• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1988년도 학술세미나 강연집
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• pp.3-67
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• 1988

Model studies on the response of homgeneous earth embankment dams subjected to strike-slip fault movement have been penomed via centrifuge and finite element analysis. The centrifuge model tests have shown that crack development in earth embankment experiences two major patters: shear failure deep inside the embankment and tension failure near the surface. The shear rupture zone develops from the base level and propagates upward continuously in the transverse direction but allows no open leakage chnnel. The open tensile cracks develop near the surface of the embankment, but they disappear deep in the embankment. The functional relationship has been developed based on the results of the centrifuge model tests incorporating tile variables of amount of fault movement, embankment geometry, and crack propagation extent in earth des. This set of information can be used as a guide line to evaluate a "transient" safety of the duaged embankment subjected to strike-slip fault movement. The finite element analysis has supplemented the additional expluations on crack development behavior identified from the results of the centrifuge model tests. The bounding surface time-independent plasticity soil model was employed in the numerical analysis. Due to the assumption of continuum in the current version of the 3-D FEM code, the prediction of the soil structure response beyond the failure condition was not quantitatively accurate. However, the fundamental mechanism of crack development was qualitatively evaluated based on the stress analysis for the deformed soil elements of the damaged earth embankment. The tensile failure zone is identified when the minor principal stress of the deformed soil elements less than zero. The shear failure zone is identified when the stress state of the deformed soil elements is at the point where the critical state line intersects the bounding surface.g surface.

• 대한기계학회논문집A
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• 제20권9호
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• pp.2819-2832
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• 1996

The estimation of the remaining life for the aged components in power plant as well as chemical and petroleum plants has been recently concerned. The raw materials used in this study are the 1Cr-1Mo-0.25V steel which intensified P and S compositions along with the nominal compositions of ASTM A 470 standard. Five kinds of specimens with the different degradation levels were prepared by isothermal aging heat treatment at 630.deg.C. The mechanical properties and rotated bending fatigue strength of virgin and aged 1Cr-1Mo-0.25V steel have been investigated through the hardness, tensile, fatigue test, SEM fractograph and EDS analysis at 538.deg.C and room temperature, respectively. Thus the data of aged specimens were compared with those of virgin specimen to evaluate the aging effects. The main results obtained in this study are as follows ; The decrease of the yield and tensile strength due to degradation was distinguished until 50, 000hrs simulated service time. And it was confirmed that the considerable amount of P, Mn, Cr and S was precipitated at the grain boundary of aged material through the SEM and EDS analysis. The rotated bendingd fatigue strength at 538.deg.C of virgin, 25, 000, 50, 000, 75, 000 and 100, 000 hrs aged material was decreased 44.6 %, 49.6 %, 51.5 %, 52.4% and 53.8% than that of virgin material at 10$_{7}$cycles of room temperature, respectively. The major cracks of virgin and aged materials mainly initiated at the inclusions including Si, P and Mn compositions which were located at the outer periphery of the specimen.n.

• 한국의류학회지
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• 제14권4호
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• pp.262-273
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• 1990

The purpose of this study is to investigate the softening effect of cellulase-treated cotton fabric and the damage on the fabric which is accompanied by the treatemnt. Cotton fabric is treated with cellulase under various concentrations and time, and the weight loss, hand values (by KES), surface characteristics, moisture regain, tensile strength, copper number and intrinsic viscosity of the treated samples and untreated samples have been compared. The results are as follows: 1. The weight loss of cotton fabric increased as the concentration of cellulase and the treating time increased. 2. The enzyme treatment had little effect on the stiffness of the treated samples but anti- drape stiffness decreased for the treated samples. Fullness and softness of the treated samples increased and crispness decreased with the lowest level reaching after two hours of the treatment for all concentrations. Scrooping feeling of the treated samples increased and flexibility with soft feeling increased as the treating time and the concentration of cellulase increased. 3. Moisture regain of the samples decreased as the treating time and the concentration of the enzyme increased and the treated fabric showed cracks on the fiber surface, and much surface fibers on the fabric have been removed after the treatment. 4. Tensile strength of the samples decreased as the treating time and as the concentration of cellulase increased, and the copper number increased while the intrinsic viscosity decreased as the treating time increased, but cellulase concentration had a little effect.

• 한국의류학회지
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• 제33권2호
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• pp.213-221
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• 2009

This study provides the optimum papain treatment method and its effect on wool/polyester blend fabrics. The enzymatic treatment condition is optimized depending on its pH level, temperature, concentration of enzyme, treatment time and concentration of activators. The characteristics of samples treated with the papain are measured using weight loss, tensile strength, whiteness, WCA, dyeing property and surface micrographs. The results are described as follows: According to measuring weight loss, tensile strength and whiteness, a pH level of 7.5, $70^{\circ}C$, 10% papain(o.w.f.) and 60minutes of treatment time are optimized for papain treatment. L-cysteine and sodium sulfite are able to activate the papain. The optimum concentrations of them are 10mM and 50mM respectively. The WCA of fabrics is decreased since papain treatment makes wool/polyester blend fabrics more hydrophilic. Scouring with papain treatment improves whiteness and dyeing property of fabrics. The dyeing property of papain-treated fabrics is enhanced simply by a single step dyeing process using a basic dye. The surface of wool treated with papain in the presence of L-cysteine shows to be descaled. The surface of wool fibers in the presence of sodium sulfite, however, shows it is hydrolyzed evenly instead of being descaled. The surface of papain treated polyester fibers shows cracks and voids.

• 한국농공학회지
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• 제34권2호
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• pp.49-59
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• 1992

In our researches we made mix-design, with the mixing ratio and pre-cracked ratio of steel fibrous different from each other, building the steel fibrous concrete beam which had pre-cracks. To obtain the fracture characteristics of steel fibrous reinforced concrete, series of experiment were conducted on pre-cracked beam subjected to 3-point bending. Thus, we carried out experiments on the destructive characteristics of its pre-crack and post-crack and the result is as follows. 1. The compressive strength of steel fibrous concrete beam increased more slightly than plane beam, and the tensile strength increased 37%, 59%, 94% and 121% respectively when the amount of fibrous was 0.5%, 0.1% 1.5%, and 1.75% respectively. 2. As the amount of steel fibrous mixing increased ant the steel fibrous inhibited the crack growth, the crack condition of steel fibrous concrete beam was retarded irregularly, and this increased fracture load. 3. The defiance of destruction was reduced in the ratio of 1.35 times and 1.22 times respectively when the length of pre-crack was each 2cm and 4cm in comparison with the case of being without the length, and was similar to that of plane beam when the amount of steel fibrous mixing was below 1.0%, and increased linearly when it as above 1.0%. 4. The experimental formula seeking fracture energy was follows and thus we found that the value of fracture energy depended upon tensile strength and the size of speciment. $G_f=K\;{\cdot}\;f_f^'{\cdot}$da/Ec 5. We observed that in the load-strain curve of steel fibrous concrete beam the progress of the crack became slow, compared with plane beam because the crack condition became long to the extent of about 10 times. Concrete was faultiest brittleness fracture through the study, it was known ductile.

• Journal of Welding and Joining
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• 제2권1호
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• pp.30-40
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• 1984

Moisture content in the coating of an electrode is known to cause defects such as porosities, fish eyes and cracks in the weld metal, however, quantitative relationship between them is not clearly understood. In this study widely consumed and the most common type of arc welding rods such as ilmenite and low hydrogen type were chosen for the investigation, and attempts were made to correlate the relationship between the mechanical properties and gas contents when welding was carried out with electrodes of various moisture contents. As the relative humidity changed from 70% to 92%, it was determined that moisture content to reach saturation was in the range of 0.6~6.8%. As the moisture content in the electrode coating was increased, the amount of gaseous components (H, O, N) in the weld metal was accordingly increased, especially diffusible hydrogen showed prominent effect, i.e. it increased proportionally to the increase of the moisture content. The mechanical properties of the weld metal was observed to become more inferior as the diffusible hydrogen was greater. It was determined for ilmenite type of electrode that the increase of hydrogen content was approximately 1.8ml per unit weight percent increase of moisture and also tensile strength resulted lowering from $45.3kg/\textrm{mm}^2$ to $42.7kg/\textrm{mm}^2$ as moisture content increased from 0.7% to 6.8%. For low hydrogen type the increase of the hyrogen was about 2.4ml per unit percent of moisture and tensile strength decreased from $63.0kg/\textrm{mm}^2$ to $53.8kg/\textrm{mm}^2$ particularly in the region of moisture content 0.1~4.2%.

• 대한토목학회논문집
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• 제7권2호
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• pp.69-77
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• 1987

철근 콘크리트 구조물의 재료적 비선형 해석을 위해 유한요소법을 적용하였다. 2 축응력 상태에서의 콘크리트 거동은 인장균열과 균열사이의 인장증강효과(tension stiffening effect) 그리고 최대압축 강도를 넘어서의 변형연화(strain-softening) 효과를 고려하는 비선형 구성 방정식으로 나타냈다. 콘크리트를 직교성 (orthotropic) 재료로 가정함으로써 비선형 탄성체로 간주하고, 등가일축변형도 개념을 사용한 등가 일축 응력-변형도(equivalent uniaxial stress-strain) 관계식으로 모형화하고, 철근 보강재는 Bauschinger 효과를 갖는 탄소성 변형 경화재료(elasto-plastic strain-hardening material)로 모형화 했다. 평면 응력 상태에서 철근콘크리트 보의 모형화는 각 절점에 2 개의 자유도를 갖는 사각형요소로 모형화하여 적용 시쳤으며, 이로부터 구한 유한요소해석의 결과치를 실험결과치의 중앙처짐, 응력, 변형율 그리고 균열성장과정에 대하여 비교 검토 하였다.

• 한국지진공학회논문집
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• 제6권4호
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• pp.7-13
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• 2002

지진하중을 받는 철근콘크리트 패널의 이력거동을 힘의 평형조건, 변형의 적합조건 및 재료의 구성법칙을 이용한 재료메카니즘을 이용하여 예측하였다. 해석에서는 7단계의 압축응력-변형률곡선과 6단계의 인장응력-변형률곡선으로 구성된 콘크리트의 응력-변형률 모델을 이용하였다. 콘크리트의 응력-변형률 모델에는 균열이 발생한 콘크리트의 연화효과에 의한 압축강도 저감효과가 고려되었다. 해석에 적용된 반복하중을 받는 철근의 평균 응력-변형률관계에는 바우싱거효과 및 철근과 콘크리트의 부착작용을 고려한 인장경화효과가 고려되었다. 해석에 의하여 예측된 패널의 이력거동은 철근비가 다른 3개의 철근콘크리트 패널시험에 의하여 검증되었다. 해석법은 패널의 이력곡선을 추적하여 철근비가 점차 증가하는 시험체의 최대전단응력을 매우 정확히 예측하였다. 또한, 해석에 의하여 예측된 수직 및 수평변형률은 실험에서 관찰된 변형률과 잘 일치하였다.

• Structural Engineering and Mechanics
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• 제60권6호
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• pp.1063-1077
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• 2016

Components manufactured from composite materials are frequently subjected to superimposed mechanical and thermal loadings during their operating service. Both types of loadings may cause fracture and failure of composite structures. When composite cross-ply laminates of type [$0_m/90_n]_s$ are subjected to uni-axial tensile loading, different types of damage are set-up and developed such as matrix cracking: transverse and longitudinal cracks, delamination between disoriented layers and broken fibers. The development of these modes of damage can be detrimental for the stiffness of the laminates. From the experimental point of view, transverse cracking is known as the first mode of damage. In this regard, the objective of the present paper is to investigate the effect of transverse cracking in cross-ply laminate under thermo-mechanical degradation. A Finite Element (FE) simulation of damage evolution in composite crossply laminates of type [$0_m/90_n]_s$ subjected to uni-axial tensile loading is carried out. The effect of transverse cracking on the cross-ply laminate strength under thermo-mechanical degradation is investigated numerically. The results obtained by prediction of the numerical model developed in this investigation demonstrate the influence of the transverse cracking on the bearing capacity and resistance to damage as well as its effects on the variation of the mechanical properties such as Young's modulus, Poisson's ratio and coefficient of thermal expansion. The results obtained are in good agreement with those predicted by the Shear-lag analytical model as well as with the obtained experimental results available in the literature.

• Geomechanics and Engineering
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• 제17권4호
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• pp.355-365
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• 2019

It is normal to observe the presence of numerous cracks in coal body. And it has significantly effective on the mechanical characteristics and realistic failure models of coal mass. Therefore, this paper is to investigate the influence of crack parameters on coal body by comprehensive using theoretical analysis, laboratory experiments and numerical simulation through prepared briquette specimens. Different from intact coal body possessing single peak in stress-strain curve, other specimens with crack angle can be illustrated to own double peaks. Moreover, the unconfined compressive strength (UCS) of specimens decreases and follow by increasing with the increase of crack angle. It seems to like a parabolic shape with an upward opening. And it can be demonstrated that the minimum UCS is obtained in crack angle $45^{\circ}$. In terms of failure types, it is interesting to note that there is a changing trend from tensile failure to tensile-shear mixing failure with tension dominant follow by shear dominant with the increase of crack angle. However, the changing characteristics of UCS and failure forms can be explained by elastic-plastic and fracture mechanics. Lastly, the results of numerical simulations are good consistent with the experimental results. It provides experimental and theoretical foundations to reveal fracture mechanism of coal body with non-penetrating single crack further.