• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.3
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• pp.245-253
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• 2008

A precise description of the material is a key point to obtain reliable results when using wave propagation codes. In the case of multipass welds, the material is very difficult to describe due to its anisotropic and heterogeneous properties. Two main advances are presented in the following. The first advance is a model which describes the anisotropy resulting from the metal solidification and thus the model reproduces an anisotropy that is correlated with the grain orientation. The model is called MINA for modelling anisotropy from Notebook of Arc welding. With this kind of material model1ing a good description of the behaviour of the wave propagation is obtained, such as beam deviation or even beam division. But another advance is also necessary to have a good amplitude prediction: a good quantification of the attenuation, particularly due to grain scattering, is also required as far as attenuation exhibits a strong anisotropic behaviour too. Measurement of attenuation is difficult to achieve in anisotropic materials. An experimental approach has been based both on the decomposition of experimental beams into plane waves angular spectra and on the propagation modelling through the anisotropic material via transmission coefficients computed in generally triclinic case. Various examples of results are showed and also some prospects to continue refining numerical simulation of wave propagation.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.1
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• pp.25-32
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• 2015

Many crack flaws have been detected at tubing seal weld zone in Steam Generator with Alloy600 material tubes. it is very difficult to discriminate the signal from parent material and that from weld zone because weld zone gives complicated ECT signal due to manufacturing processes. ECT signal analysis in the seal weld zone is very important since the tubes with crack in this area shall be out of service by plugging. The purpose of this paper is to distinguish between Parent material and Weld Zone ECT signal in the seal weld zone through the demonstration test of Steam Generator seal weld mock-up.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.801-809
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• 2000

Until recently as a method of repairing leaking problem, generally urethane series were used for many structures as subway, box culvert etc. However the lacking of sufficient penetration capacity have made it difficult to repair such structures completely. Now, we could achieve enhanced quality of repairing work by using new material which was compounded of urethane series and cement series properly. This material can penetrate concrete structure efficiently and move interactively with the structure in case of the thermal expansion. Besides of this, we could prevent expecting leakage through several improvements on the aspects of design, materials and site implementation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.44-48
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• 1993

Recently, superconducting cable has attracted a great deal of interest from the viewpoint of energy saving, one of the most important and difficult problems to be solved to assure the high reliability, safety and economy of cable is breakdown is cryogenic temperature. In this paper, we will report on the characteristics and mechanisms of the breakdown and creeping discharge in cryogenic liquids, dual role of those as the cooling and insulating material, and composited system of cryogenic liquid - gas taking into consideration for application.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.254-258
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• 2003

Electronic Speckle Pattern for quantitative evaluation of a impact defect inside of composite material plate are described. The impact on composite material makes inside delamination which is difficult to detect visual inspection and ultrasonic testing due to non-homeogenous structure. This paper proposes the quantitative evaluation technique of defects under real impact. Artificial defects are designed inside of composite plate for development of inspection technique and real defects under impact are inspected and compared with results of visual inspection.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2059-2063
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• 2004

Most power plants have operated many independent computerize systems for maintenance. Independence of systems have caused complexity of business process and inconvenience of computer system management. Because the equipment and material master data is not standardize and structurize, it is difficult to manage equipment maintenance history and material delivery. Especially equipment classification criterion is important for standardization of every maintenance information. It is necessary to integrate function of independent systems for business process simplification and rapid work flow. this paper provides equipment classification criterion design and system integration method with the case of live system development.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.64-65
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• 2020

Oyster shells are difficult to grind, while oyster shell powders have coarse and coarse grains, whereas egg shell powder, the same high calcium material, has small and soft particles and has opposing properties. In order to study the change in flexural and compressive strength by designing different mixing ratios using 50% of oyster shell powder and egg shell powder as a filling material. As a result of the experiment, there is almost no difference in the result.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.7-12
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• 2009

The machining process of ceramics can be characterized by cracking and brittle fracture. In the machining of ceramics, edge chipping and crack propagation are the principal reasons to cause surface integrity deterioration. Such phenomenon can cause not only poor dimensional and geometric accuracy, but also possible failure of the ceramic parts. Thus, traditional ceramics are very difficult-to-cut materials. Generally, ceramics are machined using conventional method such as grinding and polishing. However these processes are generally costly and have low MRR(material removal rate). To overcome such problems, in this paper, h-BN powder, which gives good cutting property, is added for the fabrication of machinable ceramics by volume of 10 and 15%. The purpose of this study is an analysis of endmill's rake angle for appropriate tools design and manufacturing for the machinable ceramics. In this study, Experimental works are executed to measure cutting force, surface roughness, tool fracture, on different axial rake angle of endmills. Cutting parameters, namely, feed, cutting speed and depth of cut are used to accomplish purpose of this paper. Required experiments are performed, and the results are investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.728-733
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• 2008

Though multi-panel structures lined with a poroelastic material have been widely used to reduce sound transmission in various fields, most of the previous works to design them were conducted by repeated analyses or experiments based on initially given configurations or sequences. Therefore, it was difficult to obtain the optimal sequence of multi-panel structures lined with a poroelastic material yielding superior sound isolation capability. In this work, we propose a new design method to sequence a multi-panel structure lined with a poroelastic material having maximized sound transmission loss. Being formulated as a one-dimensional topology optimization problem for a given target frequency, the optimal sequencing of panel-poroelastic layers is systematically carried out in an iterative manner. In this method, a panel layer is expressed as a limiting case of a poroelastic layer to facilitate the optimization process. This means that main material properties of a poroelastic material are treated as Interpolated functions of design variables. The designed sequences of panel-poroelastic layers were shown to be significantly affected by the target frequencies; more panel layers were used at higher target frequencies. The sound transmission loss of the system was calculated by the transfer matrix derived from Biot's theory.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.74-74
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• 2009

The ArF PR mask was. developed to overcome the limit. of sub 40nm patterning technology with KrF PR. But ArF PR difficult to meet the required PR selectivity by thin PR thickness. So need to the multi-stack mask such as amorphous carbon layer (ACL). Generally capacitively coupled plasma (CCP) etcher difficult to make the high density plasma and inductively coupled plasma (ICP) type etcher is more suitable for multi stack mask etching. Hybrid Coupled Plasma source (HCPs) etcher using the 13.56MHz RF power for ICP source and 2MHz and 27.12MHz for bias power was adopted to improve the process capability and controllability of ion density and energy independently. In the study, the oxide trench which has the multi stack layer process was investigated with the HCPs etcher (iGeminus-600 model DMS Corporation). The results were analyzed by scanning electron microscope (SEM) and it was found that etching characteristic of oxide trench profile depend on the multi-stack mask.