• Journal of Welding and Joining
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• v.25 no.1
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• pp.63-69
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• 2007

Once assessment of material failure characteristics is captured precisely in a unified way, it can bedirectly incorporated into the structural failure assessment under various loading environments, based on the theoretical backgrounds so called Local Approach to Fracture. The aim of this study is to develop a numerical fatigue test method by continuum damage mechanics applicable for the assessment of structural integrity throughout crack initiation and structural failure based on the Local Approach to Fracture. The generalized elasto-visco-plastic constitutive equation, which can consider the internal damage evolution behavior, is developed and employed in the 3-D FEA code in order to numerically evaluate the material and/or structural responses. Explicit information of the relationships between the mechanical properties and material constants, which are required for the mechanical constitutive and damage evolution equations for each material, are implemented in numerical fatigue test method. The material constants selected from constitutive equations are used directly in the failure assessment of material and/or structures. The performance of the developed system has been evaluated with assessing the S-N diagram of stainless steel materials.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.8
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• pp.30-35
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• 2013

This paper describes the assessment method of deterioration condition for a power transformer using SFRA. Frequency Response Analysis(FRA) is a method to evaluate the mechanical and geometrical integrity of the core and windings within a power transformer by measuring the electrical transfer functions over a wide frequency range. SFRA is sweep frequency response analyzer for power transformer winding diagnosis. The FRA is a comparative method, that evaluates the transformer condition by comparing the obtained set of FRA results to reference results on the same, or a similar, unit. FRA techniques were widely used and much more sensitive than the traditional and internationally accepted method of impedance measurements, but that work was required on standardization and interpretation. In order to analyze the deterioration condition for power transformer, overvoltage test and mechanical distortion test were carried out. The deterioration condition for power transformer was evaluated by SFRA. It is intended to present the elemental technology of assessment method for power transformer using SFRA.

• Coupled systems mechanics
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• v.9 no.5
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• pp.433-454
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• 2020

In-place analysis for offshore platforms is essentially required to make proper design for new structures and true assessment for existing structures. The structural integrity of platform components under the maximum and minimum operating loads of environmental conditions is required for risk assessment and inspection plan development. In-place analyses have been executed to check that the structural member with all appurtenances robustness and capability to support the applied loads in either storm condition or operating condition. A nonlinear finite element analysis is adopted for the platform structure above the seabed and the pile-soil interaction to estimate the in-place behavior of a typical fixed offshore platform. The analysis includes interpretation of dynamic design parameters based on the available site-specific data, together with foundation design recommendations for in-place loading conditions. The SACS software is utilized to calculate the natural frequencies of the model and to obtain the response of platform joints according to in-place analysis then the stresses at selected members, as well as their nodal displacements. The directions of environmental loads and water depth variations have important effects on the results of the in-place analysis behavior. The result shows that the in-place analysis is quite crucial for safe design and operation of offshore platform and assessment for existing offshore structures.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.453-458
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• 2001

Pipelines have the highest capacity and are the safest and the least environmentally disruptive way for gas or oil transmission. Recently, failures due to corrosion defects have become of major concern in maintaining pipeline integrity. A number of solutions have been developed for the assessment of remaining strength of corroded pipelines. However, these solutions are known to be dependent on material properties and pipeline geometries. In this paper, a Fitness-For-Purpose type limit load solution for corroded gas pipelines made of the X65 steel is proposed. For this purpose, a series of burst tests with various types of corrosion defects are performed. Finite element simulations are carried out to derive an appropriate failure criterion. And then, further, extensive finite element analyses are performed to obtain the FFP type limit load solution for corroded X65 gas pipelines as a function of defect depth, length and pipeline geometry. And also, a window based computer program far the assessment of corrosion defect, which is named as COPAP(COrroded Pipeline Assessment Program) has been developed on the basis of proposed limit load solution.

• Nuclear Engineering and Technology
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• v.48 no.6
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• pp.1412-1422
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• 2016

Austenitic stainless steels (ASSs) are widely used for nuclear pipes as they exhibit a good combination of mechanical properties and corrosion resistance. However, high tensile residual stresses may occur in ASS welds because postweld heat treatment is not generally conducted in order to avoid sensitization, which causes a stress corrosion crack. In this study, round robin analyses on stress intensity factors (SIFs) were carried out to examine the appropriateness of structural integrity assessment methods for ASS pipe welds with two types of circumferential cracks. Typical stress profiles were generated from finite element analyses by considering residual stresses and normal operating conditions. Then, SIFs of cracked ASS pipes were determined by analytical equations represented in fitness-for-service assessment codes as well as reference finite element analyses. The discrepancies of estimated SIFs among round robin participants were confirmed due to different assessment procedures and relevant considerations, as well as the mistakes of participants. The effects of uncertainty factors on SIFs were deducted from sensitivity analyses and, based on the similarity and conservatism compared with detailed finite element analysis results, the R6 code, taking into account the applied internal pressure and combination of stress components, was recommended as the optimum procedure for SIF estimation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.587-592
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• 2005

Main transformer's integrity assessment in nuclear power plant is estimated by the electrical test of electrical core and wire and the chemical analysis of insulating oil. Mechanical test or analysis has not been so far. So this study makes it with the vibration velocity rating. The vibration velocity rating in main transformer which is based on the real data of vibration velocity measurement under operating and other machinery vibration code such as ISO code is renewed.

• Journal of the Korean Professional Engineers Association
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• v.34 no.4
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• pp.9-16
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• 2001

This paper is to represent the cross-border mobility of experienced Professional Engineers by establishing and maintaining an EMF International Register of Professional Engineers which is based on confidence in the integrity of national assessment system and a system of mutual recognition secured through continuing mutual inspection and evaluation of these systems. This paper would cover develop, monitor, maintain and promote mutually acceptable standards and criteria for facilitating the cross-border mobility of experienced Professional Engineers based on. Engineers Mobility Forum Agreement Sifted 25 June 2001, Thornybush. South Africa

• Journal of the KSME
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• v.35 no.6
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• pp.504-516
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• 1995

작년에 발생한 성수대교의 파손사고는 인적손실은 물론 경제적 그리고 사회적으로 심각한 영향을 미쳤다. 현재 수많은 공장에서 가동되고 있는 크레인 관련 시설들은 변동응력의 작용과 용접구 조물이라는 점에서 성수대교와 유사한 조건을 가지고 있다. 또한 그중에서 많은 부분은 설계시 에는 고려치 못했던 부하조건의 가혹화와 노후화 때문에 손상 가능성이 항상 존재하고 있다. 이러한 점을 고려하여 필자들은 설비의 예방정비 차원에서 크레인 거더 및 런웨이 거더의 안정성 평가에 주목하게 되었고 나름대로 얻은 경험을 지면에 정리하여 보았다.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.936-940
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• 2007

This paper is about the study on the verification method for railway system SIL which is frequency of hazard, composing Risk, one of the measurement standards for railway system safety. Frequency of hazard can be identified by using FMECA, or HAZOP, and the assessment of identified dangerous failure rate should be done by systematic methods such as FTA. Therefore, this paper provides the hazard identification level for SIL verification and the requirements necessary to verify the integrity of analysis activity.

• Journal of the Korean Arthroscopy Society
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• v.1 no.1
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• pp.31-35
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• 1997

MRI(magnetic resonance imaging) is very useful to visualize the anterior cruciate ligament (ACL) injury of the knee. Differential features of ACL injury at MRI according to acute and chronic stage should be evaluated to enable accurate assessment of the integrity or ACL. Distinguishing features of normal anatomy. acute and chronic injuries or ACL at MRI will be reviewed.