Development of Creep Damage Evaluation Method for Cr-Mo-V Steel Forgings (2nd Report, Evaluation of Grain-Boundary Damage for Creep and Creep-Fatigue Situations)

In the previous report, creep damage evaluation method was studied for creep and creep-fatigue situations of Cr-Mo-V rotor steel and the stress-strain equations were devised by trial and error to simulate the creep and creep-fatigue behavior. However, to simulate the experimentally obtained behavior...

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Bibliographic Details
Published inTransactions of the Japan Society of Mechanical Engineers Series A Vol. 68; no. 670; pp. 985 - 992
Main Authors IKUNO, Takeshi, TANAKA, Kenichi, UEMATSU, Mikio
Format Journal Article
LanguageJapanese
Published The Japan Society of Mechanical Engineers 25.06.2002
Subjects
Creep
Creep-Fatigue
Grain-Boundary Sliding
Life Prediction
Statistical Treatment
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Summary:In the previous report, creep damage evaluation method was studied for creep and creep-fatigue situations of Cr-Mo-V rotor steel and the stress-strain equations were devised by trial and error to simulate the creep and creep-fatigue behavior. However, to simulate the experimentally obtained behavior of the grain-boundary cavity, further improvement must be applied to the equations. In this report, it is assumed that grain-boundary sliding is not only caused by creep strain but the effect of plastic strain must be considered, and inelastic strain is composed of 5 components i.e. εbpl, εbcr, εpl, εcr, and εdp, where εbpl and εbcr are the strains due to grain-boundary sliding, εpl, εcr and εdp are the strains due to the deformation of grains. Considering the inequality of each strain component and the inner stresses due to inharmonious values of components, new improved stress-strain equations were devised. The result of simulation shows good agreement with the result of experiment in creep deformation, creep-fatigue deformation, creep rupture behavior and cavity behavior on the grain-boundary, but the agreement with the number of cycles to failure and stress relaxation behavior in the strain-cycling tests with hold time is not enough. This may suggest that the decrease of the number of cycles to failure is caused by inelastic strain with surface oxidation etc. during the hold time rather than the accumulation of grain-boundary sliding.
ISSN:0387-5008
1884-8338
DOI:10.1299/kikaia.68.985