to the other testing methods about the economically detectable abiliη of the defects. But, the signal analysis of the ultrasonic wave takes too much time and effort that the time interval of the transmitted pulse and the received pulse is too short to be separated the reflected signals because the structure of the rocket motor is multi-layers. The ultrasonic testing of rocket motor have been only applied with automatic system about extremely limited area like the debond in adhesive interface between the motor case and insulator. In this study the new technique to detect the debond between the liner and the propellant using the property of the resonance and Lamb waves was described as comparing the existence ultrasonic testing.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.3
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• pp.302-308
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• 2008

Composite materials are widely used as structural materials for aerospace engineering because of its excellent mechanical properties such as light weight, high stiffness, and low thermal expansion. In driving, impact damage is one of the common but dangerous damages, caused by internal failure of the laminas interface which is not detected by in the surface. Many techniques to detect defects or delaminate between laminates have been reported. Shearography is a kind of laser speckle pattern interferometry with the advantages of non-destructive, non-contact, high resolution and displacement slope measurement. In this paper, the shearography is used to evaluate non-destructively impact damaged surface of the composite material and a measuring method using shearography for the thermal deformation of a impact damaged composite material is discussed. The basic principles of the technique are also described briefly.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.36-43
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• 2016

Carbon fiber-reinforced silicon carbide (Cf-SiC) and SiC / SiC composites have high thermal conductivity, and excellent corrosion and wear resistance, a low coefficient for thermal expansion and are lightweight. This is why they are commonly used in parts of the aerospace industry to develop an aircraft thrust deflector, jet vane, combustion chamber, elevens, body flap, and a shingle. So, understanding how this state-of-the-art Cf-SiC affects both internal and external crack detection and determining issues during the manufacturing process of composite materials, should be evaluated according to valuation techniques in the external environment. In this paper, we apply a non-contact air ultrasonic technique of non-destructive testing techniques to perform a study on internal defect detection identification and assessment of carbon-fiber reinforced silicon carbide composites to perform basic research and applied research.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1940-1945
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• 2007

The wheelsets are one of most important component: damages in wheel tread and press fitted axle are a significant cost for railway industry. Since failure in railway wheelset can cause a disaster, regular inspection of defects in wheels and axles are mandatory. Ultrasonic testing, acoustic emission and eddy current testing method and so on regularly check railway wheelset in service. However, it is difficult to use this method because of its high viscosity and because its sensitivity is affected by temperature. Also, due to noise echoes it is difficult to detect defects initiation clearly with ultrasonic testing. It is necessary to develop a non-destructive technique that is superior to conventional NDT techniques in order to ensure the safety of railway wheelset. In the present paper, the new NDT technique is applied to the detection of surface defects for railway wheelset. To detect the defects for railway wheelset, the sensor for defect detection is optimized and the tests are carried out with respect to surface and internal defects each other. The results show that the surface crack depth of 1.5 mm in press fitted axle and internal crack in wheel could be detected by using the new method. The ICFPD method is useful to detect the defect that initiated in the tread of railway wheelset.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.6
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• pp.426-432
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• 1999

A plus-point eddy current test(ECT) probe was developed to examine the defects on the welds of pumps, valves, and pipings which are the major components of the electric power plants, non-destructive evaluation (NDE) techniques for detecting and sizing the flaws were studied adapting this probe. Differential plus-point ECT probe is consists of two "I"-type coils crossed each other and has an advantage having a small influence on the sensitivity by lift-off variation to the conventional types of probe. The specimens with crack-like electro discharge machining(EDM) notches on the weld of type 304 stainless-steel were fabricated in order to evaluate the plus-point ECT probe response to the flaws. NDE techniques to detect and size the flaws and estimate the flaw type were established with this specimens.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.6
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• pp.479-493
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• 2023

The need for safety management has arisen due to the increasing number of years of operated underground structures, such as tunnels and utility tunnels, and accidents caused by those aging infrastructures. However, in the case of privately managed underground utility ducts, there is a lack of detailed guidelines for facility safety and maintenance, resulting in inadequate safety management. Furthermore, the absence of basic design information and the limited space for safety assessments make applying currently used non-destructive testing methods challenging. Therefore, this study suggests non-destructive inspection methods using ultrasonic and impact-echo techniques to assess the quality of underground structures. Thickness, presence of rebars, depth of rebars, and the presence and depth of internal defects are assessed to provide fundamental data for the safety assessment of box-type general underground structures. To validate the proposed methodology, different conditions of concrete specimens are designed and cured to simulate actual field conditions. Applying ultrasonic and impact signals and collecting data through multi-channel accelerometers determine the thickness of the simulated specimens, the depth of embedded rebar, and the extent of defects. The predicted results are well agreed upon compared with actual measurements. The proposed methodology is expected to contribute to developing safety diagnostic methods applicable to general underground structures in practical field conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.308-313
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• 1995

Non-destructive inspection techniques using laser have been broading their application areas as well as growing their measurement skills together with the rapid development of circumferential technology like fiber optics and computer. The remarkable inspection technique using laser speckle, so-called ESPI is aleady on the stage of on-line testing with commercial products in other nations. Especially, this technique is expected to be applied to the nuclear industry. Because it is proper for the vibration measurement and it can be applied to objects of a high temperature. This paper describes the use of the ESPI system for measuring vibration patterns on the reflecting objects. Using this system, high-quality Jo fringers fso that fringe shift algorthms can be used to determine vibration interferograms recorded by the ESPI system.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.02a
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• pp.17-25
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• 2004

During the past few years, advances have been made in both in X-ray tube and detector technologies. The field of microfocus radioscopy has been established as an important testing process and has expanded into many new industrial applications that require quality control or process optimization. The first nanofocus and multifocus X-ray systems have become available with a focal spot of .5 micron. In the existing range of microfocus X-ray tubes, further improvements have been achieved as well, such as increased long term stability of intensity position constancy. Software, image processing and manipulation techniques have all progressed as well, allowing X-ray to become a formidable non-destructive inspection method for manufacturers in virtually every industry, especially those involved with Electronic Packaging and SMT.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.3
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• pp.185-192
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• 2015

Since real-time monitoring systems, such as early fault detection, have been very important, an infrared thermography technique was proposed as a new diagnosis method. This study focused on damage detection and temperature characteristic analysis of ball bearings using the non-destructive, infrared thermography method. In this paper, for the reliability assessment, infrared experimental data were compared with finite element analysis (FEA) results from ANSYS. In this investigation, the temperature characteristics of ball bearing were analyzed under various loading conditions. Finally, it was confirmed that the infrared thermography technique was useful for the real-time detection of damage to bearings.