• Title/Summary/Keyword: Time-Temperature Parameter

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Evaluation of Creep Fatigue Crack Growth Behavior of 9Cr Steel Employing Creep Reversal Parameter (크리프 역전 변수 도입에 의한 9Cr강의 크리프 피로 균열성장 거동의 평가)

  • Ma, Young-Wha;Baek, Un-Bong;Yoon, Kee-Bong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.7
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    • pp.1453-1460
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    • 2002
  • Creep-fatigue crack growth models have been proposed employing $(C_t)_{avg}$ as a crack tip parameter characterizing the time-dependent crack growth. The basic assumptions made in these previous models were ideal creep reversal conditions such as no creep reversal and complete creep reversal condition. Due to this assumption, the applicability of the models was limited since they did not consider partial creep reversal condition which is usually observed in many engineering metals at high temperature. In this paper the creep reversal parameter, Temperature;$C_R$, which was defined by Grover, is critically evaluated to quantity the extent of partial creep reversal at the crack tip. This approach does not rely on any simplifying assumptions regarding the extent of the amount of creep reversal during the unloading part of a trapezoidal fatigue cycles. It is shown that the $(C_t)_{avg}$ value calculated for 9Cr steel agrees well with the experimentally measured one. It is argued that the extent of improvement is not significant when the result is compared with that of the conventional model which has an assumption of full creep reversal behavior.

Variability of Short Term Creep Rupture Time and Life Prediction in Stainless Steels (스테인리스 강의 단시간 크리프 파단시간의 변동성과 수명예측)

  • Jung, Won-Taek;Kong, Yu-Sik;Kim, Seon-Jin
    • Journal of Ocean Engineering and Technology
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    • v.24 no.6
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    • pp.97-102
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    • 2010
  • This paper deals with the variability of short term creep rupture time based on previous creep rupture tests and the statistical methodology of the creep life prediction. The results of creep tests performed using constant uniaxial stresses at 600, 650, and $700^{\circ}C$ elevated temperatures were used for a statistical analysis of the inter-specimen variability of the short term creep rupture time. Even under carefully controlled identical testing conditions, the observed short-term creep rupture time showed obvious inter-specimen variability. The statistical aspect of the short term creep rupture time was analyzed using a Weibull statistical analysis. The effect of creep stress on the variability of the creep rupture time was decreased with an increase in the stress level. The effect of the temperature on the variability also decreased with increasing temperature. A long term creep life prediction method that considers this statistical variability is presented. The presented method is in good agreement with the Lason-Miller Parameter (LMP) life prediction method.

Assessment of Degradation Rate Coefficient and Temperature Correction Factor by Seasonal Variation of Concentration and Temperature in Livestock Wastewater Treatment in Field Scale (현장수준의 축산폐수처리에 있어서 계절별 농도 및 온도변화에 따른 분해반응계수 및 온도보정계수의 산정)

  • 박석환
    • Journal of Environmental Health Sciences
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    • v.22 no.2
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    • pp.90-95
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    • 1996
  • This study was performed to calculate the degration rate coefficient, operating parameters to meet the effluent standards, and the temperature adjustment coefficients to each parameter of pollution by seasonal variation of concentration and temperature of influent in livestock wastewater treatment by sequencing batch reactor process in field scale. The followings are the conclusions that were derived from this study. 1. In the field, temperature of livestock wastewater in reactor was 20.3$\circ$C in summer and 6.0$\circ$C in winter. The ratio of BOD:TKN: T-P in influent was 100:80:7. BOD loadings in winter and spring were 0.26 and 0.43 kg $BOD/m^3$ day, respectively. Those in summer and fall were 0.25 and 0.13 kg $BOD/m^3$ day, respectively. 2. The degradation rate coefficient for TKN was larger in summer and fall in which temperature was high than that in which temperature was high than that in winter and spring in which concentration was high. On the contrary, the phosphorus uptake rate was larger in winter and spring than that in summer and fall. 3. The hydraulic retention time in winter and spring was longer than that in summer and fall. Especially, in order to meet the standard for TKN of 120 mg/l in winter in which temperature of wastewater was 6.0$\circ$C, as the MLSS concentration was increased from 4, 000 to 7, 000 mg/l, the hydraulic retention time was increased from 212 to 121 hours. But, in order to shorten that less than 121 hours for the economical wastewater treatment, countermeasure to increase temperature of wastewater in the reactor should be considered. 4. the temperature adjustment coefficients for BOD, $COD_{Mn}$, TKN and T-P were 1.0241, 1.0225, 1.0541 and 1.0495, respectively. Namely, the treatment of TKN was most sensitively affected by temperature. For the purpose of the effective removal of nitrogen and phosphorus which are sensitive to temperature, it is necessary to keep the temperature of livestock wastewater more than 20$\circ$C which is the temperature of it in summer.

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High Temperature Creep Rupture Characteristics of Ni-Based Alloy718 Jointed by Friction Welding (마찰용접된 니켈기 초내열합금 Alloy718의 고온 크리프 파단 특성)

  • Kwon, Sang-Woo;Kong, Yu-Sik;Kim, Seon-Jin
    • Journal of Ocean Engineering and Technology
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    • v.22 no.6
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    • pp.58-63
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    • 2008
  • The short-term high temperature creep rupture behavior of Ni-based Alloy718 steels jointed by friction welding wasinvestigated at the elevated temperatures of 550 to $700^{\circ}C$ under constant stress conditions. The creep rupture characteristics such as creep stress, rupture time, steady state creep rate, and initial strain were evaluated. Creep stress has a quantitative correlation between creep rupture time and steady state creep rate. The stress exponents (n, m) of the experimental data at 550, 600, 650 and $700^{\circ}C$ were derived as 26.1, -22.4, 22.5, -18.5, 17.4, -14.3 and 6.9, -8.1, respectively. The stress exponents decreased with increasing creep temperature. The creep life prediction was derived by the Larson-Miller parameter (LMP) method and the result equation obtained is as follows: T(logtr+20)=-0.00148${\sigma}^2$-3.089${\sigma}$+23232. Finally, the results were compared with those of the base metal for Alloy718.

Creep-Life Prediction and Standard Error Analysis of Type 316LN Stainless Steel by Time-Temperature Parametric Methods (시간-온도 파라미터 방법에 의한 Type 316LN 강의 크리프 수명 예측과 표준오차 분석)

  • Yoon Song Nam;Ryu Woo Seog;Yi Won;Kim Woo Gon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.1 s.232
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    • pp.74-80
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    • 2005
  • A number of creep rupture data for type 316LN stainless steels were collected through literature survey or experimental data produced in KAERI. Using these data, polynomial equations for predicting creep life were obtained by Larson-Miller (L-M), Orr-Sherby-Dorn (O-S-D) and Manson-Haferd (M-H) parameters using time-temperature parametric (TTP) methods. Standard error of estimate (SEE) values for the each parameter was obtained with different temperatures through the statistical process of the creep data. The results of L-M, O-S-D and M-H methods showed good creep-life prediction, but M-H method showed better agreement than L-M and O-S-D methods. Especially, it was found that SEE values of M-H method at $700^{\circ}C$ were lower than that of L-M and O-S-D methods.

Creep Life Prediction of Friction Welded Joints (Cu-Alloy/STS316L) for Nuclear Power Plant (원자력 발전소용 마찰용접재 (Cu합금/STS316L)의 크리프 수명예측)

  • 유인종;공유식;오세규;김선진
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2001.10a
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    • pp.258-263
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    • 2001
  • In this paper, the real-time prediction of high temperature creep life was carried out for the friction welded joints of dissimilar heat resistintg steels (CulCr0.5Zr-STS316L). Various life prediction methods such as LMP (Larson-Miller Parameter) and ISM (initial strain method) were applied. The creep behaviors of those steels and the welds under static load were examined by ISM combined with LMP at 300, 400 and 50$0^{\circ}C$, and the relationship between these two methods was investigated. A real-time creep life (tsub/r/, hr) prediction equation by initial strain ($\varepsilon_0$, %) under any creep stress ($\sigma$, MP$\alpha$) at any high temperature (T, K) was developed

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An Analytical Investigation of a Hydraulic Clutch System of Powershift Transmission (파워시프트 변속기 유압클러치시스템의 해석적 연구)

  • Lee, J.C.
    • Transactions of The Korea Fluid Power Systems Society
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    • v.6 no.1
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    • pp.25-31
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    • 2009
  • This study presents an analytical model of hydraulic clutch system of a power shift transmission to analyze pressure modulation characteristics. A typical hydraulic clutch system was modeled by using AMESim in which the parameters of major components were measured for simulation. Test apparatus was established using the components of power shift and power shuttle clutches with instrumental equipment. The results of simulation and experiment were so close that the proposed analytical model in this study was validated. However the cylinder model analogized clutch dynamics need to be improved in future study. The effects of parameters of orifice diameter, accumulator stroke and oil temperature on pressure modulation were analyzed respectively. The results of parameter sensitivity analysis show that modulation time and set pressure can be easily adjusted by changing parameter values. It is also found that the hydraulic clutch system used in this study is so susceptible to oil temperature that cooling equipment is necessary.

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Effect of heat treatment on mechanical properties of overlay welds (육성 용접부의 기계적 성질에 미치는 열처리조건의 영향)

  • 이기호;김기철;윤의박
    • Journal of Welding and Joining
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    • v.7 no.4
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    • pp.30-37
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    • 1989
  • Effect of heat treatment on mechanical properties of an overlay weldment was investigated. Over welding was carried out on the structural C-Mn mild steel substrate to take required test specimens. Shielded metal arc welding process with 13Cr-0.2Ni stick electrode was applied. The heat treatment temperatures and holding times were $450{\circ}C., 550{\circ}C., 650{\circ}C., 750{\circ}C., 850{\circ}C.$ and 0.5hr, 2hr, 10hr, respectively. Mechanical tests and microscopic inspection were also carried out to investigate welds soundness. Test results indicated that carbon migration was dominant near bonded zone. At temperature of around 650.deg. C, carburized layer and decarburized layer were formed remarkably along overlay welds region and C-Mn mild steel region, respectively. The wideth of these layers became wider with increasing heat treatment temperature and/or holding time at the elevated temperature, and this relationship agreed with Larson-Miller parameter. Side bending test results demonstrated that the crack free region of overlay welds could be deduced from the relationship between temperature and holding time.

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Improvement of Long-term Creep Life Prediction Method of Gr. 91 steel for VHTR Pressure Vessel (초고온가스로 압력용기용 Gr. 91 강의 장시간 크리프 수명 예측 방법 개선)

  • Park, Jae-Young;Kim, Woo-Gon;EKAPUTRA, I.M.W.;Kim, Seon-Jin;Kim, Min-Hwan
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.10 no.1
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    • pp.64-69
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    • 2014
  • Gr. 91 steel is used for the major structural components of Generation-IV reactor systems, such as a very high temperature reactor(VHTR) and sodium-cooled fast reactor(SFR). Since these structures are designed for up to 60 years at elevated temperatures, the prediction of long-term creep life is important for a design application of Gr. 91 steel. In this study, a number of creep rupture data were collected through world-wide literature surveys, and using these data, the long-term creep life was predicted in terms of three methods: the single-C method in Larson-Miller(L-M) parameter, multi-C constant method in the L-M parameter, and a modified method("sinh" equation) in the L-M parameter. The results of the creep-life prediction were compared using the standard deviation of error value, respectively. Modified method proposed by the "sinh" equation revealed better agreement in creep life prediction than the single-C L-M method.