• Title, Summary, Keyword: Thermal Stress

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Prediction of thermal stress in concrete structures with various restraints using thermal stress device

  • Cha, Sang Lyul;Lee, Yun;An, Gyeong Hee;Kim, Jin Keun
    • Computers and Concrete
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    • v.17 no.2
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    • pp.173-188
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    • 2016
  • Generally, thermal stress induced by hydration heat causes cracking in mass concrete structures, requiring a thorough control during the construction. The prediction of the thermal stress is currently undertaken by means of numerical analysis despite its lack of reliability due to the properties of concrete varying over time. In this paper, a method for the prediction of thermal stress in concrete structures by adjusting thermal stress measured by a thermal stress device according to the degree of restraint is proposed to improve the prediction accuracy. The ratio of stress in concrete structures to stress under complete restraint is used as the degree of restraint. To consider the history of the degree of restraint, incremental stress is predicted by comparing the degree of restraint and the incremental stress obtained by the thermal stress device. Furthermore, the thermal stresses of wall and foundation predicted by the proposed method are compared to those obtained by numerical analysis. The thermal stresses obtained by the proposed method are similar to those obtained by the analysis for structures with internally as well as externally strong restraint. It is therefore concluded that the prediction of thermal stress for concrete structures with various boundary conditions using the proposed method is suggested to be accurate.

Thermal Fatigue Life Prediction of Alumina by Finite Difference Model (유한 차분 모델을 이용한 알루미나의 열피로 수명 예측)

  • 이홍림;한봉석
    • Journal of the Korean Ceramic Society
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    • v.30 no.3
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    • pp.229-235
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    • 1993
  • Thermal history and thermal stress of alumina specimen, which occured from thermal shock process, were calculated by finite difference method. Stress intensity factor and crack growth in cyclic thermal fatigue were calculated from single thermal shock temperature history and thermal stress. Cyclic thermal life were estimated by bending strength after cyclic thermal shock under critical thermal shock temperature. Calculated stress intensity factor was compared with real experimental thermal fatigue life of specimen. Fatigue life until critical stress intensity factor and real experimental result were comparable.

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Residual Stress Measurement of Sand Casting by ESPI Device and Thermal Stress Analysis (ESPI 장비를 활용한 사형 주조품의 잔류응력 측정 및 주조 열응력 해석)

  • Kwak, Si-Young;Nam, Jeong-Ho
    • Journal of Korea Foundry Society
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    • v.40 no.1
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    • pp.1-6
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    • 2020
  • Many studies involving a thermal stress analysis using computational methods have been conducted, though there have been relatively few experimental attempts to investigate thermal stress phenomena. Casting products undergo thermal stress variations during the casting process as the temperature drops from the melting temperature to room temperature, with gradient cooling also occurring from the surface to the core. It is difficult to examine thermal stress states continuously during the casting process. Therefore, only the final states of thermal stress and deformations can be detemined. In this study, specimens sensitive to thermal stress, were made by a casting process. After which the residual stress levels in the specimens were measured by a hole drilling method with Electron Speckle-Interferometry technique. Subsequently, we examined the thermal stresses in terms of deformation during the casting process by means of a numerical analysis. Finally, we compared the experimental and numerical analysis results. It was found that the numerical thermal stress analysis is an effective means of understanding the stress generation mechanism in casting products during the casting process.

Thermal Stress Intensity Factors for Partially Insulated Interface Crack under Uniform Heat Flow (부분 열유동이 있는 접합 경계면균열의 열응력세기계수 결정)

  • 이강용;박상준
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.7
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    • pp.1705-1712
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    • 1994
  • Hilbert problems are derived to evaluate thermal stress intensity factors for a partially insulated crack subjected to vertically uniform heat flow in infinite bonded dissimilar materials. In case of fully insulated crack surface, the present solutions of thermal stress intensity factors are reduced into the same as the previous results. For the homogeneous material, mode II thermal stress intensity factor only exists. However, in the bonded dissimilar materials, both mode I and II thermal stress intensity factors are obtained. Specially, in this case, mode II thermal stress intensity factor is dominent. Also, thermal stress intensity factors are strongly influenced by the material properties. Thermal stress intensity factors decrease when the degree of insulation decreases.

Thermal Stress at the Junction of Skirt to Head in Hot Pressure Vessel (고온 수직형 압력용기 Skirt 부의 열응력에 관한 연구)

  • 한명수;한종만;조용관
    • Journal of Welding and Joining
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    • v.16 no.2
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    • pp.111-121
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    • 1998
  • It is well recognized that a excessive temperature gradient from the junction of head to skirt in axial direction in a hot pressure vessel can cause unpredicted high thermal stress at the junction and/or in axial direction of a skirt. this thermal stress resulting from axial thermal gradient may be a major cause of unsoundness of structural integrity. In case of cyclic operation of hot pressure vessels, the thermal stress becomes one of the primary design consideration because of the possibility of fracture as a result of cyclic thermal fatigue and progressively incremental plastic deformation. To perform thermal stress analysis of the junction and cylindrical skirt of a vessel, or, at least, to inspect quantitatively the magnitude and effect of thermal stress, the temperature profile of the vessel and skirt must be known. This paper demonstrated the temperature distribution and thermal stress analysis for the junction of skirt to head using F.E. analysis. Effect of air pocket in crotch space was quantitatively investigated to minimize the temperature gradient causing the thermal stress in axial direction. Effect of the skirt height on thermal stresses was also studied. Analysis results were compared with theoretical formulas to verify th applicability to the strength calculation in design field.

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Thermal Stress Analysis of STS VOD Ladle according to the reinforcement of back filler (Back Filler의 보강에 따른 STS VOD 래들의 열응력 해석)

  • Lee, S.W.;Ham, K.C.;Bae, S.I.;Song, J.I.
    • Proceedings of the KSME Conference
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    • pp.310-315
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    • 2000
  • We analyzed thermal stress of the STS VOD ladle by the variation of material property of refractory, and determined the location of back filler using FE analysis. Thermal distribution of refractory of ladle between hot face and back face were decreased by the increasing the thermal conductivity, and thermal stress of refractory were decreased about 2 to 4 times with the decreasing the young's modulus coefficients. Back filler, which is constructed to absorb the thermal expansion of dolomite refractory, has relatively low thermal conductivity. Inner side of refractory of ladle maintained high temperature, but temperature of outer side of ladle decreased low. Consequently, inner expansion and outer contraction were appeared. and thermal stress were increased, so thermal stress by the construction of back filler were increased.

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Environmental stress-related gene expression and blood physiological responses in olive flounder (Paralichthys olivaceus) exposed to osmotic and thermal stress

  • Choi, Cheol-Young
    • Animal cells and systems
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    • v.14 no.1
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    • pp.17-23
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    • 2010
  • We isolated warm temperature acclimation-related protein 65-kDa (Wap65) cDNA from the liver of olive flounder and investigated the mRNA expression of Wap65 and HSP70 in olive flounder exposed to osmotic (17.5, 8.75, and 4 psu) and thermal stress (25 and $30^{\circ}C$). The mRNA expression of Wap65 and HSP70 was increased by thermal stress. The mRNA expression of HSP70 was also increased by osmotic stress, whereas no significant change in Wap65 expression was detected. These results indicate that Wap65 mRNA expression occurs specifically in response to increases in water temperature, but not in response to osmotic stress. Plasma cortisol levels were also increased by osmotic and thermal stress. We also utilized the stress hormone cortisol to examine whether Wap65 expression is thermal-stress-specific. Cortisol treatment increased HSP70 mRNA expression in vitro, but had no significant effect on Wap65 mRNA expression. Thus, thermal stress, but not osmotic stress, induces Wap65 expression.

An Experimental Study on the Measurement of Temperature and Thermal Stress of Wall Type Mass Concrete Structure (벽체형 매스콘크리트구조물의 온도 및 온도응력측정에 관한 실험적 연구)

  • 강석화;이용호;정한중;박칠림
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.173-177
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    • 1995
  • Thermal cracks ard occured when thermal stress due to the hydration of cement exceeds the tensile strength of concrete. Since cracking causes poor durability of concrete, the effect of thermal cracking should be included for the desing and construction of massive concrete structures. In this study, an experiments are performed for the investigation of time dependent temperature and thermal stress of massive concrete structure at early ages. In order to measure temperatures and thermal stresses, concrete stress meter, embedded strain meter, non-stress meter, and thermocouples are used. Based on the analyses of measured thermal stress data, measured values by concrete stress meter are more reliable than those by embedded strain meter and non-stress meter, And measured values by concrete stress meter are compared with the calculated values by FEM program developed by DICT (DWTS2D). Calculated values by DWTS2D show good agreement with measured values.

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A Study on Thermal Analysis of Motorcycle Brake Disk (모터싸이클 브레이크 디스크의 열 해석에 관한 연구)

  • Ryu, Mi-Ra;Kim, Young-Hee;Byon, Sang-Min;Park, Heung-Sik
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.8 no.4
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    • pp.34-40
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    • 2009
  • The effect of frictional factors on thermal stress and deformation volume of motorcycle brake disk was studied by using a disk-on-pad type friction tester. It has an effect on the frictional factor such as applied load, sliding speed, sliding distance and number of ventilated disk hole. However, it is difficult to know the mutual relation of these factors. In this study, thermal stress and deformation volume by using design of experiment with 4 elements were investigated for thermal analysis with regression analysis. Thermal stress and thermal deformation are obtained by the application of temperature from mechanical test. From this study, the result showed that the motorcycle brake disk with ventilated hole 3 had the most excellent thermal stress and deformation volume. The regression equation had a trust rate of 95% for the prediction of thermal stress and deformation volume of motorcycle brake disk was composed.

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The Study on Relationship Between Thermal Stress Properties and Thermal Shrinkage of PET Filament Yarns (PET 필라멘트사의 열응력특성과 열수축율과의 상관성연구)

  • 김영진;김승진;김태훈;김경렬;박인동
    • Textile Coloration and Finishing
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    • v.10 no.2
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    • pp.45-54
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    • 1998
  • This study surveys relation between thermal shrinkage and thermal stress properties after process simulation of heat treatment with various PET filament yarns. For this purpose, 12 kinds of regular yarns and POY, 6 kinds of DTY and 5 kinds of composite yarns were experimented for investigating step thermal shrinkage, total thermal shrinkage and total thermal stress and maximum thermal stress temperature. Thermal stress and shrinkage of the various specimens treated with wet and dry heats were analysed and discussed with the conditions of heat treatment. finally, relationship between thermal stress and shrinkage of the various PET filaments such as regular yarns, POY, DTY and composite yarns were investigated with the PET filament characteristics.

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