JSME International Journal Series A Solid Mechanics and Material Engineering
Online ISSN : 1347-5363
Print ISSN : 1344-7912
ISSN-L : 1344-7912
Volume 45, Issue 1
Special Issue on Creep and Fatigue at Elevated Temperatures
Displaying 1-18 of 18 articles from this issue
Special Issue on Creep and Fatigue at Elevated Temperatures
PAPERS
  • Yoko YAMABE-MITARAI, Shizuo NAKAZAWA, Hiroshi HARADA
    2002 Volume 45 Issue 1 Pages 2-7
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    The microstructure stability and creep properties of Ir-base refractory superalloys (It-Nb and Ir-Zr) with an fcc and L12 two-phase structure were investigated. An orderly arrayed structure composed of cuboidal coherent L12 precipitates was observed in the Ir-Nb alloys. By a different heat treatment, a maze structure and a discontinuous coarsened lamellar structure were obtained in the Ir-Zr alloys. Creep behavior was investigated for samples with these three kinds of microstructure between 1500 and 1800°C. The creep behavior was explained according to microstructural changes before and after creep.
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  • Yuefeng GU, Yoko YAMABE-MITARAI, Shizuo NAKAZAWA, Hiroshi HARADA
    2002 Volume 45 Issue 1 Pages 8-13
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    The compression properties and creep behaviors of the Ni added Ir85Nb15 alloys were investigated by compression tests in air and vacuum. X-ray diffraction, transmission microscopy and scanning electron microscopy were conducted to characterize the microstructure and lattice misfit change by the addition of Ni in Ir85Nb15 alloy. The results reveal that Ni addition can improve the yield strength of Ir85Nb15 alloy at room temperatures. 1 atomic percent Ni addition can raise creep resistance of Ir85Nb15 alloy two orders of magnitude. Basing on the results, the relationship among the Ni addition, the lattice misfit, microstructure development, and the creep behavior in Ni added Ir85Nb15 alloys is discussed in this paper.
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  • (An Assessment on Helium Embrittlement Resistance)
    Norikazu YAMAMOTO, Yoshiharu MURASE, Johsei NAGAKAWA, Kiyoyuki SHIBA
    2002 Volume 45 Issue 1 Pages 14-19
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    Mechanical response against transmutational helium production, alternatively susceptibility to helium embrittlement, in a nuclear fusion reactor was examined on 8Cr2WVTa martensitic steel, a prominent structural candidate for advanced fusion systems. In order to simulate DEMO (demonstrative) reactor environments, helium was implanted into the material at 823K with concentrations up to 1000appmHe utilizing an α-beam from a cyclotron. Creep rupture properties were subsequently determined at the same temperature and were compared with those of the material without helium. It has been proved that helium caused no meaningful deterioration in terms of both the creep lifetime and rupture elongation. Furthermore, failure occurred completely in a transgranular and ductile manner even after high concentration helium introduction and there was no symptom of grain boundary decohesion which very often arises in helium bearing materials. These facts would mirror preferable resistance of this steel toward helium embrittlement.
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  • Feng TANG, Shizuo NAKAZAWA, Masuo HAGIWARA
    2002 Volume 45 Issue 1 Pages 20-24
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    For the purpose of studying the creep behavior of orthorhombic Ti2AlNb (O-phase) based alloys, nine O-based alloys modified by V, Mo, or W were prepared. These alloys were heat-treated under various conditions. The creep tests were carried out at 650-750°C/310MPa in air, using a dead-weight creep-rupture machine. The activation energy of creep was calculated to be 327 to 416kJ/mol, which showed that the creep process was controlled by a dislocation climb. The alloys modified by W exhibited lower steady-state creep rates and longer transient times than the alloys modified by Mo and V, which is thought to be due to the lower diffusion rate of W in O-based alloys. The transformation of B2 phase into O phase during creep test runs at temperatures lower than the aging temperature was responsible for the large transient creep strain in a B2+O alloy. The effect of precipitate size on creep behavior is discussed.
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  • Yoshiaki TODA, Kazuhiro SEKI, Kazuhiro KIMURA, Fujio ABE
    2002 Volume 45 Issue 1 Pages 25-29
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    Effects of W and Co on microstructure of Co free 0.1C-15Cr-1Mo-3W-0.2V-0.05Nb-0.07N-0.003B (mass%) steel has been investigated, and a correlation between microstructure and creep strength property has been discussed. Time to rupture of 6W-3Co steel, in which W content was increased from 3 to 6mass% and 3mass%Co was added, was about 100 times longer than that of 3W-0Co base steel at 923K-100MPa and was almost the same as that of the conventional tempered martensitic creep resistant steel of NF616 steel. It has been found that the increase in W content and the addition of Co increases a number of coarse block type precipitates and promotes a precipitation of fine particles within grain, respectively. Furthermore, a large number of needle or disk-like fine particles aligned in a certain crystallographic orientation within grain has been observed in the creep ruptured steel containing high W and Co. It has been concluded that a remarkable increase in creep strength by the addition of W and Co is obtained by a combination of increase in an amount of coarse precipitates and a distribution of needle or disk-like fine particles within grain.
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  • Shin-ichi KOMAZAKI, Shigeo KISHI, Tetsuo SHOJI, Tetsuo KUMAZAWA, Kojir ...
    2002 Volume 45 Issue 1 Pages 30-38
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    The influence of pre-aging on creep rupture strength has been investigated to understand the creep damage mechanism of tungsten alloyed 9%Cr ferritic steel KA-STBA29/KA-STPA29. Additionally, we have also examined changes in strengthening factors during creep and thermal aging by a nano-indentation test. Experimental results revealed that the creep rupture strength of thermally aged materials decreased with prolonged pre-aging and that the decrease in solid-solution strengthening due to Laves phase precipitation was mainly responsible for this reduction of creep rupture strength. Based on the results, an electrochemical nondestructive procedure, which quantitatively detected the amount of Laves phase, has been proposed to evaluate creep damage accumulation in the steel. By using this electrochemical method and a newly proposed parameter based on kinetics of Laves phase precipitation, a testing temperature or applied stress of creep-damaged materials can be nondestructively estimated with relatively high accuracy.
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  • Yoshikazu YOKONO, Yoshihiro NAGANO, Kazuhiro MUKAI, Takuichi IMANAKA
    2002 Volume 45 Issue 1 Pages 39-45
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    Creep has been one of the most concerned matters on high temperature components of thermal power plants, petrochemical plants, oil refineries and so on. In present study, leaky surface acoustic wave (LSAW) has been applied to detect and evaluate the creep. LSAW signals with broad-band frequency generated by large-aperture-angle line-focus transducer were analyzed. The feature parameters of LSAW pulse both in time domain and in frequency domain such as amplitude of signal and ultrasonic power spectrum vary with creep process. Particularly high frequency components of LSAW attenuate through the mechanism of sound wave scattering by creep voids and cavities. Consequently ultrasonic spectroscopy technique can be expected to be available for deducing the state of deterioration in material quantitatively on the basis of correlation between microstructure in long-term operation at high temperature and ultrasonic propagation characteristics theoretically and practically.
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  • Jean-Bernard VOGT, José LEON SOSA, Sylvie ARGILLIER
    2002 Volume 45 Issue 1 Pages 46-50
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    The paper aims to analyse the high temperature low cycle fatigue behaviour of 2.25Cr1Mo steels that have been exposed in service at 565°C for about 110000h and 160000h. The volumic fraction of ferrite and bainite and the effect of the in-service long term ageing are analysed. Under strain controlled tests at 565°C in air, cyclic hardening is promoted by a large volumic fraction of ferrite. With a volumic fraction of 35% ferrite, a softening is favoured but the intensity and the rate are controlled by the state of bainite. Long term aged bainite promotes a softening of the steel. However, fatigue resistance did not appear to depend strongly on the microstructure because of the marked oxidation. Tests carried out in vacuum at a reduced pressure of 10-4Pa result in much longer fatigue lives than in air. At low strain amplitude, the fatigue resistance in vacuum is increased with a 65% bainite volumic fraction.
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  • Ikuo IOKA, Yukio MIWA, Hirokazu TSUJI, Minoru YONEKAWA, Fumiki TAKADA, ...
    2002 Volume 45 Issue 1 Pages 51-56
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    The low cycle creep-fatigue test with tensile strain hold of the austenitic stainless steelirradiated to 2 dpa was carried out at 823K invacuum. The applicability of creep-fatigue life prediction methods to the irradiated specimen was examined. The fatigue life on the irradiated specimen without tensile strain hold time was reduced by a factor of 2∼5 in comparison with the unirradiated specimen. The fraction of intergranular fracture increased with increasing strain hold time. The decline in fatigue life of the irradiated specimen with tensile strain hold was almost equal to that of the unirradiated specimen. For the irradiated specimen, the time fraction damage rule trends to yield unsafe estimated lives and the ductility exhaustion damage rule trends to yield generous results. However, all of data were predicted within a factor of three on life by the linear damage rule.
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  • Yichun ZHOU, Toshiyuki HASHIDA
    2002 Volume 45 Issue 1 Pages 57-64
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    This paper presents an experimental investigation on the thermal fatigue failure in thermal barrier coating (TBC) system at high temperature. The thermal fatigue failure was induced by temperature gradient along TBC system thickness direction and oxidation between TBC and bond coat. Laser heating method was employed to simulate the operating state of TBC system. The non-destructive evaluation methods such as acoustic emission (AE) and impedance spectroscopy (IS) were used to examine the evolution of TBC system damage. Both micro-observation and acoustic emission (AE) detection revealed that the fatigue damage consisted of vertical crack in the top coat layer and interface delamination between the top and bond coat. The life of thermal fatigue was shown to be reduced by the formation of alumina at interface. It was also found that the temperature gradient between the inner and outer surface of specimen accelerated the growth of alumina layer.
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  • Kwang Soo KIM, Chul HAN
    2002 Volume 45 Issue 1 Pages 65-71
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    Rate and non-rate parameters are examined for correlation of time-dependent crack growth rates under static control conditions. Experimental data on single edge notch specimens of IN718 at 593°C, compact tension specimens of stainless steel 304 at 538°C and X20CrMoV 12 1 steel at 545°C are used to examine the performance of rate parameters Cpc, J^·, J·* and non-rate versions of these parameters which are computed either from approximate equations or finite element analyses. It is found that rate parameters can correlate time-dependent crack growth rates whether the crack tip field is dominated by plasticity or by creep. Non-rate parameters are found inadequate in either circumstance.
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  • Andreas WICHTMANN
    2002 Volume 45 Issue 1 Pages 72-76
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    The application of creep damage evaluation in the design process of steam turbine components at elevated temperatures is discussed. The focus is on micromechanical methods accounting for the void growth in the creep range of ferritic steels (e. g. 1%-Cr steel). The main emphasis is on the change of void growth rate under multi-axial hydrostatic tension stress states. A commonly used calculation method, accounting for the degradation of deformation capacity due to void growth, is based on the work of Cocks and Ashby(1). The foundations and assumptions of this method will be discussed and the application in the design process will be shown. Based on this, an outline for a modified procedure will be presented. The comparison to experimental results shows the applicability of the modified method. A proposal for a calculation procedure using the basic evolution laws of void growth and strain rate shows the possibility of future development.
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  • Holm ALTENBACH, Konstantin NAUMENKO
    2002 Volume 45 Issue 1 Pages 77-83
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    Modern design rules for thin-walled structures which operate at elevated temperatures are based on the demand that the creep and may be the damage behaviour should be taken into account. In the last four decades various models including the scalar or tensor valued hardening and damage variables are established. These models reflect the influence of the deformation or the damage induced anisotropy on the creep response. One problem in creep analysis of thin-walled structures is the selection of the structural mechanics model which has to be adequate to the choice of the constitutive equations. Considering complex loading conditions the structural mechanics model has to reflect for instance the different constitutive behaviour in tension and compression. Below the applicability of classical engineering models for beams, plates and shells to the creep-damage analysis is discussed. It will be shown that a first improvement of the classical approach can be given within the assumptions of the first order shear deformation theory. Based on the beam equations we demonstrate that the shear correction factors have to be modified within the time-step analysis.
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  • Thomas H. HYDE, Anas YAGHI, Adib A. BECKER, Peter G. EARL
    2002 Volume 45 Issue 1 Pages 84-89
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    This paper is concerned with the creep analysis of pressurised pipe bends in which ovality of the circular cross-section is considered. A creep continuum damage mechanics analysis is performed using the Finite Element method. The failure times and failure positions are predicted and compared to steady-state creep solutions. A comparison of the two solutions shows that the steady-state creep solutions for failure times are conservative compared to the damage solutions.
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  • David R. HAYHURST, Man Tak WONG, Farid Vakili-TAHAMI
    2002 Volume 45 Issue 1 Pages 90-97
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    Techniques are reviewed for the calibration of constitutive relationships for the different phases of the weld. It is shown how the calibration is carried out using property ratios, and a knowledge of the constitutive equations of the parent material. The results of CDM analyses, obtained using the two-dimensional solver Damage XX, are reviewed for: a butt-welded pipe at 565°C; and, a welded cylinder-sphere pipe intersection at 590°C. Results are then presented of a three-dimensional CDM solution for a three-degree slice of the welded cylinder-sphere pipe intersection, and shown to be in close agreement with the two-dimensional, Damage XX, solution. Then the paper examines damage growth at a constant temperature of 590°C in a ferritic steel butt-welded pipe subjected to a combined constant internal pressure of 4MPa and a constant global bending moment of 49kNm. The CDM results for a three-dimensional analysis are compared with qualitative experimental results, and good correlation is indicated.
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  • David A. WOODFORD
    2002 Volume 45 Issue 1 Pages 98-103
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    This paper describes developments in the use of the high-precision stress relaxation test (SRT) as a basis for accelerated creep strength evaluation. In tests lasting less than one day a creep rate range of about five decades may be covered. It is shown how the approach is especially useful for superalloys and their application in combustion turbines. Using creep rate data, derived from the SRT tests, for conventionally cast, directionally aligned and monocrystalline alloys, a new framework for design and life management is described. By parameterizing the results over a range of temperature it is possible to attain design stress levels in less than a week of testing. The test may be used to determine the effect of microstructural features such as grain size and grain orientation, thermal-mechanical exposure conditions, test specimen section size, and the effect of location within a component.
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  • Yuji KURATA, Teiichiro SAITO, Hirokazu TSUJI, Tamao TAKATSU, Masami SH ...
    2002 Volume 45 Issue 1 Pages 104-109
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    A series of weldability and creep tests of the weld metals were conducted to develop a filler metal with excellent weldability and high creep strength of the weldments of Ni-Cr-W superalloy. Contents of minor elements have a large effect on susceptibility to cracking in weldments. In particular, Zr, B, Y and Nb make the susceptibility to cracking high and addition of optimum contents of Ti or Mg reduce it slightly. A good correlation between values of the CSC (coefficient of susceptibility to cracking) of the filler metals and the weldability is recognized. On the basis of the knowledge, a filler metal with excellent weldability was developed for the Ni-18.5Cr-21W superalloy. The weld metal prepared using the developed wire possesses the creep rupture strength almost equal to that of the base metal which has a creep rupture strength above 9.8MPa for a 1×105h life at 1000°C.
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  • Tetsuo ISHITSUKA, Hiroyuki MIMURA
    2002 Volume 45 Issue 1 Pages 110-117
    Published: 2002
    Released on J-STAGE: May 11, 2004
    JOURNAL FREE ACCESS
    An 18Cr-9Ni-W-Nb-V-N austenitic stainless steel tube for thermal power boilers has been newly developed. The high temperature mechanical properties and corrosion resistance of the steel were investigated. The creep rupture strength of the developed steel is about 1.5 times as high as that of SUS347HTB, and is almost the same as that of Ka-SUS310J2TB at 650°C. This excellent creep strength of the steel is mainly due to solid solution strengthening by tungsten and nitrogen, and precipitation strengthening by nitrides of niobium and vanadium. The carbon content of the steel is reduced to 0.03% to improve intergranular corrosion resistance. The steam oxidation resistance and the high temperature corrosion resistance of the tube are almost the same as those of SUS347HTB. Weldability of the developed steel is superior to that of SUS304HTB and SUS310TB. Thus the developed steel is suitable for use as a material for superheater and reheater tubes of thermal power boilers.
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