• 대한기계학회논문집A
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• 제24권12호
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• pp.2917-2925
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• 2000

Tensile strength and failure process of composite materials depend on the variation in fiber strength, matrix properties and fiber-matrix interfacial shear strength. A Monte-Carlo simulation considering variation in these factors has been widely used to analyze such a complicated phenomenon as a strength and simulated the failure process of unidirectional composites. In this study, a Monte Carlo simulation using 2-D and 3-D(square and hexagonal array) model was performed on unidirectional graphite/epoxy and glass/polyester composites. The results simulated by using 3-D hexagonal array model have a good agreement with the experimental data which were tensile strength and failure process of unidirectional composites.

• Structural Engineering and Mechanics
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• 제55권5호
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• pp.979-999
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• 2015

This paper proposes a novel reliability analysis method which computes reliability index, most probable point and probability of failure of uncertain systems more efficiently and accurately with compared to Monte Carlo, first-order reliability and response surface methods. It consists of Initial and Simulation steps. In Initial step, a number of space-filling designs are selected throughout the variables space, and then in Simulation step, performances of most of samples are estimated via interpolation using the space-filling designs, and only for a small number of the samples actual performance function is used for evaluation. In better words, doing so, we use a simple interpolation function called "reduced" function instead of the actual expensive-to-evaluate performance function of the system to evaluate most of samples. By using such a reduced function, total number of evaluations of actual performance is significantly reduced; hence, the method can be called Reduced Function Evaluations method. Reliabilities of six examples including series and parallel systems with multiple failure modes with truncated and/or non-truncated random variables are analyzed to demonstrate efficiency, accuracy and robustness of proposed method. In addition, a reliability-based design optimization algorithm is proposed and an example is solved to show its good performance.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.309-314
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• 1999

In this paper, an application of finite element procedure fur tunnel failure analysis has been studied. The numerical model is applied to the simulation of a series of plane strain laboratory tests on the small scale model of a shallow tunnel. By comparing experimental and numerical results some conclusions are drawn on the effectiveness of the numerical approach. The findings from these numerical experiments show relative differences in the pattern of failure behaviour for shallow tunnels.

• 한국터널지하공간학회 논문집
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• 제15권4호
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• pp.387-400
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• 2013

본 연구에서는 터널 갱구사면을 대상으로 사면안정성 및 산사태 위험도를 평가하였다. 먼저 사면안정성 해석을 통해 붕괴위험도가 가장 높은 구간을 선정하고 구체적인 붕괴규모를 파악하였다. 해석결과 해발고도 485~495 m인 구간은 강우시 안전율이 0.99로 불안정한 상태로 나타났다. 이 때 붕괴심도는 최대 2.1 m이며 붕괴 길이는 사면의 경사방향으로 18.6 m로 분석되었다. 해당구간에서 사면붕괴 시 파생되는 사태물질의 이동특성을 실시간으로 분석하고 터널 갱구부에 미치는 영향을 파악하고자 산사태 시뮬레이션 해석을 수행하였다. 해석결과 사태물질은 7.74 m/sec의 평균속도를 보이며 주로 계곡부를 따라 산 하부로 이동하는 것으로 분석되었다. 사태물질은 산 하부로 갈수록 점차 확산되며 10초 후에 터널 갱구부 위를 지나고 20.2초 후에 산하부에 도달하는 것으로 분석되었다. 특히 터널 갱구부는 사태물질 이동경로의 중심부에 위치하고 있어 산사태 발생 시 직접적인 피해를 받는 것으로 나타났다.

• 한국터널지하공간학회 논문집
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• 제9권3호
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• pp.263-273
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• 2007

일반적으로 고심도에 건설되는 암반구조물의 경우 높은 현지응력과 공동의 굴착에 따른 유도응력으로 인하여 공동 경계면에서 스폴링(spatting)이나 슬래빙(slabbing)과 같은 취성파괴가 발생할 수 있다. Hoek-Brown과 Mohr-Coulomb 파괴기준과 같은 전통적인 파괴기준을 적용한 결과 취성파괴현상과 파괴심도 등을 예측할 수 없는 것으로 나타나 취성파괴를 예측하기 위한 여러 모델이 제안되었으며, 그 중 CWFS 모델이 적합한 것으로 알려져 있다. 본 연구에서는 모형실험에서 얻어진 원형공동주변의 취성파괴현상을 모델링하기위하여 CWFS 모델을 적용하였으며, 입력자료의 산정을 위해 암석의 손상정도와 손상에 따른 물성의 변화를 측정하는 손상제어시험을 수행하였다. CWFS 모델에 의해 예측된 파괴양상을 전통적인 파괴기준에 의한 해석결과 및 모형실험결과와 비교하여 취성파괴모델링의 적용성을 평가하였다.

• 한국시뮬레이션학회논문지
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• 제25권4호
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• pp.109-115
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• 2016

본 연구는 철도기관사에 의해 유발되는 사고와 우울감 및 인지실패 간의 관계를 '우울감 ${\rightarrow}$ 인지실패 ${\rightarrow}$ 사고'의 인과관계로 접근하는 연구모형 1과 '사고 ${\rightarrow}$ 우울감 ${\rightarrow}$ 인지실패'의 인과관계로 접근하는 연구모형 2로 설정하고 어느 모형이 타당한지를 구조방정식 모형으로 검증하였다. 현직 철도기관사 416명의 설문응답 유효데이터를 토대로 검증한 결과 후자의 연구모형, 즉 '사고 ${\rightarrow}$ 우울감 ${\rightarrow}$ 인지실패'의 인과관계에서 사고가 우울감을 매개로 하여 사고에 영향을 미친다는 점에서 모형 2가 통계적으로 타당하다는 결론을 도출하였다. 이 같은 연구결과는 인적오류와 관련하여 사고와 우울감의 인과관계 측면에서 접근하고 제도적인 개선방안을 함께 모색할 때 궁극적으로 기관사의 실수와 인지실패를 저감시킴으로써 인지실패로 인한 사고와 인적 오류의 확률을 그만큼 저감할 수 있다는 것을 시사한다.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2003년도 추계학술대회 및 정기총회
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• pp.147-151
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• 2003

Yield enhancement in semiconductor fabrication is important. Even though DRAM yield loss may be attributed to many problems, the existence of defects on the wafer is one of the main causes. When the defects on the wafer form patterns, it is usually an indication for the identification of equipment problems or process variations. In this paper describes the techniques to automatically classify a failure pattern using a fail bit map.

• International Journal of Precision Engineering and Manufacturing
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• 제1권2호
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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.

• 한국해양공학회지
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• 제28권1호
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• pp.34-46
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• 2014

This paper discusses a new formulation for the failure strain in the average stress triaxiaility domain for a low-temperature high-strength steel (EH36). The new formula available at a low average stress triaxiality zone is proposed based on the comparison of two results from tensile tests of flat type specimens and their numerical simulations. In order to confirm the validity of the failure strain formulation, a user-subroutine was developed using Abaqus/Explicit, which is known to be one of the most popular commercial finite element analysis codes. Numerical fracture simulations with the user-subroutine were conducted for all the tensile tests. A comparison of the engineering stress-strain curves and engineering failure strain obtained from the numerical simulation with the user-subroutine for the tensile tests revealed that the newly developed user-subroutine effectively predicts the initiation of failure.

• Structural Engineering and Mechanics
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• 제30권2호
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• pp.177-190
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• 2008

Material failure behavior is generally dependent on loading rate. Especially in brittle and quasi-brittle materials, rate dependent material behavior can be significant. Empirical formulations are often used to predict the rate dependency, but such methods depend on extensive experimental works and are limited by practical constraints of physical testing. Numerical simulation can be an effective means for extracting knowledge about rate dependent behavior and for complementing the results obtained by testing. In this paper, the failure behavior of a brittle material under different loading rates is simulated by molecular dynamics analysis. A notched specimen is modeled by sub-million particles with a normalization scheme. Lennard-Jones potential is used to describe the interparticle force. Numerical simulations are performed with six different loading rates in a direct tensile test, where the loading velocity is normalized to the ratio of the pseudo-sonic speed. As a consequence, dynamic features are achieved from the numerical experiments. Remarkable failure characteristics, such as crack surface interaction/crack arrest, branching, and void nucleation, vary in case of the six loading cases. These characteristics are interpreted by the energy concept approach. This study provides insight into the change in dynamic failure mechanism under different loading rates.