• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.4
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• pp.637-643
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• 2002

The objective of this study is to provide a simple methodology to find optimum processing conditions to fabricate sub-micron structured DVD-RAM substrates with superb optical and geometrical properties. It was fecund that the birefringence, which is regarded as one of the most important optical properties for an optical disk, was very sensitive to the mold wall temperature history. Also, the integrity of the replication, represented by the land-groove structure and the radial tilt were influenced by the mold temperature and the compression pressure. A set of optimum conditions were obtained by applying Design of Experiment and the objective functions composed of three different objectives.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.166-171
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• 2004

Since early 1950's fracture mechanics has brought significant impact on structural integrity assessment in a wide range of industries such as power, transportation, civil and petrochemical industries, especially in nuclear power plant industries. For the last two decades, significant efforts have been devoted in developing defect assessment procedures, from which various fitness-for-purpose or fitness-for-service codes have been developed. From another aspect, recent advances in IT (Information Technologies) bring rapid changes in various engineering fields. IT enables people to share information through network and thus provides concurrent working environment without limitations of working places. For this reason, a network system based on internet or intranet bas been appeared in various fields of business. Evaluating the integrity of structures is one of the most critical issues in nuclear industry. In order to evaluate the integrity of structures, a complicated and collaborative procedure is required including regular in-service inspection, fracture mechanics analysis, etc. And thus, experts in different fields have to cooperate to resolve the integrity problem. In this paper, an internet-based cooperative system for integrity evaluation system which adapts IT into a structural integrity evaluation procedure for reactor pressure vessel is introduced. The proposed system uses Virtual Reality (VR) technique, Virtual Network Computing (VNC) and agent programs. This system is able to support 3-dimensional virtual reality environment and to provide experts to cooperate by accessing related data through internet.

• Proceedings of the KWS Conference
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• 1998.10a
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• pp.11-24
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• 1998

The invention of fusion wilding technology has brought on a revolutionary change in manufacturing industry which enables the construction of large scale high temperature plants in chemical, petrochemical and power generation industries. However, among the failure cases of high temperature components, premature failures of weldments have taken a large percentage that indicates the detrimental effect of welding on structural integrity. The accurate prediction of the high temperature behaviour of welded components is thus becoming increasingly important in order to realise an optimised design and maintenance of a plant life. In the present paper, recent research activities on high temperature behaviour of welded structures are briefly summarised. A local deformation measuring technique is proposed to determine the creep properties of weldment constituents. A damage mechanics approach is introduced to study the life reduction and ductility reduction due to the presence of a weld in high temperature structures. Finally, the high temperature creep crack growth in weldments is discussed.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.666-671
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• 2007

To acquire the safety along with durability of mechanical machinery products, we should consider the structural mechanics such as stress, deformation and dynamic vibration characteristics and identify those important aspects in the stage of preliminary design engineering. This cryogenic ball valve is used to transfer the liquified natural gas which temperature is $-196^{\circ}C$, supplied pressure is $168kg/cm^2$. For the cryogenic ball valve, the assurance of structural integrity and operability are essential to meet not only normal, abnormal loading conditions but also functionality during a seismic event. In this thesis, analytical approach and results using finite element analysis and computational method are herein presented to evaluate the aspects of structural integrity along with operability of cryogenic ball valve. In this study, we designed the high pressure cryogenic ball valve that accomplishes zero leakage by elastic seal at normal temperature and metal seal at high temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.7 s.166
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• pp.1104-1111
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• 1999

A brake pedal for the flight control system of the Korean primary trainer is developed using composite material. The development includes the structural design, stress analysis, manufacturing and the qualification tests. A FEM analysis is used for the structural design and stress analysis. Autoclaving process is used to fabricate the composite brake pedal. For the qualification tests, modular fixtures are developed and applied. It is shown that the composite brake pedal developed meets all the structural integrity requirements specified in the military specification for aircraft parts.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.731-740
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• 1995

The objective of this paper is to develop defect assessment technology for integrity evaluation of CANDU pressure tubes. In fracture mechanics analysis, three-dimensional and two-dimensional (line-spring model) finite element analyses were performed to obtain the stress intensity factor for axial and circumferential surface cracks. In leak before break (LBB) analysis, heat transfer analyses for through-wall cracks were performed by considering the cooling effect and the LBB application time was computed. It was shown that the analytical results obtained in this study provide less-conservative but accurate solution for defect assessment of CANDU pressure tubes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1239-1243
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• 2009

To evaluate the structural integrity of the nuclear seismic category penetration cooling water pump under the seismic service conditions the seismic analysis was performed in accordance with IEEE-STD-344 code. The finite element computer program, ANSYS, Version 10.0, is used to perform both a mode frequency analysis and an equivalent static seismic analysis of the pump assembly. The mode frequency analysis results show the fundamental natural frequency is greater than 33 Hz and does not exist in seismic range, thus justifying the use of the static analysis. The stresses resulted from various loadings and their combinations are within the allowable limits specified in the above mentioned IEEE code. The results of the seismic evaluation fully satisfied the structural acceptance criteria of the IEEE code. Accordingly the structural integrity on the pump assembly was proved.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.2
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• pp.48-54
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• 2000

This paper presents the effect of shape of external corrosion in pipeline on failure prediction by using a numerical simulation. The numerical study for the pipeline failure analysis is based on the FEM(Finite Element Method)with an elastic-plstic and large-deformation analysis. Corrosion pits and narrow corrosion grooves in pressurized pipeline were analysed. A failure criterion, based on the local stress state at the corrosion and a plastic collapse failure mechanism, is proposed. The predicted failure stress assessed for the simulated corrosion defects having different corroded shapes along the pipeline axis compared with those by methods specified in ANSI/ASME B31G code and a modified B31G code. It is concluded the corrosion geometry significantly affects the failure behavior of corroded pipeline and categorisation of pipeline corrosion should be considered in the development of new guidance for integrity assessment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.217-225
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• 2003

Grouting internally with grout materials can repair the micro-cracks and micro-voids of construction joints more efficiently than injecting grouts from the surface of cracks. A new internal grouting method using perforated bundled-cables was developed in this study to enhance the structural integrity of the construction joints. The extensive experiments were performed to examine the mechanical behavior of construction joints which are repaired internally by the developed method. The tests were conducted for rectangular-shaped box wall structures and straight wall structures. The strength and permeability tests at grouted construction joints were conducted to evaluate the structural behavior of repaired construction joints. The present study indicates that the internal grouting method developed in this study enhances greatly the performance of construction joints and may be efficiently used for the leak-tight integrity of construction joints in concrete structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.333-338
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• 2007

The concept of "Allowable Load Set (ALS)" introduced by the author allows an easy understanding of load and strength characteristics of a structure in relation to its integrity under uncertainties. Two criteria of safety are introduced: A relative safety index denotes the distance to the boundary of the ALS and a normalized safety index is a distance in terms of functional value. They have been utilized in several examples, including multi-body mechanical systems such as a biomechanical system. Both formulations amount to robust designs in the sense that designs most insensitive to uncertainties are obtained in the context of newly defined safety indices, without using any input probability information.