• Title/Summary/Keyword: Thermal stresses

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A study on the bonding properties of YBCO coated conductors with stabilizer tape (안정화 선재의 YBCO 초전도 접합 특성)

  • Kim Tae-Hyung;Oh Sang-Soo;Ha Dong-Woo;Kim Ho-Sup;Ko Rock-Kil;Shin Hyung-Seop;Park Kyung-Chae
    • Progress in Superconductivity and Cryogenics
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    • v.8 no.3
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    • pp.23-26
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    • 2006
  • For mechanical and electrical stability and environment protection. Cu and stainless steel stabilizers are laminated to a Ag layer to produce a composite neutral-axis(N-A) architecture in which the YBCO layer is centered between the oxide buffered metallic substrate and stabilizer strip lamination. This architecture allows the wire to meet operational requirements including stresses at cryogenic temperature. winding tensions as well as mechanical bending requirements including thermal and electrical stability under fault current conditions. We have experimentally studied mechanical properties of the laminated stainless steel and Cu stabilizers on YBCO coated conductors. We have laminated YBCO coated conductors by continuous dipping soldering process. We have investigated lamination interface between solder and stabilizer of the YBCO coated conductor. We evaluated bonding properties. tensile / shear bonding strength. and peeling strength laminated YBCO coated conductors.

Thermo-Mechanical Analysis of Though-silicon-via in 3D Packaging (Though-silicon-via를 사용한 3차원 적층 반도체 패키징에서의 열응력에 관한 연구)

  • Hwang, Sung-Hwan;Kim, Byoung-Joon;Jung, Sung-Yup;Lee, Ho-Young;Joo, Young-Chang
    • Journal of the Microelectronics and Packaging Society
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    • v.17 no.1
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    • pp.69-73
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    • 2010
  • Finite-element analyses were conducted to investigate the thermal stress in 3-dimensional stacked wafers package containing through-silicon-via (TSV), which is being widely used for 3-Dimensional integration. With finite element method (FEM), thermal stress was analyzed with the variation of TSV diameter, bonding diameter, pitch and TSV height. It was revealed that the maximum von Mises stresses occurred at the edge of top interface between Cu TSV and Si and the Si to Si bonding site. As TSV diameter increased, the von Mises stress at the edge of TSV increased. As bonding diameter increased, the von Mises stress at Si to Si bonding site increased. As pitch increased, the von Mises stress at Si to Si bonding site increased. The TSV height did not affect the von Mises stress. Therefore, it is expected that smaller Cu TSV diameter and pitch will ensure mechanical reliability because of the smaller chance of plastic deformation and crack initiation.

A Study on the Torsional Vibration Characteristics of Super Large Two Stroke Low Speed Diesel Engines with Tuning Damper (튜닝댐퍼를 갖는 초대형 저속 2행정 디젤엔진의 비틀림진동 특성에 관한 연구)

  • Lee, Don-Chool;Barro, Ronald D.
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.1
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    • pp.64-75
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    • 2009
  • The shipbuilder's requirement for a higher power output rating has led to the development of a super large two stroke low speed diesel engines. Usually a large-sized bore engine ranging from $8{\sim}14$ cylinders, this engine group is capable of delivering power output of more than 100,000 bhp at maximum continuous rating(mcr). Other positive aspects of this engine type include higher thermal efficiency, reliability, durability and mobility. This plays a vital role in meeting the propulsion requirement of vessels, specifically for large container ships, of which speed is a primary concern to become more competitive. Consequently, this also resulted in the modification of engine parameters and new component designs to meet the consequential higher mean effective pressure and higher maximum combustion pressure. Even though the fundamental excitation mechanisms unchanged, torsional vibration stresses in the propulsion shafting are subsequently perceived to be higher. As such, one important viewpoint in the initial engine design is the resulting vibration characteristic expected to prevail on the propulsion shafting system(PSS). This paper investigated the torsional vibration characteristics of these super large engines. For the two node torsional vibration with a nodal point on the crankshaft, a tuning damper is necessary to reduce the torsional stresses on the crankshaft. Hence, the tuning torsional vibration damper design and compatibility to the shafting system was similarly reviewed and analyzed.

A Study on the Stress Measurement in a Plastic Product using Chemical Cracking Method (케미칼 크랙킹 방법을 이용한 플라스틱 제품의 응력측정에 관한 연구)

  • Won, S.T.;Kim, T.B.;Lee, S.;Won, J.M.;Cha, K.H.;Lyu, M.Y.
    • Elastomers and Composites
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    • v.47 no.4
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    • pp.336-340
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    • 2012
  • Residual stress in the injection molded part is originated from thermal shrinkage and shear stress during injection molding process. There are many measurement methods of residual stress in the plastic part. Residual stress in opaque products can be measured by chemical cracking test. This method enables the solvent and specimen to react and to cause cracks. Cracks developed according to the level of residual stress. Thus the stresses in plastic part can be quantitatively measured by counting the number of cracks or measuring the size of cracks. Relationship between stress and number of cracks in a plastic specimen has been investigated in this study. Bergen jig was used to give a strain in the specimens those were molded using PC/PBT and PC/ABS. Solvent for the chemical cracking test was prepared using tetrahydrofuran and methyl alcol with the ratio of 1 to 3. Stresses in the specimen can be calculated by strains those were imposed by Bergen jig. Cracks were developed for stress higher than certain level. The number of cracks increased by second order function for stress.

Geomechanical Stability of Underground Lined Rock Caverns (LRC) for Compressed Air Energy Storage (CAES) using Coupled Thermal-Hydraulic-Mechanical Analysis (열-수리-역학적 연계해석을 이용한 복공식 지하 압축공기에너지 저장공동의 역학적 안정성 평가)

  • Kim, Hyung-Mok;Rutqvist, Jonny;Ryu, Dong-Woo;Synn, Joong-Ho;Song, Won-Kyong
    • Tunnel and Underground Space
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    • v.21 no.5
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    • pp.394-405
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    • 2011
  • In this paper, we applied coupled non-isothermal, multiphase fluid flow and geomechanical numerical modeling using TOUGH-FLAC coupled analysis to study the complex thermodynamic and geomechanical performance of underground lined rock caverns (LRC) for compressed air energy storage (CAES). Mechanical stress in concrete linings as well as pressure and temperature within a storage cavern were examined during initial and long-term operation of the storage cavern for CAES. Our geomechanical analysis showed that effective stresses could decrease due to air penetration pressure, and tangential tensile stress could develop in the linings as a result of the air pressure exerted on the inner surface of the lining, which would result in tensile fracturing. According to the simulation in which the tensile tangential stresses resulted in radial cracks, increment of linings' permeability and air leakage though the linings, tensile fracturing occurred at the top and at the side wall of the cavern, and the permeability could increase to $5.0{\times}10^{-13}m^2$ from initially prescribed $10{\times}10^{-20}m^2$. However, this air leakage was minor (about 0.02% of the daily air injection rate) and did not significantly impact the overall storage pressure that was kept constant thanks to sufficiently air tight surrounding rocks, which supports the validity of the concrete-lined underground caverns for CAES.

Tracking/Erosion Resistance Analysis of Nano-Al(OH)3 Filled Silicone Rubber Insulating Materials for High Voltage DC Applications

  • Kannan, P.;Sivakumar, M.;Mekala, K.;Chandrasekar, S.
    • Journal of Electrical Engineering and Technology
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    • v.10 no.1
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    • pp.355-363
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    • 2015
  • HVDC technology has become popular as an economic mode of bulk power transmission over very long distances. Polymeric insulators in HVDC power transmission lines are affected by surface tracking and erosion problems due to contamination deposit, which pose a greater challenge in maintaining the reliability of the HVDC system. In addition, polymeric insulators are also naturally affected by aging due to various environmental stresses, which in turn accelerates the surface tracking and erosion problems. Research works towards the improvement of tracking and erosion resistance of polymeric insulators by adding nano-sized fillers in the base material are being carried out worldwide. However, surface tracking and erosion performance of nano-filled aged polymeric insulators for HVDC applications are not well reported. Hence, in the present work, tracking and erosion resistance of the nano $Al(OH)_3$ filled silicone rubber insulation material has been evaluated under DC voltages at different filler concentrations and aged conditions, as per IEC 60587 test procedures. Leakage current and contact angle measurements were carried out to understand the surface hydrophobicity. Moving average technique was used to analyze the trend followed by leakage current. Water aged specimen shows less tracking resistance when compared with thermal aged specimen. It is observed that nano-filler concentration of 5% is even sufficient to get better tracking/erosion resistance under DC voltages.

Determination and Verification of Flow Stress of Low-alloy Steel Using Cutting Test (절삭실험을 이용한 저합금강의 유동응력 결정 및 검증)

  • Ahn, Kwang-Woo;Kim, Dong-Hoo;Kim, Tae-Ho;Jeon, Eon-Chan
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.13 no.5
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    • pp.50-56
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    • 2014
  • A technique based on the finite element method (FEM) is used in the simulation of metal cutting process. This offers the advantages of the prediction of the cutting force, the stresses, the temperature, the tool wear, and optimization of the cutting condition, the tool shape and the residual stress of the surface. However, the accuracy and reliability of prediction depend on the flow stress of the workpiece. There are various models which describe the relationship between the flow stress and the strain. The Johnson-Cook model is a well-known material model capable of doing this. Low-alloy steel is developed for a dry storage container for used nuclear fuel. Related to this, a process analysis of the plastic machining capability is necessary. For a plastic processing analysis of machining or forging, there are five parameters that must be input into the Johnson-Cook model in this paper. These are (1) the determination of the strain-hardening modulus and the strain hardening exponent through a room-temperature tensile test, (2) the determination of the thermal softening exponent through a high-temperature tensile test, (3) the determination of the cutting forces through an orthogonal cutting test at various cutting speeds, (4) the determination of the strain-rate hardening modulus comparing the orthogonal cutting test results with FEM results. (5) Finally, to validate the Johnson-Cook material parameters, a comparison of the room-temperature tensile test result with a quasi-static simulation using LS-Dyna is necessary.

The Characteristic of Residual Stress and Fracture Toughness on The Welded Joint of HT50 by Laser Welding (50kg급 고장력강 레이저용접부의 용접잔류응력 및 파괴인성 특성)

  • Ro, Chan-Seung;Bang, Han-Sur;Ko, Min-Sung;Kim, Sung-Ju;Kim, Ha-Sig
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2003.10a
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    • pp.93-96
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    • 2003
  • Laser beam welding process is a relatively new process in comparison with arc welding process, but it is expected to apply widely because of the many advantages, and research and development of that process is being progressed actively for the practical use. the application of this welding process has been restricted due to the high initial investment and the need of precise processing against the material, but cost reduction and thick plate welding in high speed have become practial by recent technological development, and this welding process to not only small parts in automobile, machinery and physicochemical field, but also a large structure and pipe line are being applied. In order to utilize this welding process appropriately to a steel structure, the properties of welding residual stresses and fracture toughness in welded joints are to be investigated for relibilty. On this study, after performing the finite element analysis, thermal and residual stress properties have been examined to the general structural steel (HT50) by laser beam welding. Besides, the property of fracture toughness has been investigated by the Charpy impact test and 3-points bending CTOD test carried out in the range of temperature between $-60^{\circ}C$ and $20^{\circ}C$. From the research results it is revealed that the maximum residual stress appears in the center of plate thickness and the fracture toughness is influenced by strength mis-match.

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Unsteady Thermoelasic Deformation and Stress Analysis of a FGM Rectangular Plate (경사기능재료 사각 판의 비정상 열 탄생변형과 응력해석)

  • Kim, Kui-Seob
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.8
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    • pp.91-100
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    • 2004
  • A Green's function approach is adopted for analyzing the thermoelastic deformations and stresses of a plate made of functionally graded materials(FGMs). The solution to the 3-dimensional unsteady temperature is obtained by using the laminate theory. The fundamental equations for thermoelastic problems are derived in terms of out-plane deformation and in-plane force, separately. The thermoelastic deformation and the stress distributions due to the bending and in-plane forces are analyzed by using a Green's function based on the Galerkin method. The eigenfunctions of the Galerkin Green's function for the thermoelastic deformation and the stress distributions are approximated in terms of a series of admissible functions that satisfy the homogeneous boundary conditions of the rectangular plate. Numerical analysis for a simply supported plate is carried out and effects of material properties on unsteady thermoclastic behaviors are discussed.

Lifespan Extension Property of Quercetin-3-O-${\beta}$-D-glucopyranoside-7-O-${\alpha}$-L-rhamnopyranoside from Curcuma longa L. In Caenorhabditis elegans (강황지하부 부산물에서 분리한 Quercetin-3-O-${\beta}$-D-glucopyranoside-7-O-${\alpha}$-L-rhamnopyranoside가 선충의 수명연장에 미치는 영향)

  • Ahn, Dalrae;Lee, Eun Byeol;Kim, Ban Ji;Lee, So Yeon;Ahn, Min-Sil;Eun, Jae Soon;Shin, Tae-Yong;Kim, Dae Keun
    • Korean Journal of Pharmacognosy
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    • v.45 no.4
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    • pp.275-281
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    • 2014
  • After harvesting the medicinal parts of Curcuma longa, the remaining underground parts were discarded. From the remaining underground parts of Curcuma longa quercetin-3-O-${\beta}$-D-glucopyranoside-7-O-${\alpha}$-L-rhamnopyranoside (Q37) was isolated. The antioxidant activities in vitro and lifespan-extension effect of Q37 were elucidated using the Caenorhabditis elegans. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging effect of Q37 showed similar potent activities in comparison with vitamin C. Q37 also showed potent superoxide quenching activities as measured by the riboflavin- and xanthine-originated superoxide quenching activity tests. Q37 prolonged lifespan of worms under normal culture condition. In terms of protective effect of Q37 on the stress conditions such as thermal and oxidative stresses, Q37-treated worms exhibited enhanced survival rate, as compared to control worms. To know the possible mechanism of Q37-mediated increased lifespan and stress resistance of worms, we examined the activities of Q37on superoxide dismutase (SOD), and invested intracellular reactive oxygen species (ROS) levels. The results revealed that Q37 was able to elevate SOD activity of worms and reduce intracellular ROS accumulation in a dose-dependent manner.