• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.4
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• pp.343-351
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• 2004

The flaw assessment method based on ${delta}_5$ parameter was recently proposed and put to the practical use. However: since it is almost impossible to measure the ${delta}_5$ by the existing commercial clip gager, we need to develope the specially designed gages which are suitable for that purpose. In this research, a double cantilever type ${delta}_5$ clip gage with the traveling distance of 4mm was developed by the finite element analysis and the construction of Wheatstone bridge circuit including strain gages. The linearity of developed ${delta}_5$ clip gage was evaluated by the MTS extensometer calibrator with the proper adapters which allow the 6s clip gage to sit on the calibrator. Consequently, the 6s clip gage revealed the good linearity between the output voltage and the traveling distance of gage.

• Computers and Concrete
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• v.21 no.3
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• pp.291-298
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• 2018

In this study, the flexural fatigue performance of concrete beams made with 100% Coarse Recycled Concrete Aggregates (RCA) and 100% Coarse Natural Aggregates (NA) were statistically commanded. For this purpose, the experimental fatigue test results of earlier researcher were investigated using two parameter Weibull distribution. The shape and scale parameters of Weibull distribution function was evaluated using seven numerical methods namely, Graphical method (GM), Least-Squares (LS) regression of Y on X, Least-Squares (LS) regression of X on Y, Empherical Method of Lysen (EML), Mean Standard Deviation Method (MSDM), Energy Pattern Factor Method (EPFM) and Method of Moments (MOM). The average of Weibull parameters was used to incorporate survival probability into stress (S)-fatigue life (N) relationships. Based on the Weibull theory, as single and double logarithm fatigue equations for RCA and NA under different survival probability were provided. The results revealed that, by considering 0.9 level survival probability, the theoretical stress level corresponding to a fatigue failure number equal to one million cycle, decreases by 8.77% (calculated using single-logarithm fatigue equation) and 6.62% (calculated using double logarithm fatigue equation) in RCA when compared to NA concrete.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.365-371
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• 2004

Generally, fracture of a material is influenced by plastic zone size developed near the crack tip. Hence, according to the relative size of plastic zone in the material, the mechanics as a tool for analyzing the fracture process are classified into three kinds, that is, Linear Elastic Fracture Mechanics, Elastic Plastic Fracture Mechanics, Large Deformation Fracture Mechanics. Even though the plastic zone size is such an important parameter, the practical measurement techniques are very limited and the one for in-situ measurement is not virtually available. Therefore, elastic-plastic FEA has been performed to estimate the plastic zone size. In this study, it is noticed that side necking at the surface is a consequence of plastic deformation and lateral contraction and the relation between the plastic zone and side necking is investigated. FEA for modified boundary layer models with finite thickness, various mode mixities $0^{\circ}$, $30^{\circ}$, $60^{\circ}$, $90^{\circ}$ and strain hardening exponent n=3, 10 are performed. The results are presented and the implication regarding to application to experiment is discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.2015-2021
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• 2000

In order to evaluate the integrity of nuclear power plant components, the analysis based on fracture mechanics is crucial. For this purpose, finite element method is popularly used to obtain J-integral. However, it is time consuming to design the finite element model of a cracked structure. Also, the J-integral should be verified by alternative methods since it may differ depending on the calculation method. The objective of this paper is to develop a three-dimensional elastic-plastic J-integral analysis system which is named as EPAS program. The EPAS program consists of an automatic mesh generator for a through-wall crack and a surface crack, a solver based on ABAQUS program, and a J-integral calculation program which provides DI (Domain Integral) and EDI (Equivalent Domain Integral) based J-integral calculation. Using the EPAS program, an optimized finite element model for a cracked structure can be generated and corresponding J-integral can be obtained subsequently.

• 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.