• Title/Summary/Keyword: High temperature properties

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A Study on Adhesive Crosslinked in Low Temperature for High Temperature Aerospace Application (우주항공용 저온 경화 접착제의 고온 물성에 관한 연구)

  • Song, Jung Kun;Woo, Hyun Ryul;Lee, Geum Mi;Choi, Doo Hyun
    • Journal of the Korea Institute of Military Science and Technology
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    • v.22 no.2
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    • pp.215-223
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    • 2019
  • A high temperature adhesive development which is crosslinked in low temperature is necessary for aerospace application because of thermal expansion mismatches of various substrates. For this purpose, we have designed and fabricated several formulations with high temperature epoxy resins, crosslinkers and additives considering various working conditions and high service temperature. As a result, some formulations showed higher adhesive strengths than Hysol EA 9394/C2 which is widely used for aerospace applications. We also have studied and summarized the mechanical properties of the best development adhesive in both room and high temperatures.

Relationship between Creep Characteristic Values and Rupture time in STS304 Stainless Steels (스테인리스강의 크리프 특성치와 파단시간과의 관계)

  • KONG YU-SIK;KIM SEON-JIN;LEE BAE-SUB
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2004.11a
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    • pp.228-233
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    • 2004
  • The characteristics of the probability distribution for mechanical properties, e.g. tensile strength, reduction of area ana elongation, for STS304 stainless steel in elevated temperature were investigated from tensile test performed by constant cross head speea controls with 1mm/min, Recently, in order to clarify the strengthening mechanisms at high temperature, a new scheme to improve high temperature mechanical properties is desired. Therefore, the test ,technique development of high temperature creep behaviors for this material is very important. In this paper, the creep praperties and creep life prediction by Larson-Miller parameter method for STS304 stainless steel to be used for other high temperature components were presented at the elevated temperatures of 600, 650 and $700^{\circ}C$.

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Mechanical Properties of Polypropylene Filaments Drawn on Varying Post Spinning Temperature Gradients

  • Mukhopadhyay, S.;Deopura, B.L.;Alagirusamy, R.
    • Fibers and Polymers
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    • v.7 no.4
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    • pp.432-435
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    • 2006
  • High Modulus and high tenacity polypropylene fibers have been prepared by drawing on a gradient heater. Results show that fiber properties are significantly affected by temperature profiles of final stage drawing on a gradient heater. The gradient drawn filaments showed superior mechanical properties when compared to filaments drawn over a constant temperature heater. Fibers with initial modulus of 16.4 GPa and tenacity of 670 MPa have been manufactured in the process. The nature of the gradient drawing had a significant effect on end properties. The superior mechanical properties are attributed to the high crystal perfection and crystallinity and low void fractions obtained at high draw ratios when drawn over a gradient heater.

The Effect of Temperature on Tensile Properties in Conventionally Cast Ni-based Superalloy CM247LC (다결정 니켈기 초내열 합금 CM247LC의 온도에 따른 인장특성 변화)

  • Choi, Baig-Gyu;Kim, In Soo;Do, Jeonghyeon;Jung, Joong Eun;Seok, Woo-Young;Lee, Yu-Hwa
    • Journal of Korea Foundry Society
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    • v.40 no.4
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    • pp.118-127
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    • 2020
  • Microstructural evolution during a heat treatment and high-temperature tensile properties have been investigated in conventionally cast CM247LC. In as-cast specimens, MC carbides with high amounts of Ta, Ti, Hf, and W were found to exist in the interdendritic regions, and γ' was observed in the form of cubes and octocubes prior to decomposition into cubes. In the heat-treated condition, some portion of eutectic γ-γ' remained, and uniform cubic γ' was observed in both interdendritic regions and dendrite core. Three types of carbides with different stoichiometries and compositions were found at the grain boundaries. MC carbides with high Hf contents were observed in the vicinity of eutectic γ-γ'. The highest tensile strength value was found at 750℃, whereas the greatest ductility appeared at 649℃. The effect of the temperature on the tensile properties was closely related to the dislocation structure. With increase in the test temperature, the density of dislocations inside γ' decreased, whereas that in the γ matrix increased. Stacking faults generated in γ' at 750℃ had a strengthening effect, whereas thermally activated dislocation motion at a high temperature was considered to have the opposite effect.

Geomechanical study of well stability in high-pressure, high-temperature conditions

  • Moradi, Seyyed Shahab Tabatabaee;Nikolaev, Nikolay I.;Chudinova, Inna V.;Martel, Aleksander S.
    • Geomechanics and Engineering
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    • v.16 no.3
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    • pp.331-339
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    • 2018
  • Worldwide growth in hydrocarbon and energy demand is driving the oil and gas companies to drill more wells in complex situations such as areas with high-pressure, high-temperature conditions. As a result, in recent years the number of wells in these conditions have been increased significantly. Wellbore instability is one of the main issues during the drilling operation especially for directional and horizontal wells. Many researchers have studied the wellbore stability in complex situations and developed mathematical models to mitigate the instability problems before drilling operation. In this work, a fully coupled thermoporoelastic model is developed to study the well stability in high-pressure, high-temperature conditions. The results show that the performance of the model is highly dependent on the truly evaluated rock mechanical properties. It is noted that the rock mechanical properties should be evaluated at elevated pressures and temperatures. However, in many works, this is skipped and the mechanical properties, which are evaluated at room conditions, are entered into the model. Therefore, an accurate stability analysis of high-pressure, high-temperature wells is achieved by measuring the rock mechanical properties at elevated pressures and temperatures, as the difference between the model outputs is significant.

Prediction of mechanical properties of limestone concrete after high temperature exposure with artificial neural networks

  • Blumauer, Urska;Hozjan, Tomaz;Trtnik, Gregor
    • Advances in concrete construction
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    • v.10 no.3
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    • pp.247-256
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    • 2020
  • In this paper the possibility of using different regression models to predict the mechanical properties of limestone concrete after exposure to high temperatures, based on the results of non-destructive techniques, that could be easily used in-situ, is discussed. Extensive experimental work was carried out on limestone concrete mixtures, that differed in the water to cement (w/c) ratio, the type of cement and the quantity of superplasticizer added. After standard curing, the specimens were exposed to various high temperature levels, i.e., 200℃, 400℃, 600℃ or 800℃. Before heating, the reference mechanical properties of the concrete were determined at ambient temperature. After the heating process, the specimens were cooled naturally to ambient temperature and tested using non-destructive techniques. Among the mechanical properties of the specimens after heating, known also as the residual mechanical properties, the residual modulus of elasticity, compressive and flexural strengths were determined. The results show that residual modulus of elasticity, compressive and flexural strengths can be reliably predicted using an artificial neural network approach based on ultrasonic pulse velocity, residual surface strength, some mixture parameters and maximal temperature reached in concrete during heating.

Physical Properties of 50MPa and 80MPa Ternary High Strength Concretes before and after Concrete Pumping

  • Lee, Bum-Sik;Kim, Seong-Deok;Jun, Myoung-Hoon;Park, Sung-Sik;Park, Su-Hee;Jung, Sang-Jin
    • Journal of the Korea Institute of Building Construction
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    • v.12 no.4
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    • pp.451-459
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    • 2012
  • At the Korea Land and Housing Corporation(LH), concretes with high design strength of 50 MPa and 80 MPa that are composed only of ordinary Portland cement, blast furnace slag, and fly ash are developed. To determine whether the developed high strength concretes have the same properties when they are produced in batch plant(B/P) condition in the ready mixed concrete plant, and as existing high strength concretes, field tests are performed and material properties are evaluated. To investigate the material properties of the high strength concretes before and after pumping, compressive strength, flowability, air content, hydration temperature, pumping and compactability are evaluated. In field tests, before and after pumping, flowability satisfied the relevant criteria. In terms of air content, while it was slightly decreased after pumping, it satisfied the requirements. Hydration temperature criteria were satisfied, and compactability was excellent as well. The study found that the developed ternary high strength concretes have the same properties as existing high strength concretes. They can also be useful for the construction of high-rise buildings, as they are economical.

Evaluation of Mechanical Properties of Carbon/Epoxy Composites Under In situ Low- and High-Temperature Environments (저온과 고온 환경 하에서 카본/에폭시 복합재의 기계적 물성 평가)

  • Im, JaeMoon;Shin, KwangBok;Hwang, Taekyung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.6
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    • pp.567-573
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    • 2015
  • This paper aims to evaluate the variation in the mechanical properties of carbon/epoxy composites under in situ low- and high-temperature environments. In situ low- and high-temperature environments were simulated with temperature ranging from $-40^{\circ}C$ to $220^{\circ}C$ using an environmental chamber and furnace. The variation in the mechanical properties of the composites was measured for longitudinal and transverse tensile properties, in-plane shear properties and interlaminar shear strength. Under the low temperature of $-40^{\circ}C$, all mechanical properties increased moderately compared to the baseline properties measured at room temperature. The changes in the longitudinal tensile properties decreased moderately with increasing temperature. However, transverse tensile properties, in-plane shear properties and interlaminar shear strength each showed a significant drop due to the glass transition behavior of the matrix after $140^{\circ}C$. Notably, the tensile property value near $100^{\circ}C$ increased compared to baseline property value, which was an unusual occurrence. This behavior was a direct result of post-curing of the epoxy resin due to its exposure to high temperature.

Correlation between the Properties of Superpave Binder and Engineering Properties of Recycled Aged CRM Mixtures (재생 CRM 바인더와 혼합물의 성능 상관성 연구)

  • Kim, Hyun Hwan;Jeong, Kyu Dong;Lee, Moon Sup;Lee, Soon Jae
    • International Journal of Highway Engineering
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    • v.18 no.2
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    • pp.1-9
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    • 2016
  • PURPOSES : The performance properties (indirect tensile strength, rutting resistance, and resilient modulus) of recycled aged CRM mixtures and their correlation with Superpave binder properties (viscosity, high failure temperature, $G^*sin{\delta}$, and stiffness) were investigated. METHODS: A series of Superpave binder tests was performed by using a rotational viscometer, DSR, and BBR to evaluate the performance properties. In addition, the CRM mixes were artificially aged through accelerated aging processes, and their properties were evaluated. The correlation between the properties of recycled aged CRM binders and the engineering properties of recycled aged CRM mixtures was experimentally determined. RESULTS : The rut depth values decreased and the ITS values increased with increasing high failure temperature. In general, the resilient modulus properties seemed to be poorly correlated with the high-temperature values, regardless of the aggregate source. CONCLUSIONS: The recycled aged CRM binders and mixtures can lead to satisfactory performance, and the properties of these binders are strongly correlated with the engineering properties of the mixtures.