• Journal of the Korean Society of Industry Convergence
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• v.9 no.2
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• pp.117-122
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• 2006

This paper is to provide some of the analysis procedures of the FAD(Failure Assessment Diagram), which is applied th the safety test of the atomic pressure vessels and other structures. Harrison proposed R-6 Diagram, and Bloom developed the method of DPFAD(Deformation Plasticty Failure Assessment Diagram). Analysis of J-integration of the plastic materials give the failure test curve for the materials with serious work hardening effect. J value was obtained form both FEM(Finite Element Mothod) and the experiment using compact type specimen for J=JIC, and the results were compared. In this study, the results of analysis using DPFAD and the factors affecting DPFAD in Static fatigue and fracture were reviewed. It was shown that the concept of DPFAD can be applied to test the safety of the structures.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.646-655
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• 1990

A practically useful system for elastic-plastic fracture mechanics analysis has been developed. The developed system is comprised of the deformation plasticity failure assessment diagram(DPFAD) approach and the J-integral/Tearing modulus(J/T) approach. The system contains analysis routines for five types of fracture specimens : compact tension, center cracked tension, single edge craked plate in uniform tension, single edge cracked plate in three point bending and double edge cracked plate in tension. A double interpolation scheme was adopted to interpolate J values from the EPRI developed EPFM handbook and the Newton-Raphson method was used to obtain proper loadings for displacement control conditions. A graphic output system was utilized to present numerical results. Several case studies were performed to evaluate the accuracy and the usefulness of the code. It was found that the J/T approach and the DPFAD approach yielded similar results. However, the DPFAD approach is more convenient for qick assessment of integrity of cracked structures while the J/T approach is more useful in evaluating the full history of the fracture process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1187-1194
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• 2009

During the last decade, possibility of flaw occurrences has been rapidly increased world-widely as the increase of operating times of petro-chemical facilities. For instance, from a recent in-service inspection, three different sized surface cracks were detected in welding parts of a spherical oxygen holder in Korea. While API579 code provides corresponding engineering assessment procedures to determine crack driving forces, in the present work, numerical analyses are carried out for the cracked oxygen holder to investigate effects of complex geometry, analysis model and residual stress. With regard to the detailed finite element analysis, stress intensity factors are determined from both the full three-dimensional model and equivalent plate model. Also, as an alternative, stress intensity factors are calculated for equivalent plate model by employing the noted influence stress function technique. Finally, parametric structural integrity evaluation of the cracked oxygen holder is conducted in use of failure assessment diagram method, J/T method and DPFAD method. Effects of the geometry and so forth are examined and key findings from the simulations are fully discussed, which enables to determine practical safety margins of spherical components containing a defect.

• Journal of the KSME
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• v.31 no.3
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• pp.244-250
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• 1991

본 글에서는 EPFM을 이용한 구조물의 건전성 평가법을 소개하였다. 이러한 방법을 원자력발 전소 NSSS평가에 적용하면 좀 더 정확한 해석결과를 얻을 수 있으며 불필요한 가동중단이나 보수작업을 피할 수 있다. 한편 ASME XI에서 현재 제정중인 EPFM 관련법규도 소개하였는데, 가까운 장래에 결정될 최종안에는 약간의 내용변화가 있으리라 생각된다. 근래에는 건전성평 가를 위한 컴퓨터 소프트웨어가 많이 개발되어 이용되고 있다. 필자들이 아는 바로는 B & W 사에서 개발한 DPFAD, Structural Integrity Associate 사에서 개발한 PC-CRACK, 그리고 LBB 설계용으로 EPRI에서 개발한 FLET등이 있다. 국내에서는 필자들에 의해 개발된 EPIES가 있 는데 자세한 내용은 관련문헌(10,11)을 참고하기 바란다. 본 글에서 소개한 EPEM 평가법은 원 자력 발전소뿐만 아니라 가동온도가 높고 연성재료가 널리 사용되는 화력 발전설비, 석유, 화 학설비 및 제철설비 등에도 공통적으로 적용될 수 있다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.6
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• pp.1798-1809
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• 1996

The purpose of this paper is to develop new Z-Factors to evaluate the behavior of circumferential surface crack in ferritic steel piping including base metal and Submerged Arc Weld(SAW) metal in nuclear power plant. The Z-factor is a load multiplier to convert plastic load to elasto-plastic load. However the current Z-Factor is a load multiplier to convert plastic load to elasto-plastic load. However the current Z-Factor gives too conservative results. In this study, a J-estimation method, SC.TNP method, which is based on GE/EPRI expression, is used to develop new Z-Factors. The desirabilities of both the SC.TNP mehtod and the new Z-Factors are examined using the previous experimental results for the circumferential surface crack in ferritic steel pippings. The results are as follows ; (1) The SC.TNP mehtod is good for describing the circumferential surface crack behavior in farritic steel pipings, while the well-known R6 mehtod and DPFAD method give too conservative results. (2) The ASME-Z-Factor method using nwe Z-Factors well predicts the behavior of circumferential surface crack in ferritic steel pipings including base emtal and SAW metal.