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  • Title/Summary/Keyword: 유도 경화

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Finite element analysis of unconstrained axisymmetric piercing (구속이 없는 축대칭 피어싱 공정의 유한요소해석)

  • 양동열;유요한;이종수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.10 no.6
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    • pp.876-888
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    • 1986
  • The Study is concerned with the analysis of unconstrained axisymmetric piercing as a nonsteady forging process by the rigid-plastic finite element method. In the numerical analysis of axisymmetric piercing, the initial velocity field is generated by assuming the material as a linear viscous material to begin with in order to facilitate the input handling and to ensure better convergencey. The strain-hardening effect for nonsteady deformation and the friction of the die-material interial interface are considered in the formulation. Rigid body treatment is also incorporated in the developed program. The experiments are carried out for aluminum alloy specimens (A1204) with different specimen heights. It is shown that the experimental results are in excellent agreement with the finite element simulations is deformed configuration. For load prediction the theoretical prediction shows excellent agreement with th eexperimental laod in the initial stage of loading before fracture of the specimen is not initiated. Distribution of stresses, strains and strain rates has been found for the given cases in computation. On this basis several fracture criteria are introduced in order to check the fracture initiation. It is found that maximum shear criterion is capable of good fracture prediciton.

Thermal Stability of Glass Powder and Rubber-Filled Phenolic Resins and Dynamic Mechanical Properties of Glass Braid/Phenolic Composites (유리분말 및 고무 충진 페놀수지의 열안정성 및 Glass Braid/페놀수지 복합재료의 동역학적 열특성)

  • Yoon, Sung Bong;Cho, Donghwan;Lee, Geon-Woong
    • Journal of Adhesion and Interface
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    • v.8 no.4
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    • pp.14-22
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    • 2007
  • In the present study, the effect of milled glass powder and liquid-type nitrile rubber (NBR) on the thermal stability of phenolic resin and the dynamic mechanical properties of glass braid/phenolic composites has been investigated by means of thermogravimetric analysis and dynamical mechanical analysis. It was found that both milled glass power and NBR filled in the waterborne phenolic resin significantly influenced the thermal stability of phenolic resins and the storage modulus and tan delta of the composites. The presence of glass powder increased the thermal stability of the phenolic resin, whereas the presence of NBR resulted in the weight loss in the specific temperature range. The thermal stability of the phenolic resins without and with the fillers was dependent not only on the cure temperature but also on the cure time. The variation of the storage modulus and tan δ of strip-type glass braid/phenolic composites was also influenced with the introduction of glass powder and NBR to the phenolic matrix as well as by the cure conditions given.

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J2-bounding Surface Plasticity Model with Zero Elastic Region (탄성영역이 없는 J2-경계면 소성모델)

  • Shin, Hosung;Oh, Seboong;Kim, Jae-min
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.43 no.4
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    • pp.469-476
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    • 2023
  • Soil plasticity models for cyclic and dynamic loads are essential in non-linear numerical analysis of geotechnical structures. While a single yield surface model shows a linear behavior for cyclic loads, J2-bounding surface plasticity model with zero elastic region can effectively simulate a nonlinearity of the ground response with the same material properties. The radius of the yield surface inside the boundary surface converged to 0 to make the elastic region disappear, and plastic hardening modulus and dilatancy define plastic strain increment. This paper presents the stress-strain incremental equation of the developed model, and derives plastic hardening modulus for the hyperbolic model. The comparative analyses of the triaxial compression test and the shallow foundation under the cyclic load can show stable numerical convergence, consistency with the theoretical solution, and hysteresis behavior. In addition, plastic hardening modulus for the modified hyperbolic function is presented, and a methodology to estimate model variables conforming 1D equivalent linear model is proposed for numerical modeling of the multi-dimensional behavior of the ground.

Liquid Crystal Orientation on LaGaO Thin Films Induced by a Brush Coating Process (브러시 코팅 공정에 의해 유도된 LaGaO 박막의 액정 배향)

  • Byeong-Yun Oh
    • Journal of IKEEE
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    • v.28 no.3
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    • pp.261-270
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    • 2024
  • In this study, a lanthanum gallium oxide (LaGaO) solution was prepared using a sol-gel method. By simply forming a LaGaO thin film through adjusting the curing temperature after applying the solution onto the substrate using a brush coating process, the potential for use as a liquid crystal (LC) alignment film in the LC display industry was validated. Through optical microscope observation, it was confirmed that the LC molecules were uniformly aligned as the curing temperature of the LaGaO thin film increased. It was confirmed that the LaGaO thin film cured at 230℃ had low pretilt angle, and that LaGaO particles were formed in a single direction as observed through an atomic force microscope. Through X-ray photoelectron spectroscopy, it was found that the LaGaO metal oxide thin film was well formed. Finally, it has been confirmed that LaGaO metal oxide has the potential as a novel LC alignment film material, as it exhibits excellent electrical and optical properties, along with high optical transmittance.

Heating Behavior and Adhesion Property of Epoxy Adhesive with Nano and Micro Sized Fe3O4 Particles (Nano 및 Micro 크기의 Fe3O4 분말이 첨가된 열경화성 에폭시 접착제의 유도가열 및 접착 특성)

  • Hwang, Ji-Won;Im, Tae-Gyu;Choi, Seung-Yong;Lee, Nam-Kyu;Shon, Min-Young
    • Composites Research
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    • v.33 no.2
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    • pp.55-60
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    • 2020
  • A study on the heating behavior and adhesion property of structural epoxy adhesive through induction heating have been conducted. An adhesive for induction heating was manufactured through mixing with nano and micro sized Fe3O4. From the results, it was observed that induction heating is less affected by adherend (GFRP) thickness than oven heating. The heating rate of Fe3O4 embedded epoxy adhesive using induction heating much higher than that of oven curing process and it is more appreciable when the contents of Fe3O4 increased. Furthermore, adhesion strength increased with increase of Fe3O4 particle contents.

In Vitro Shoot Multiplication of Albizzia julibrissin Duraz. (자귀나무(Albizzia julibrissin Duraz.)의 기내 대량증식)

  • Ahn, Ji-Young;Kim, Jung-Hee;Kang, Ho-Duck
    • Korean Journal of Plant Resources
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    • v.19 no.4
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    • pp.524-529
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    • 2006
  • In vitro culture system was established to induce multiple shoots of Albizzia julibrissin Duraz. by investigating the effects of cytokinins. Cotyledon, hypocotyl and root explants were cultured on MS media supplemented with either three different plant growth regulators or their combinations. The most effective cytokinin sources were zeatin 2.0 + TDZ 0.5 mg/L in cotyledon, zeatin 1.0 mg/L in hypocotyl, and BA 0.2 + TDZ 0.01 mg/L in root explant for producing shoots (5.67±1.20, 19.50±3.50, and 20.50±2.47, respectively). Also, zeatin treatment was tended to induce more shoots rather than the combinations of other cytokinins. In addition, the root induced in 1/2 MS medium without any plant growth regulators was longer and thicker than treatments of IBA, NAA, IAA and 2.4-D as auxins. Overall, the highest average percent of in vitro shoot formation was 73% from three different types of explants with treatment of zeatin (1.0mg/L).

Dynamic Instability of Strength-Limited Bilinear SDF Systems (강도한계 이선형 단자유도 시스템의 동적 불안정)

  • Han, Sang-Whan;Kim, Jong-Bo;Bae, Mun-Su;Moon, Ki-Hoon
    • Journal of the Earthquake Engineering Society of Korea
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    • v.12 no.5
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    • pp.23-29
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    • 2008
  • This study investigates the dynamic instability of strength-limited bilinear single degree of freedom (SDF) systems under seismic excitation. The strength-limited bilinear hysteretic model best replicates the hysteretic behavior of the steel moment resisting frames. To estimate the dynamic instability of SDF systems, the collapse strength ratio is used, which is the yield-strength reduction factor when collapse occurs. Statistical studies are carried out to estimate median collapse strength ratios and those dispersions of strength-limited bilinear SDF systems with given natural periods, hardening stiffness ratios, post-capping stiffness ratios, ductility and damping ratios ranging from 2 to 20% subjected to 240 earthquake ground motions recorded on stiff soil sites. Equations to calculate median and standard deviation of collapse strength ratios in strength-limited bilinear SDF systems are obtained through nonlinear regression analysis. By using the proposed equations, this study estimated the probabilistic distribution of collapse strength ratios, and compared this with the exact values from which the accuracy of the proposed equations was verified.

Effects of Dielectric Curing Temperature and T/H Treatment on the Interfacial Adhesion Energies of Ti/PBO for Cu RDL Applications of FOWLP (FOWLP Cu 재배선 적용을 위한 절연층 경화 온도 및 고온/고습 처리가 Ti/PBO 계면접착에너지에 미치는 영향)

  • Kirak Son;Gahui Kim;Young-Bae Park
    • Journal of the Microelectronics and Packaging Society
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    • v.30 no.2
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    • pp.52-59
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    • 2023
  • The effects of dielectric curing temperature and temperature/humidity treatment conditions on the interfacial adhesion energies between Ti diffusion barrier/polybenzoxazole (PBO) dielectric layers were systematically investigated for Cu redistribution layer applications of fan-out wafer level package. The initial interfacial adhesion energies were 16.63, 25.95, 16.58 J/m2 for PBO curing temperatures at 175, 200, and 225 ℃, respectively. X-ray photoelectron spectroscopy analysis showed that there exists a good correlation between the interfacial adhesion energy and the C-O peak area fractions at PBO delaminated surfaces. And the interfacial adhesion energies of samples cured at 200 ℃ decreased to 3.99 J/m2 after 500 h at 85 ℃/85 % relative humidity, possibly due to the weak boundary layer formation inside PBO near Ti/PBO interface.

Performance of Fresh and Hardened Ultra High Performance Concrete without Heat Treatment (상온 양생한 초고성능 콘크리트(UHPC)의 경화 전과 후의 성능 관계)

  • Kang, Sung-Hoon;Hong, Sung-Gul
    • Journal of the Korea Concrete Institute
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    • v.26 no.1
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    • pp.23-34
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    • 2014
  • This study investigates the relationship between the performance of fresh and hardened Ultra-High Performance Concrete (UHPC) without heat treatment. The performance of fresh UHPC is determined by the slump flow test related to the fluidity of concrete mixtures, and the air content test. The variables of these tests are the water to binder ratio, superplasticizer dosages and volume fractions of steel fiber. Generally, insufficient fluidity and excessive air contents in concrete mixtures lead to the insufficient packing density related to the performance of harden concrete. The performance of hardened UHPC is determined by the compressive and flexural tensile tests. The results of the fresh UHPC tests show that there is the linear correlation between each variable and the slump flow diameter, and that the slump flow diameter is linearly decreased as the air content ratio increase. Using these results, the formula is developed to predict the fresh performance before mixing UHPC. The results of the hardened UHPC tests show that the hardened performance is not influenced by the air content ratio in the range of 3.2 to 4.2 per cent. However, the flexural tensile strength dominantly influenced by the volume fractions of steel fiber.

Effects of Cheonggukjang Powder Made with Black Foods on Liver Function and Lipid Composition in Streptozotocin-induced Diabetic Rats (블랙푸드로 만든 청국장분말 식이가 Streptozotocin으로 유도된 당뇨 쥐의 간 기능과 지질 조성에 미치는 영향)

  • Park, Hyeon-Sook;Yang, Kyung-Mi
    • Korean journal of food and cookery science
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    • v.29 no.6
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    • pp.699-707
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    • 2013
  • This study was conducted to examine the effects of Cheonggukjang powder made using black foods on liver function and lipid composition in streptozotocin(STZ)-induced diabetic rats. The experimental animals were divided into 5 groups and fed the following for 7 weeks; normal diet(control), STZ+normal diet(Diabetic), STZ+50% soybean Cheonggukjang supplementation(DSC), STZ+44.5% yakkong Cheonggukjang supplementation(DYC), and STZ+supplementation with 50% yakkong black food(black rice, black sesame seeds, and sea tangle) Cheonggukjang(DYCB). The results showed that the body weight gain and food efficiency ratio of the STZ-induced diabetic groups were significantly lower than those of the control group. In the Diabetic group, glutamic oxaloacetic transaminase(GOT) and glutamic pyruvic transaminase(GPT) activities and total bilirubin content in serum were significantly greater than those in the control group. However, supplementation with Cheonggukjang reduced these values. In the Diabetic group, the triglyceride, total cholesterol, and low-density lipoprotein(LDL)-cholesterol contents in the serum and liver tissue, as well as the atherogenic index(AI) and cardiac risk factors(CRF) were significantly higher than the corresponding values in the control group, although the high-density lipoprotein(HDL)-cholesterol and phospholipid contents were significantly lower than those in the control group. However, supplementation with Cheonggukjang normalized the changed lipid composition in the STZ-induced diabetic rats. Further, yakkong Cheonggukjang and black food contaning yakkong Cheonggukjang normalized AI and CRF.