• Title/Summary/Keyword: Time-Temperature Parameter

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A Study of the Effect of Stress Waveform on the Behavior of High Temp. Fatigue Crack Propagation Using J Parameters (J파라미터를 이용한 고온피로균열전파 거동에 미치는 응력파형 영향의 연구)

  • Hur, Chung-Weon;Park, Won-Jo
    • Journal of the Korean Society of Safety
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    • v.15 no.2
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    • pp.8-12
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    • 2000
  • The fatigue crack propagation tests were performed in triangular and holding-time stress waveforms at $650^{\circ}C$. The behavior of fatigue crack propagation was investigated according to waveform. The analysis of high temperature fatigue crack propagation by the stress intensity factor range ${\Delta}K$, elastic fracture mechanics parameter, was not available. The behaviors of high temperature fatigue crack propagation by the J-integral(${\Delta}J_f$, J' and ${\Delta}J_c$), elasto-plastic fracture mechanics parameter, were investigated in a number of stress waveforms. The fast-fast waveform exhibited cycle-dependent(fatigue type), the slow-fast and the hold time with 500sec waveforms appear to be time-dependent(creep type) and the fast-slow and the hold time with 5, 25sec waveforms exhibited conbined behavior of both types(fatigue-creep conbined type).

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A Study on Response Time Index and Operating Time for Fusible Link Sprinkler Head (용융형 스프링클러 헤드의 응답시간 지수 및 작동시간에 관한 연구)

  • 이병곤;태순호
    • Journal of the Korean Society of Safety
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    • v.6 no.4
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    • pp.34-44
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    • 1991
  • In this study, the general solution of heat balance equation including conductive heat loss were suggested and were determined the constants with the results of experiment in hot tunnel in order to derive the general equation for the response time and to investigate the response time index which represent the characteristics of response of sprinkler head in actual fires. Two types of test were considered, the plunge test, in which the air temperature is represented by a step function, and the ramp test, in which the air temperature increases at a constant rate. As a result, simple equations were derived, which can be predicted the response time for the ramp type fire with the rate of temperature rise and gas velocity, for the plunge type fire with temperature and gas velocity. Also other useful data, such as the effective temperature, time constant, response time index and conduction parameter were obtained.

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Reliability Evaluation on Creep Life Prediction of Alloy 617 for a Very High Temperature Reactor (초고온 가스로용 Alloy 617의 크리프 수명예측 신뢰성 평가)

  • Kim, Woo-Gon;Park, Jae-Young;Kim, Seon-Jin;Hong, Sung-Deok;Kim, Yong-Wan
    • Korean Journal of Metals and Materials
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    • v.50 no.10
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    • pp.721-728
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    • 2012
  • This paper evaluates the reliability of creep rupture life under service conditions of Alloy 617, which is considered as one of the candidate materials for use in a very high temperature reactor (VHTR) system. A Z-parameter, which represents the deviation of creep rupture data from the master curve, was used for the reliability analysis of the creep rupture data of Alloy 617. A Service-condition Creep Rupture Interference (SCRI) model, which can consider both the scattering of the creep rupture data and the fluctuations of temperature and stress under any service conditions, was also used for evaluating the reliability of creep rupture life. The statistical analysis showed that the scattering of creep rupture data based on Z-parameter was supported by normal distribution. The values of reliability decreased rapidly with increasing amplitudes of temperature and stress fluctuations. The results established that the reliability decreased with an increasing service time.

A Study on Manufacturing of Plastic Injection Mold for Warpage Characteristics of Mobile Phone Cover (모바일폰 커버의 휨특성 평가를 위한 금형 제작에 관한 연구)

  • Kim M. Y.;Lee S. H.;Kwon C. O.;Kim O. R.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.09a
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    • pp.126-131
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    • 2005
  • In the present study, warpage characteristics of mobile phone cover through injection molding process were investigated by using design of experiments. Warpage in plastic injection molding process has a significant effect on quality of product. Effects of injection time, packing pressure, packing time, mold temperature ana melt temperature on warpage of mobile phone cover were considered by CAE analysis and experiment with Taguchi method. The degree of warpage for the injection molded product was measured by using three dimensional CMM. It was shown that temperature parameter has more significant effect on the warpage of mobile phone cover than pressure parameter.

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Thermomechanical Characteristics for Structural Material of Supersonic Vehicle (초음속 비행체 구조재료에 대한 열기계적 특성)

  • Kim, Jong-Hwan;Lee, Kee-Bhum;Lee, Kuong-Yong
    • Journal of the Korea Institute of Military Science and Technology
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    • v.8 no.2 s.21
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    • pp.77-87
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    • 2005
  • The thermomechanical characteristics were evaluated for 17-4PH stainless steel widely used in supersonic airframe subjected to both aerodynamic loading and heating. The thermomechanical tests were conducted under both elevated temperature and rapid heating condition from $1^{\circ}C/sec\;to\;28^{\circ}C/sec$. The thermomechanical behaviors under rapid heating were compared with those of elevated temperature after 1/2 hour exposure in terms of yield stress to investigate the influence of heating rates. A heating rate-yield temperature parameter was suggested for rapid heating based on time-temperature parameters, and master yield stress curve was obtained by using these parameters. The experimental results and methodology from this study can be used as basic engineering data when designing supersonic vehicle structures subjected to aerodynamic loading and severe heating environment.

Fuzzy Self-Organizing Control of Environmental Temperature Chamber (온도챔버의 퍼지 자동조정 제어시스템)

  • 김인식;권오석
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.31B no.1
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    • pp.34-40
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    • 1994
  • The design and implementation of a fuzzy self-organizing controller for an environmental temperature chamber is discussed. The chamber is a non-linear, time-variant system with delay-time and dead-time. And the parameter tuning is required in PI control when the performance degraded. However the proposed fuzzy-SOC monitors the performance of the process. modifies the data base, and performs the delay-time compensation based on the idealized process model. A series of experiments was performed for the conventional PI and the fuzzy-SOC. These experimental results show the usefulness of the fuzzy-SOC.

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Evaluation on the Creep Life Prediction Using Initial Strain Method (초기 연신율법을 이용한 크리프 수명예측 평가)

  • Kong, Yu-Sik;Lim, Man-Bae;Lee, Sang-Pill;Yoon, Han-Ki;Oh, Sae-Kyoo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.6
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    • pp.1069-1076
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    • 2002
  • The high temperature creep behavior of heat machine systems such as aircraft engines, boilers and turbines in power plants and nuclear reactor components have been considered as an important and needful fact. There are considerable research results available for the design of high temperature tube materials in power plants. However, few studies on the Initial Strain Method (ISM) capable of securing repair, maintenance, cost loss and life loss have been made. In this method, 3 long time prediction Of high temperature creep characteristics can be dramatically induced through a short time experiment. The purpose of present study is to investigate the high temperature creep lift of Udimet 720, SCM 440-STD61 and 1Cr-0.5Mo steel using the ISM. The creep test was performed at 40$0^{\circ}C$ to $700^{\circ}C$ under a pure loading. In the prediction of creep life for each materials, the equation of ISM was superior of Larson-Miller Parameter(LMP). Especially, the long time prediction of creep life was identified to improve the reliability.

Application of the Equivalent Point Method for Estimation of Kinetic Parameters (Kinetic Parameters 결정을 위한 Equivalent Point Method의 이용)

  • Rhim, Jong-Whan
    • Korean Journal of Food Science and Technology
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    • v.22 no.5
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    • pp.582-589
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    • 1990
  • A method for application of the equivalent time and temperature point for estimating kinetic parameters was proposed. The feasibility of the method was demonstrated with both theoretical and empirical kinetic data. The theoretical kinetic data were obtained from the arbitrarily chosen time-temperature data for three chemical reactions whose kinetics are well established. The experimental kinetic data were obtained for the acid (0.0005 N HCl) catalyzed hydrolysis of sucrose(2%). The activation energy and the frequency factor determined by the proposed method were $104.74{\pm}1.87kJ/mol\;and\;5.62{\times}10^{14}\;hr^{-1}$ respectively and the results agreed well with those obtained by a different method of kinetic parameter estimation, i.e. the linearly increasing temperature method.

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Two Factors Failure Model of Oil-Paper Insulation Aging under Electrical and Thermal Multistress

  • Li, Jian;Wang, Yan;Bao, Lianwei
    • Journal of Electrical Engineering and Technology
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    • v.9 no.3
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    • pp.957-963
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    • 2014
  • Converter transformers play important roles in high-voltage direct current transmission systems. This paper presents experimental and analysis results of the combined electrical and thermal aging of oil-impregnated paper at pulsating DC voltages. Breakdown voltages and time-to-breakdown of oil-paper specimens were measured by using short-time and constant-stress tests. The breakdown characteristics of combined electrical and thermal aging on insulation system were discussed. According to the relationship between failure time and aging temperature, the two-parameter Weibull model was improved. On the basis of the competing risk algorithm and the improved Weibull model, the two factors failure model was calculated. And the influence of temperature in the insulation system has been analyzed. This model performs better than the two-parameter Weibull model when both time and temperature are considered as variables in estimating the lifetime of oil-paper insulation.

Reliability Prediction of Long-term Creep Strength of Gr. 91 Steel for Next Generation Reactor Structure Materials (미래형 원자로 구조 재료용 Gr. 91 강의 장시간 크리프 강도의 신뢰성 예측)

  • Kim, Woo-Gon;Park, Jae-Young;Yin, Song-Nan;Kim, Dae-Whan;Park, Ji-Yeon;Kim, Seon-Jin
    • Korean Journal of Metals and Materials
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    • v.49 no.4
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    • pp.275-280
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    • 2011
  • This paper focuses on reliability prediction of long-term creep strength for Modified 9Cr-1Mo steel (Gr. 91) which is considered as one of the structural materials of next generation reactor systems. A "Z-parameter" method was introduced to describe the magnitude of standard deviation of creep rupture data to the master curve which can be plotted by log stress vs. The larson-Miller parameter (LMP). Statistical analysis showed that the scattering of the Z-parameter for the Gr. 91 steel well followed normal distribution. Using this normal distribution of the Z-parameter, the various reliability curves for creep strength design, such as stress-time temperature parameter reliability curves (${\sigma}$-TTP-R curves), stress-rupture time-reliability curves (${\sigma}-t_{r}-R$ curves), and allowable stress-temperature- reliability curves ([${\sigma}$]-T-R curves) were reasonably drawn, and their results are discussed.