• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.993-1000
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• 2002

The objective of this work is to develop the capability to analyze accurately the mixed-mode propagation of a crack in composite structures with elastic orthotropic material stiffness properties and anisotropic material strength characteristics. In order to develop the capability to fully analyze fracture growth and failure in anisotropic structures, we examined the fundamental problem of mixed mode fracture by carrying out the analysis on orthotropic materials with an inclined crack subject to biaxial loading. Our goal here is to include an additional term in the asymptotic expansion of the crack tip stress field and to show that the direction of crack initiation can be significantly affected by that term. We employ the normal stress ratio theory to predict the direction of crack extension. It is shown that the angle of crack extension can be altered by horizontal loads and the use of second order term in the series expansion is important f3r the accurate determination of crack growth direction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.11
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• pp.3498-3506
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• 1996

A loading device to be used in fracture experiment is presented. It's loading angle can be adjusted from $-45^{\circ}$ to $105^{\circ}$ at intervals of $15^{\circ}$ for a CTS ( compact tension-shear) specimen, so that it is to be useful to measure mixed mode toughness. The equations to give the $K_ I$, $K_ I1$ and J-integral for the experiment are evluated though finite elemetn analysis in which the loading procedure is simulated and the behaviors of the specimen such as load-displacement curve are estimated. In the course of the evaluation the values $K_ I$, $K_ I1$ and J-integral calculated through recentrly released numerical methods are employed as the reference ones.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.733-738
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• 2000

It is difficult to obtain accurate fracture toughness values by RILEM committees proposed three point bend test(TPB) because the shape of load-deflection curve is irregular and final crack propagation occurs after some slow stable cracking. However, for disk test, fracture toughness is easily obtained from crack initial load. We examined the cracked high strength concrete disk and the experimental results were compared with the results by finite element analysis(FEA). Also we compared experimental fracture locus with theoretical fracture locus.

• Nuclear Engineering and Technology
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• v.52 no.8
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• pp.1732-1741
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• 2020

The structural integrity of welded joints in the reactor pressure vessel (RPV) is directly related to the safety of nuclear power plants. The RPV is made from SA508-III steel in a pressurized water reactor. In this study, we investigated the effects of temperature on the tensile and fracture toughness properties of Chinese SA508-III welded joint in different sampling areas in order to provide reference data for structural integrity assessments of RPVs. The specimens used in tensile and fracture toughness tests were fabricated from the base metal (BM), weld metal (WM), and the heat-affected zone (HAZ) in the welded joint. The representative testing temperatures included the ambient temperature (20 ℃), upper shelf temperature (100 ℃), and service temperature (320 ℃). The results showed that temperature greatly affected the fracture toughness (JIC) values for the SA508-III welded joint. The JIC values for BM and HAZ both decreased remarkably from 20 ℃ to 320 ℃. The fracture morphologies showed that the BM and HAZ in the welded joint exhibited fully ductile fracture at 20 ℃, whereas partial cleavage fracture was mixed in ductile fracture mode at 100 ℃ and 320 ℃. The WM exhibited the ductile and cleavage fracture mixed mode at various temperatures, and the JIC values showed slight changes.

• Steel and Composite Structures
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• v.50 no.2
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• pp.237-247
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• 2024

Research on interfacial crack formation in orthotropic bi-materials has experienced a notable increase in recent years, driven by growing concerns about structural integrity and reliability. The existence of a crack at the interface of bi-materials has a substantial impact on mechanical strength and can ultimately lead to fracture. The primary objective of this article is to introduce a comprehensive analytical model and establish stress relationships for investigating interfacial crack between two non-identical orthotropic materials with desired crack-fiber angles. In this paper, we present the application of the Interfacial Maximum Tangential Stress (IMTS) criterion, in combination with the Reinforcement Isotropic Solid (RIS) model, to investigate the behavior of interfacial cracks in orthotropic bi-materials under mixed-mode I/II loading conditions. We analytically characterize the stress state at the interfacial crack tip using both Stress Intensity Factors (SIFs) and the T-stress term. Orthotropic materials, due to their anisotropic nature, can exhibit complex crack tip stress fields, making it challenging to predict crack initiation behavior. The secondary objective of this study is to employ the IMTS criterion to predict the crack initiation angle and explore the notable impact of the T-stress term on fracture behavior. Furthermore, we validate the effectiveness of our approach in evaluating Fracture Limit Curves (FLCs) for interfacial cracks in orthotropic bi-materials by comparing our FLCs with relevant experimental data from existing literature.

• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.28-36
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• 1999

In this paper, A circular arc crackered plate in biaxially stretched sheets was investigated in the boundary element method. The applications of fracture mechanics have traditionally concentrated on crack problems under an mode I, straight crack. However, many service failures occur from growth of cracks subjected to mixed mode loadings. A rectangular plate with arc crack or slanted central crack, under biaxial tensile loading, was treated analytically and also solved numerically. The Results from BEM applying different loading conditions, crack length (a/W), arc angle($\alpha$) are presented and discussed. The stress intensity factors are evaluated by the techniques of the J-integral. The decomposition method, used to decouple the stress intensity factors in mixed mode problems, is implemented by a considering a small circular contour path around each crack tip. The BIE method was successfully applied to a circular arc crackerd plate problem, also slanted centre cracked plate under mixed mode.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1754-1759
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• 2007

Propagation of a mixed-mode crack in Soda-Lime silica glass using Movable Cellular Automata (MCA) method is demonstrated in this study. In MCA method, special fracture criterion is used to describe the process of crack initiation and propagation. Comparison between MCA and other crack initiation criteria results are made. The crack resistance curves and bifurcation angles under different loading angles are found. In comparisons with results of maximum circumferential tensile stress criterion, MCA result showed the sufficient agreement.

• International Journal of Safety
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• v.2 no.1
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• pp.1-6
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• 2003

In this paper, several different fracture criteria using the Eftis and Subramanian's stress solutions [1] are compared with the printed experimental results under different loading conditions. The analytical results of using the solution with non-singular term show better than without non-singular in comparison with the experimental data. And maximum tangential stress criterion (MTS) and maximum tangential strain energy density criterion (MTSE) can get useful results for several loading conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.491-497
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• 2015

This paper reports an experimental study for evaluating the effect of temperature on the mode I, mode II and mixed-mode interlaminar fracture toughness of adhesive joints with a curved cross-section of filament-wound dome-separated composite pressure vessel. Mode I and mixed-mode interlaminar fracture toughness were evaluated using DCB specimens, while mode II interlaminar fracture toughness was determined using ENF specimens. $[{\pm}10^{\circ}]_6$, $[{\pm}27^{\circ}]_6$ and ($[{\pm}10^{\circ}]_3/FM73/[{\pm}27^{\circ}]_3$) winding specimens with the curved cross-section were considered. In-situ temperature environments were simulated with a range of $-30^{\circ}C-60^{\circ}C$ using an environmental chamber and furnace. Experimental results on the effect of temperature indicate that interlaminar fracture toughness tends to be high at low temperature and is degraded with increase in temperature. For specimen types, it was found that interlaminar fracture toughness of $[{\pm}10^{\circ}]_3/FM73/[{\pm}27^{\circ}]_3$ winding specimens considered as adhesive joints of dome and helical part was higher than other specimens.

• 연구논문집
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• s.22
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• pp.115-125
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• 1992

Mechanical properties and microstructure were investigated on vacuum induction melted $Fe_3A1$base alloys of $DO_3$ structure. Specal emphasis were put on the effect of alloy chemistry, grain size and process(rolling, directional solidification) on mechanical properties of Fe-22.5-39at.%Al at elevated temperature between room temperature and $800^{\circ}C$. grain size of as-cast alloys is refined by rolling from 1mm to $80\mum$. Tensile strength of Fe-24.lat.%AI was about 404MPa at the critical ordering temperature, and the fracture strain of the alloy was 1-2% at room temperature. An inverse temperature dependence of the strength is noticed as-cast $Fe_3A1$. The presence of Cr and Zr do not affect the room temperature ductility and high temperature strength. Fracture strain of directionally solidified(DS) $Fe_3A1$ is about 1%at room temperature, but is about 60%at. $T_C$(550^{\circ}C)$. Tensile strength of DS alloy is lower than that of as-cast alloy at $530^{\circ}C$ and $430^{\circ}C$. Failure mode at room temperature varies from transgranular fracture to intergranular fracture with the addition of Al. the failure mode also varies from mixed(transgranular+ intergranular) mode between room temperature and $500^{\circ}C$ to intergranular mode above $550^{\circ}C$