• 한국추진공학회지
• /
• 제16권5호
• /
• pp.67-73
• /
• 2012

고충전 탄성중합체 균열선단에서의 파괴기구를 분석하였으며, 스트립 항복 모델 및 내재결함 모델이 적용되었다. 두 가지 모델의 수정으로부터 고충전 탄성중합체에 대한 파손평가선도의 작성방법이 연구되었다. 고체로켓연료로 사용되는 고충전 탄성중합체의 인장시험 및 파괴인성시험을 수행하였으며, 시험결과로부터 파손평가선도를 작성하였다. 내재결함 모델로부터 작성한 파손평가선도는 스트립 항복 모델로부터 작성한 파손평가선도와의 비교를 위해 정규화되었다. 두 가지 모델로부터 작성한 파손평가 선도를 비교한 결과, 내재결함모델을 이용한 파손평가선도가 스트립항복모델을 이용한 파손평가선도보다 더 보수적으로 파손을 평가하는 것으로 나타났다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
• /
• pp.532-538
• /
• 2012

고충전 탄성중합체 균열선단에서의 파괴기구를 분석하였으며, 스트립 항복 모델 및 내재결함 모델이 적용되었다. 두 가지 모델의 수정으로부터 고충전 탄성중합체에 대한 파손평가선도의 작성방법이 연구되었다. 고체로켓연료로 사용되는 고충전 탄성중합체의 인장시험 및 파괴인성시험을 수행하였으며, 시험결과로부터 파손평가선도를 작성하였다. 내재결함 모델로부터 작성한 파손평가선도는 스트립 항복 모델로부터 작성한 파손평가선도와의 비교를 위해 정규화되었다. 두 가지 모델로부터 작성한 파손평가선도를 비교한 결과, 내재결함모델을 이용한 파손평가선도가 스트립항복모델을 이용한 파손평가선도보다 더 보수적으로 파손을 평가하는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
• /
• pp.181-186
• /
• 2003

There are many uncertainties in structural failures or structures, so probabilistic failure cause assessment should be performed in order to consider the uncertainties. However, in many cases of forensic engineering, the failure cause assessments are performed by deterministic approach though number of uncertainties are existed in the failures or structures. Thus, deterministic approach may have possibility for leading to unreasonable and unrealistic failure cause assessment due to ignorance of the uncertainties. Therefore, probabilistic approach is needed to complement the shortcoming of deterministic approach and to perform the more reasonable and realistic failure cause assessment. In this study, reliability-based failure cause assessment (reliability based forensic engineering) is performed, which can incorporate uncertainties in failures and structures. For more practical application, the modified ETA technique is proposed, which automatically generates the defected structural model, performs structural analysis and reliability analysis, and calculates the failure probabilities of the failure events and the occurrence probabilities of the failure scenarios. Also, for more precise reliability analysis, uncertainties are estimated more reasonably by using bayesian approach based on the experimental laboratory testing data in forensic report.

• 대한조선학회논문집
• /
• 제59권4호
• /
• pp.200-206
• /
• 2022

This study is to develop database by an experimental method for the development of condition based maintenance for auxiliary equipment in marine engine systems. Existing ships have been performing regular maintenance, so the actual measurement data development is very incomplete. Therefore, it is best to develop a database on land tests. In this paper, a database developed by an experimental method is presented. First, failure case analysis and reliability analysis were performed to select a failure mode. For the failure simulation test, a test bed for land testing was developed. The failure simulation test was performed based on the failure simulation scenario in which the failure simulation test plan was defined. A 1.5TB failure simulation database has been developed, and it is expected to serve as a basis for ship failure diagnosis and prediction algorithm model development.

• 대한기계학회논문집A
• /
• 제37권9호
• /
• pp.1169-1174
• /
• 2013

대부분의 제품은 다수의 고장모드를 가지지만, 일반적으로 신뢰성 분석에서 고장모드 별로 분석하는 경우는 많지 않다. 또는 신뢰성 분석 시 고장모드에 대한 정보를 제공하지 않거나 대표적인 고장모드로 분석하기도 한다. 특히 신뢰성 인증시험에서 가정하고 있는 형상모수는 제품의 형상모수보다는 고장모드에 대한 형상모수 값이 더 중요하다. 본 연구에서는 다수의 고장모드를 가지는 기계부품에 대한 신뢰성 분석방법으로 경쟁 고장모드 분석방법과 혼합 와이블 분석방법을 소개한다. 그리고 3 가지 고장모드를 가지는 공기압 실린더의 사례에 대해 각 고장모드 별로 형상모수를 구하였으며, 3 가지 고장모드를 고려했을 때와 하나의 고장모드로 가정했을 때의 신뢰성 측도($B_{10}$ 수명, 특성 수명)을 비교하였다.

• Structural Engineering and Mechanics
• /
• 제32권2호
• /
• pp.301-320
• /
• 2009

Damage assessment for buried structures against an internal blast is conducted by considering the soil-structure interaction. The structural element under analysis is assumed to be rigid-plastic and simply-supported at both ends. Shear failure, bending failure and combined failure modes are included based on five possible transverse velocity profiles. The maximum deflections with respect to shear and bending failure are derived respectively by employing proper failure criteria of the structural element. Pressure-Impulse diagrams to assess damage of the buried structures are subsequently developed. Comparisons have been done to evaluate the influences of the soil-structure interaction and the shear-to-bending strength ratio of the structural element. A case study for a buried reinforced concrete structure has been conducted to show the applicability of the proposed damage assessment method.

• Wind and Structures
• /
• 제34권2호
• /
• pp.161-171
• /
• 2022

This paper presents a failure type assessment curve method to judge the failure type of transmission tower segments. This novel method considers the equivalent static wind load characteristics and the transmission tower members' load-bearing capacities based on numerical simulations. This method can help judge the failure types according to the relative positions between the actual state points and the assessment curves of transmission tower segments. If the extended line of the actual state point intersects with the horizontal part's assessment curve, the segment would lose load-bearing capacity due to the diagonal members' failure. Another scenario occurs when the intersection point is in the oblique part, indicating that the broken main members have caused the tower segment to fail. The proposed method is verified by practical engineering case studies and static tests on the scaled tower segments.

• 한국안전학회지
• /
• 제23권2호
• /
• pp.37-44
• /
• 2008

The safety assessment for facility industry is now being periodically performed. For the purpose of scientific safety management, QRA(Quantitative Risk Assessment) is also being performed, and reliability data of the facilities is essential to perform the assessment. Generally, the existing safety assessment is performed by using the values announced in other industry processes, which result in the drop of reliability. In order to solve this problem, there is an urgent need to establish reliability database for the facilities. The most appropriate method is to perform a direct reliability analysis towards the facilities undergoing safety assessment. In this study, in compliance with the assessment method and procedure of OREDA-2002 handbook, the facility reliability data are collected, which include the calendar time and operational time in terms of different facility items, the number of failures in terms of different failure mode, the mean, standard deviation, lower limit and upper limit of failure rate, and the failure rate. And the data process method for this special occasion is also proposed when the number of failure is 0.

• 대한기계학회논문집A
• /
• 제23권11호
• /
• pp.2022-2032
• /
• 1999

In recent years, the subject of remaining life assessment has drawn considerable attention in the power generation industry. In power generation systems a variety of structural components, such as steam pipes, turbine rotors, and superheater headers, typically operate at high temperatures and high pressures. Thus a life prediction methodology accounting for fracture and rupture is increasingly needed for these components. For accurate failure assessment, in addition to the single parameter such as K or J-integral used in traditional fracture mechanics, the second parameter like T-stress describing the constraint is needed. The most critical defects in such structures are generally found in the form of semi-elliptical surface cracks in the welded piping-joints. In this work, selecting the structures of surface-cracked plate and straight pipe, we first perform line-spring finite element modeling, and accompanying elastic-plastic finite element analyses. We then present a framework for including constraint effects (T-stress effects) in the R6 failure assessment diagram approach for fracture assessment.

• 한국안전학회지
• /
• 제22권4호
• /
• pp.7-12
• /
• 2007

In order to evaluate the integrity of Zr-2.5Nb pressure tubes, probabilistic fracture mechanics(PFM) approach was employed. Failure assessment diagram(FAD), plastic collapses, and critical crack lengths(CCL) were used for evaluating the failure probability as failure criteria. The Kr-FAD as failure assessment diagram was used because fracture of pressure tubes occurred in brittle manner due to hydrogen embrittlement of material by deuterium fluence. The probabilistic integrity evaluation observed AECL procedures and used fracture toughness parameters of EPRI and recently announced theory. In conclusion, the probabilistic approach using the Kr-FAD made it possible to determine major failure criterion in the pressure tube integrity evaluation.