• Title/Summary/Keyword: Thermal Fatigue Test

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Evaluation of Effect on Thermal Fatigue Life Considering TGO Growth (TGO 성장이 열피로 수명에 미치는 영향 평가)

  • Song, Hyunwoo;Lee, Jeong-Min;Kim, Yongseok;Oh, Chang-Seo;Han, Kyu Chul;Lee, Young-Ze;Koo, Jae-Mean;Seok, Chang-Sung
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.12
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    • pp.1155-1159
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    • 2014
  • Thermal barrier coating (TBC) which is used to protect the substrate of gas turbine is exposed to high temperature environment. Because of high temperature environment, thermally grown oxide (TGO) is grown at the interface of thermal barrier coating in operation of gas turbine. The growth of TGO critically affects to durability of TBC, so the evaluation about durability of TBC with TGOs of various thickness is needed. In this research, TGO was inserted by aging of TBC specimen to evaluate the effect of the TGO growth. Then thickness of TGO was defined by microstructure analysis, and thermal fatigue test was performed with these aging specimens. Finally, the relation between thermal fatigue life and the TGO growth according to aging time was obtained.

The Evaluation of Mechanical Properties and Fatigue Life for Domestic 304 Stainless Steel Used as Membrane Material in LNG Storage Tank (LNG저장탱크의 멤브레인용 국산 304 스테인리스강의 기계적성질 및 피로수명 평가)

  • Kim, Hyeong-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.10
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    • pp.1644-1650
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    • 2001
  • Mechanical properties of domestic 374 stainless steel have been evaluated fur membrane material used in LNG storage tank. LNG tank is operated around -162$^{\circ}C$. The temperature of membrane depends on LNG level. Accordingly, the membrane material is deteriorated by variation of liquid pressure and temperature. Tensile test and fatigue life test were performed at room temperature and -l62$^{\circ}C$ per code requirements. Especially the biaxial fatigue life test was conducted with shaped membrane sheet at a thermal strain of $\Delta$T=190$^{\circ}C$ The test results obtained with the domestic 304 stainless steel showed better properties compared to the values required by code.

Thermal Barrier Coating Durability Testing Trends for Thrust Chamber of Liquid-propellant Rocket Engine (액체로켓엔진 연소기 열차폐코팅 내구성 시험 기술동향)

  • Lee, Keum-Oh;Ryu, Chul-Sung;Lim, Byoung-Jik;Choi, Hwan-Seok
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.1
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    • pp.103-115
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    • 2013
  • Durability testing method trends of the thermal barrier coating(TBC) for the combustion chamber of the liquid-propellant rocket engine have been investigated. Many types of the durability testing method such as the mechanical tests to measure surface cohesion force, the thermal fatigue tests with laser, furnace, burner or plasma, the small scale combustion tests using injectors, and the thermo-mechanical fatigue tests were observed. The TBC with sufficient durability can be selected for the use of combustion chamber through such specimen-level tests and the durability can be verified by the tests using the real scale combustion chambers.

Thermal Barrier Coating Durability Testing Trends for Thrust Chamber of Liquid-propellant Rocket Engine (액체로켓엔진 연소기 열차폐코팅 내구성 시험 기술동향)

  • Lee, Keum-Oh;Ryu, Chul-Sung;Lim, Byoung-Jik;Choi, Hwan-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2012.05a
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    • pp.603-615
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    • 2012
  • Durability testing method trends of the thermal barrier coating(TBC) for the combustion chamber of the liquid-propellant rocket engine has been investigated. Many types of the durability testing method such as the mechanical tests to measure surface cohesion force, the thermal fatigue tests with laser, furnace, burner or plasma, the small scale combustion tests using injectors, and the thermo-mechanical fatigue tests were observed. The TBC with sufficient durability can be selected for the use of combustion chamber through such specimen-level tests and the durability can be verified by the tests using the real scale combustion chambers.

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Thermal aging of Gr. 91 steel in supercritical thermal plant and its effect on structural integrity at elevated temperature

  • Min-Gu Won;Si-Hwa Jeong;Nam-Su Huh;Woo-Gon Kim;Hyeong-Yeon Lee
    • Nuclear Engineering and Technology
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    • v.56 no.1
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    • pp.1-8
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    • 2024
  • In this study, the influence of thermal aging on structural integrity is investigated for Gr. 91 steel. A commercial grade Gr. 91 steel is used for the virgin material, and service-exposed Gr. 91 steel is sampled from a steam pipe of a super critical plant. Time versus creep strain curves are obtained through creep tests with various stress levels at 600 ℃ for the virgin and service-exposed Gr. 91 steels, respectively. Based on the creep test results, the improved Omega model is characterized for describing the total creep strain curve for both Gr. 91 steels. The proposed parameters for creep deformation model are used for predicting the steady-state creep strain rate, creep rupture curve, and stress relaxation. Creep-fatigue damage is evaluated for the intermediate heat exchanger (IHX) in a large-scale sodium test facility of STELLA-2 by using creep deformation model with proposed creep parameters and creep rupture curve for both Gr. 91 steels. Based on the comparison results of creep fatigue damage for the virgin and service-exposed Gr. 91 steels, the thermal aging effect has been shown to be significant.

Fatigue Life Analysis on Multi-Stacked Film Under Thermal and Residual Stresses (열응력과 잔류응력하의 다층박막의 피로수명 해석)

  • Park Jun-Hyub
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.4 s.235
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    • pp.526-533
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    • 2005
  • Reliability problem in inkjet printhead, one of MEMS devices, is also very important. To eject an ink drop, the temperature of heater must be high so that ink contacting with surface reaches above $280^{o}C$ on the instant. Its heater is embedded in the thin multi-layer in which several materials are deposited. MEMS processes are the main sources of residual stresses development. Residual stress is one of the factors reducing the reliability of MEMS devices. We measured residual stresses of single layers that consist of multilayer. FE analysis is performed using design of experiment(DOE). Transient analysis for heat transfer is performed to get a temperature distribution. And then static analysis is performed with the temperature distribution obtained by heat transfer analysis and the measured residual stresses to get a stress distribution in the structure. Although the residual stress is bigger than thermal stress, thermal stress is more influential on fatigue life.

High Temperature Creep-Fatigue Behavior of 25Cr-13Ni Stainless Steel (25Cr-13Ni 스테인리스강의 고온 크리프-피로거동에 관한 연구)

  • Song, Jeon-Young;Ahn, Yong-Sik
    • Journal of the Korean Society for Heat Treatment
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    • v.28 no.2
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    • pp.68-74
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    • 2015
  • The low cycle fatigue (LCF) and creep-fatigue (hold time tension fatigue, HTTF) tests were performed on the modified 25Cr-13Ni cast stainless steel, which was selected as a candidate material for exhaust manifold in automotive engine. The exhaust manifold is subjected to an environment in which heating and cooling cycle occur due to the running pattern of automotive engine. Several types of fatigue behaviour such as thermal fatigue, thermal mechanical fatigue and creep-fatigue are belong to the main failure mechanisms. High temperature tensile test was firstly carried out to compare the sample with the traditional cast steel for the component. The low cycle fatigue and HTTF tests were carried out under the strain controlled condition with the total strain amplitude from ${\pm}0.6%$ to ${\pm}0.7%$ at $800^{\circ}C$. The hysteresis loops of HTTF tests showed significant stress relaxation during tension hold time. With the increase of tension hold time, the fatigue life was remarkably deceased which caused from the formation of intercrystalline crack by the creep failure mechanism.

Thermal Structural Analysis of the Engine Turbocharger under the Transient Temperature History Corresponding to the Motoring Fatigue Test (모터링 내구시험을 상사한 비정상 온도이력을 받고 있는 엔진 터보차져의 열적 거동해석)

  • Choi, Bok-Lok;Bang, In-Wan;Chang, Hoon
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.6
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    • pp.126-132
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    • 2011
  • Fatigue cracks of the turbocharger are often observed for high performance engines under thermal shock tests. Maximum exhaust gas temperature of recently developed gasoline engines could reach approximately $950^{\circ}C$. It's very important to estimate transient temperature histories during thermal shock cycles to predict the stress and the fatigue life of the turbocharger. With these temperature profiles, temperature-dependent material properties and boundary conditions, we could identify critical locations by the application of finite element simulation technologies. In this paper, we applied the reliable analysis approach to the actual turbocharger to predict the weak locations due to the repetitions of plastic strains and compared the results with the crack locations under physical engine test.

Extended Compliance Solution of ESET Specimen for Thermal fatigue Crack Growth Test (열피로 균열성장시험을 위한 ESET 시편의 확장된 컴플라이언스 해)

  • Lee, Ho-Jin;Kim, Maan-Won;Lee, Bong-Sang
    • Journal of the Korean Society of Safety
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    • v.20 no.1 s.69
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    • pp.62-67
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    • 2005
  • An eccentrically-loaded single edge crack tension specimen (ESET) is similar to a compact tension(CT) specimen loaded in tension-tension. The standard ESET specimen exhibits advantages over other types of cracked specimen, such as n, single-edge crack, and middle-crack tension specimen. The details of ESET specimen configuration, test procedure, and calculations are described in ASTM E647 standard. However, a difficulty in attaching COD gage to the knife-edge on the front foe of the specimen can be found when the size of ESET specimen is small for rapid cooling and heating in thermal fatigue testing. The finite element analysis is performed for the ESET specimen with projected knife-edge on the front foe and a crack-length-compliance equation is suggested for the new specimen configuration. Calibration test are conducted with 347 stainless steel to compare the measured crack length with the calculated crack length from the suggested compliance expression. The test results showed good agreements with those of analysis.