• Title/Summary/Keyword: Heat intensity

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Effect of Crosslinking on the PTC Stability Carbon Black Filled HDPE/EEA Copolymer Composite (카본블랙 충전 HDPE/EEA Copolymer 복합재료에 있어서 가교구조가 PTC 특성에 미치는 영향)

  • Lee, Gun-Joo
    • Proceedings of the KIEE Conference
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    • 2001.11a
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    • pp.140-145
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    • 2001
  • In order to apply for silane crosslinking process to PTC products, especially. self-regulating heater, silane crosslinked samples were compared with radiation crosslinked sample in terms of PTC characteristic and PTC stability. Silane crosslinked samples have lower PTC intensity than radiation crosslinked sample. It can be explained that multiple networks of silane crosslink restrict the movement of molecules in the composite as the sample is heating. As a result of heat cycles at $140^{\circ}C$, the changes of volume resistivity and PTC intensity for radiation crosslinked sample were higher than those of silane crosslinked samples. Whereas, in the case of heat cycles at $85^{\circ}C$, which is limiting temperature for self-regulating heater, both silane and radiation crosslinked samples show stable results without pronounce changes of resistivity up to five cycles.

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A study on stress corrosion cracking of weld zone in 304-stainless steel (304 스테인레스鋼 熔接部의 응력부식구열에 관한 硏究)

  • 김경일;강인찬
    • Journal of Welding and Joining
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    • v.5 no.2
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    • pp.35-43
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    • 1987
  • The effect of post weld heat treatment (P.W.H.T) on the propagation rate of stress corrosion cracking(S.C.C) and threshold stress intensity factor ($K_{IC}.c.c$) for stress corrosion cracking of 304 stainless steel has been investigated in boiling 45% $MgCl_2$ solutions with W.O.L specimens. Specimens were precracked by turning a pair of Cr-Mo steel bolts into a machined slot at the end of the specimen. The fracture surface was examined fractographically by Scanning Electron Microscope(S.E.M.)

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The Dependency of CH* Chemiluminescence of a Laminar Premixed Flame on Fuel Types (연료에 따른 층류 예혼합화염의 CH* Chemiluminescence 신호특성 변화)

  • Lee, Won-Nam;Kang, Suk-Min
    • Journal of the Korean Society of Combustion
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    • v.13 no.2
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    • pp.14-22
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    • 2008
  • The CH* chemiluminescence of premixed flames and their dependency on fuel types has been experimentally investigated on laminar methane and propane premixed flames. The measured chemiluminescence intensities are observed linearly proportional to the fuel flow rate, which could be interpreted as the CH* chemiluminescence signal is linearly proportional to the heat release rate under fuel lean conditions. The effect of equivalence ratio could be expressed by an exponential function as ${I_{CH*}}^{\propto}\;a_1\;{\exp}(b_1{\Phi})$, where $a_1\;=\;0.00054$ and $b_1\;=\;4.60$ for methane and $a_1\;=\;0.0056$ and $b_1\;=\;5.02$ for propane. Oscillating flames showed the temporal fluctuation of chemiluminescence intensity: however, the time averaged values are virtually identical to those of quiescent flames under the same fuel flow rate and equivalence ratio conditions. This observation suggests that there is no significant flame stretch effect on chemiluminescence intensity, in average values.

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Strength Development of Mock-up Concrete Structure subjected to Extremely Low Temperature Condition Due to Curing Methods (극저온 조건에서의 양생방법 변화에 따른 실구조체 콘크리트의 강도발현 특성)

  • Jung, Eun-Bong;Jung, Sang-Hyeon;Ahn, Sang-Ku;Ko, Gyeong-Taek;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2012.11a
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    • pp.47-49
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    • 2012
  • Under this study, the characteristics of concrete intensity condition following the curing method under the extremely low temperature environment have been contemplated, and as a result, in the event of insulation + heat cable curing, the intensity and accumulated temperature accomplishment period is required for two times of requiring initial frost damage prevention than the case of heating + heat insulation curing method due to the insufficient calories supplied in general.

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Design of Shrinkage Margin for Thin Panel Welded Structure during Manufacturing Process

  • Lee D. J.;Shin S. B.
    • International Journal of Korean Welding Society
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    • v.5 no.1
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    • pp.44-52
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    • 2005
  • The purpose of this study is to establish a design tool for the shrinkage margin of a deckhouse caused by welding and flame straightening. In order to do it, the effects of heat intensity and internal/external restraint condition on the shrinkage of the simple weldments were investigated, in order to identity the principal factors controlling shrinkage caused by welding process and flame straightening. Based on the results, predictive equations for longitudinal and transverse shrinkage at the welded structure were formulated as the function of heat intensity and in-plane rigidity. These equations were verified by comparing predicted results with the measured results at a panel structure of deckhouse.

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Source Identification and Reduction of Noise for the Outdoor Unit of Room Air Conditioner (에어컨 실외기의 소음원 규명 및 소음저감)

  • 서상호;임금식;이내영;진심원
    • Journal of KSNVE
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    • v.8 no.6
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    • pp.1043-1052
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    • 1998
  • The noise sources in the outdoor unit of RAC are identified by the sound intensity method. The main noise sources are compressor noise and fluid noise which is caused by the fan. heat exchanger and shroud. First. the fluid noise is reduced through the design of new fan and shroud. reduction of the system resistance by rearrangement of heat exchanger. and optimization of the complex parameter between the fan and shroud. Next, in order to reduce the compressor noise, the new shape of compressor mount and sound-proof material was applied. As a result, the overall noise was reduced by 4∼5dB (A).

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Effect of Nitriding on Fatigue Crack Initiation and Growth Rate in Ni-Cr-Mo Steel (SNCM강의 피로균열의 발생 및 전파속도에 미치는 질화처리의 영향)

  • Kim, Min-Gun;Lim, Bok-Kyu
    • Journal of the Korean Society for Heat Treatment
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    • v.16 no.6
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    • pp.315-319
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    • 2003
  • Effect of nitriding on fatigue crack initiation and growth rate has been studied in Ni-Cr-Mo steel. Specimens were nitrided at $860^{\circ}C$ for 15 hr. The fatigue limit of nitrided specimens were superior to those ofannea1ed($860^{\circ}C$, 15 hr) specimens. Based on detailed observations of slip band and micro crack initiation, it is concluded that the excellent fatigue limit of nitrided specimens is attributed to improved slip initiation resistance by nitriding. The characteristic of fatigue crack growth rate of nitrided specimens was investigated by comparing with those of annealed specimens. It was found that the crack growth rate was markedly decreased and the threshold stress intensity factor range was improved by nitriding. It is concluded that the excellent fatigue limit of nitrided specimens is also attributed to improved fatigue crack growth rate and threshold stress intensity factor range by nitriding.

Thermal Stresses in a Laminated Fiber-Reinforced Composite Containing an Interlaminar Crack Under a Uniform Heat Flow (층간균열이 존재하는 균일 열유동하의 섬유강화 적층복합재료의 열응력해석)

  • 최형집;오준성;이강용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.4
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    • pp.887-902
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    • 1994
  • Within the framework of anisotropic thermoelasticity, the problem of an interlaminar crack in a laminated fiber-reinforced composite subjected to a uniform heat flow is investigated. Under a state of generalized plane deformation, dissimilar anisotropic half-spaces with different fiber orientations are considered to be bound together by a matrix interlayer containing the crack. The interlayer models the matrix-rich interlaminar region of the fibrous composite laminate. Based on the flexibility/stiffness matrix approach, formulation of the current crack problem results in having to solve two sets of singular integral equations for temperature and thermal stress analyses. Numerical results are obtained, illustrating the parametric effects of laminate stacking sequence, relative crack size, crack location, crack surface partial insulation, and fiber volume fraction on the values of mixed mode thermal stress intensity factors.

Pressure-Temperature Limit Curve of Reactor Vessel by ASME Code Section III and Section XI

  • M.J. Jhung;Kim, S.H.;Lee, T.J.
    • Nuclear Engineering and Technology
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    • v.33 no.5
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    • pp.498-513
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    • 2001
  • Performed here is a comparative assessment study for the generation of the pressure- temperature (P/T) limit curve of the reactor vessel. Using the cooling or heating rate and vessel material properties, the stress distribution is obtained to calculate stress intensity factors, which are compared with the material fracture toughness to determine the relations between operating pressure and temperature during cool-down and heat-up. P/T limit curves are generated with respect to crack direction, clad thickness, toughness curve, cooling or heating rate and neutron fluence, and their results are compared.

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Evaluation of Residual Stresses of Hardened Surface by Magnetoelastic Method (Magnetoelastic Method를 이용한 표면 경화층의 잔류응력 평가)

  • Nam, O.B.;Lee, I.W.;Kim, S.W.;Kim, M.I.
    • Journal of the Korean Society for Heat Treatment
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    • v.5 no.3
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    • pp.157-164
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    • 1992
  • Barkhausen noise (BN) is created by the abrupt changes in the magnetization of materials under applied AC magnetizing field. These changes are known to be sensitive to residual and applied stresses. In this study, BN theory was reviewed and it was examined how BN intensity was affected by simultaneous stress, hardness and microstructural changes. Also, magnetoelastic effect was used to evaluate residual stresses through carrying out the cantilever beam test. An increase in BN intensity was observed when applied and residual stress changes from compression into tension. Microstructural softening by tempering also increased the amount of BN. Therefore, the quantitative evaluation of residual stress and microstructural changes will be possible, provided BN method is more studied about various materials through comparing with different stress measuring techniques.

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