• Title, Summary, Keyword: Creep Potential

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Modeling of Anisotropic Creep Behavior of Coated Textile Membranes

  • Yu Woong-Ryeol;Kim Min-Sun;Lee Joon-Seok
    • Fibers and Polymers
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    • v.7 no.2
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    • pp.123-128
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    • 2006
  • The present study aims at characterizing and modeling the anisotropic creep behavior of coated textile membrane, a class of flexible textile composites that are used for moderate span enclosures (roofs and air-halls). The objective is to develop a creep model for predicting the lifetime of coated textile membrane. Uniaxial creep tests were conducted on three off-axis coupon specimens to obtain the directional creep compliance. A potential with three parameters is shown to be adequate for modeling the anisotropic creep behavior of coated textile membrane. Furthermore, a possibility of predicting the creep deformation of coated textile membrane in a multi-axial stress state is discussed using the three-parameter potential.

Thermal Aging and Creep Rupture Behavior of STS 316 (STS 316의 시효 열화 처리와 크리프 거동 특성)

  • 임병수
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.8 no.4
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    • pp.123-129
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    • 1999
  • Although type 316 stainless steel is widely used such as in reactors of petrochemical plants and pipes of steam power plants and s attracting attention as potential basic material for the fast breeder reactor structure alloys in nuclear power plants and is attracting attention as potential basic material for the fast breeder reactor structure alloys in nuclear power plants the effect of precipitates which form during the long term exposure at service temperature on creep properties is not known sufficiently. In this study to investigate the creep properties and the influence of prior aging on the microstructure to form precipitates specimens were first solutionized at 113$0^{\circ}C$ for 20 minutes and then aged for different times of 0 hr, 100 hrs, 1000 hrs and 2200 hrs at 75$0^{\circ}C$ After heat treatments tensile tests both at room temperature and $650^{\circ}C$ and constant load creep ruptuere tests were carried out.

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A Case study of Ground Treatment for Container Terminal Site Formation with Full Dredging and Replacement Method (완전준설 치환공법에 의한 컨테이너 부지조성 사례)

  • Hong, Eui;Sim Dong-Hyun
    • 기술발표회
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    • pp.235-247
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    • 2006
  • A ground treatment work for Hongkong container terminal yard is reported as a case study of site formation work with full dredging and replacement method. Ground treatment work adopting surcharge and deep compaction (vibroflotation) were applied to improve the sand creep potential. The sand creep parameter of 0 25% was assumed in design stage and improved up to 0.05% and 0.02% after surcharge and deep compaction respectively

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Creep behaviour of flexible adhesives

  • van Straalen, Ijsbrand J.;Botter, Erik;van den Berg, Arnold;van Beers, Peter
    • Journal of Adhesion and Interface
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    • v.5 no.2
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    • pp.5-14
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    • 2004
  • Since flexible adhesives are used more and more in structural applications, designers should have a better understanding of its behaviour under various conditions as ultimate load, fatigue load, long-term load and environmental conditions. This paper focuses on long-term load conditions and its effect on flexible adhesives. The creep properties of both PU (PolyUrethane) and SMP (Silyl Modified Polymers) adhesives used for identical applications are considered. To investigate the creep behaviour tests under various conditions were done. The results of those tests are presented and compared. To evaluate these results an empirical method is proposed and discussed. An example illustrates the potential of this method. It is also shown that with use of a probabilistic calibration technique this method results into a simple rule, which can be used to calculate the creep for practical applications. For the studied adhesives, the creep performance of the SMP adhesive is shown to be of the same level or slightly better than of the two PU adhesives. In addition to this empirical method, the principles of a more complex theoretical based method are introduced. The potential of this method is illustrated and future research activities are drawn.

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Electric potential redistribution due to time-dependent creep in thick-walled FGPM cylinder based on Mendelson method of successive approximation

  • Kheirkhah, S.;Loghman, A.
    • Structural Engineering and Mechanics
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    • v.53 no.6
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    • pp.1167-1182
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    • 2015
  • In this study, the stresses and electric potential redistributions of a cylinder made from functionally graded piezoelectric material (FGPM) are investigated. All the mechanical, thermal and piezoelectric properties are modeled as power-law distribution of volume fraction. Using the coupled electro-thermo-mechanical relations, strain-displacement relations, Maxwell and equilibrium equations are obtained including the time dependent creep strains. Creep strains are time, temperature and stress dependent, the closed form solution cannot be found for this constitutive differential equation. A semi-analytical method in conjunction with the Mendelson method of successive approximation is therefore proposed for this analysis. Similar to the radial stress histories, electric potentials increase with time, because the latter is induced by the former during creep deformation of the cylinder, justifying industrial application of such a material as efficient actuators and sensors.

A Study on High Temperature Crack Growth Behavior in 2.25Cr-lMo Steel Weldments at $550^{\circ}C$ ($550^{\circ}C$에서의 2.25Cr-1Mo 강 용접부의 고온 균열성장 거동에 관한 연구)

  • Kim, Ho-Kyung;Chung, Kang;Chung, Chin-Sung
    • Journal of Welding and Joining
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    • v.19 no.3
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    • pp.278-284
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    • 2001
  • Both creep deformation and creep crack growth experiments have been conducted on 2.25Cr-1Mo steel weldment in order to provided an information on residual life prediction of structural component weldment containing a crack. The stress exponent of creep deformation equation for the base metal and weldment at 823k were found to be 10.2 and 7.3, respectively. These two values could be assumed that dislocation climb processes are controlling the creep deformation of both materials. The creep rate of the weldment was very low, compared with that of base metal under the same applied stress. Whereas the creep crack growth rate of the weldment was almost twice higher than that of base metal under the fixed value of $C^*$. This may indicate that the weldment is stronger than the base metal in view of creep deformation and is brittle during creep crack growth due to the intrinsic microstructure of banite and relatively higher and Mn contents.

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Development of Small-Specimen Creep Tester for Life Assessment of High Temperature Components of Power Plant (발전소 고온부의 수명 평가를 위한 소형 시편용 크리프 시험기의 개발)

  • Kim, Hyo-Jin;Jeong, Yong-Geun;Park, Jong-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.10
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    • pp.2597-2602
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    • 2000
  • The most effective means of evaluating remaining life is through the creep testing of samples removed from the component. But sampling of large specimen from in-service component is actually impossible. So, sampling device and small-specimen creep tester have been applied. Sampling device has been devised to extract mechanically small samples by hemispherical, diamond -coated cutter from the surface of turbine rotor bores and thick-walled pipes without subsequent weld repairs requiring post weld heat treatment. A method of manufacturing small creep specimen, 2min gage diameter and 10min gage length, using electron beam welding to attach grip section, has been proven. Small-specimen creep tester has been designed to control atmosphere to prevent stress increment by oxidation during experiment. To determine whether the small specimens successfully reproduce the behavior of large specimens, creep rupture tests for small and large specimens have been performed at identical conditions. Creep rupture times based on small specimens have closely agreed within 5% error compared with that of large specimen. The errors in rupture time have decreased at longer test period. This comparison validates the procedure for fabricating and testing on small specimen. This technique offers potential as an efficient method for remaining life assessment by direct sampling from in -service high temperature components.

Constitutive Models for Final Stage Densification of Powder Compacts with Power-Law Creep Deformation (Power-law 크리프 변형을 따르는 분말 성형체의 말기 치밀화 모델)

  • Yang, Hoon-Chul;Kim, Ki-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.7
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    • pp.930-939
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    • 2004
  • Constitutive models for final stage densification of metal powder compacts with power-law creep deformation were investigated. The constitutive models were implemented into a finite element program (ABAQUS) by using user subroutine CREEP and, from FEM results, useful densification curves were obtained when hydrostatic and uniaxial stress were applied to the powder compacts at various pressures and temperatures. Because the densification behavior varied as the constitutive models, the equivalent stress surface on each constitutive equation was investigated to analyze the difference of densification behavior.

Creep behaviour of mudstone in the tertiary Duho Formation at Pohang basin (포항분지 제3기 두호층 이암의 크리프 거동)

  • 김광식;김교원
    • The Journal of Engineering Geology
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    • v.13 no.2
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    • pp.227-238
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    • 2003
  • Understanding of a creep behavior in rocks under a constant load, due to visco-elastic properties of rock, is an essential element to predict a long term ground deformation. In order to clarify the creep characteristics of the mudstone in Duho formation at Pohang basin, deposited during Tertiary, a series of laboratory tests including physical properties, unconfined compressive strength and uniaxial creep tests, was performed. The mudstone showed a higher creep potential due to 26% of clay minerals such as illite and chlorite. The unconfined compressive strength of the rock was $462{\;}kg/\textrm{cm}^2$ in average, and four creep tests were performed under constant stress of 40 to 70 % of the strength. The creep constants in the empirical and theoretical equations were deduced from the time-strain curves obtained from the tests. Among the several equations, the empirical equation proposed by Griggs and theoretical equation of Burger’s model are appreciated as the best one to express the creep behavior of the mudstone. Instantaneous elastic strain was linearly increased with stress level but strain velocity during the first creep is decreased with a similar pattern by time lapse regardless the stress level.

Undrained Creep Rupture of an Anisotropically Normally Consolidated Clay (이방정규압밀점토의 비배수크리프 파양)

  • Kang, Byung-Hee;Hong, Eui
    • Geotechnical Engineering
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    • v.9 no.4
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    • pp.55-64
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    • 1993
  • The Undrained creep tests on the normally consolidated clays with four different consolication ratios(c3c'/clc': 1.0, 0.7, 0.5, 0.4) were performed to investigate the effects of avisotropic consolidation on the undrained creep rupture behavior. The elapsed time to a certain minimum strain rate is decreased with decreasing the value of the consolidation pressure ratio, and the elapsed time to rupture for a certain minimum strain rate is also decreased with decreasing the ratio. The upper yield strength obtained from the equation suggested by Finn and Shead(1.) is coincided well with the creep strength irrespective of the magnitude of the consolidation pressure ratio, and the normallised upper yielding strength by mean confining pressure is decreased with increasing the consolidation pressure ratio. The critical strain for creep rupture, the strain at min. strain rate, is constant irrespective of the magnitude of creep stress, but it increased exponentially with increasing the ratio, It accordingly is dangerous that the potential of in-situ creep rupture is estimated only by the creep rupture test on the isotropically consolidated clay in case of K0-value below 1.0.

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