高温高速回転体のクリープについて

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In gas turbines the rotor disks are highly stressed by centrifugal force caused by high speed rotation and are required to run for a long time at high temperature. So it is important for designers to predict the stress and the creep strain. Research on the creep of rotating disk, both theoretical and experimental, is indispensable for development of gas turbine and many theoretical papers have been published. But, as for experimental papers, the number is quite small, as the experiment necessitates complicated methods and is expensive and moreover requires time and efforts. Wahl has developed an analytical study on steady state creep of rotating disks extending Bailey's method. In this study, creep rate at the given temperature is assumed to be a function of stress multiplied by a function of time i.e.ε=F(σ)f(t) and as a key expression between stress and creep rate the power function relation i.e. F(σ)=σ^n is adopted. Two dimensional stress state is assumed because axial stress is thought negligible as compared with radial and tangential stresses which are constant across the thickness of the disk. Elastic and transient creep strains are assumed to be negligible as compared with the steady state creep strain. Calculations are carried out in the following three cases : (1) Mises criterion and Mises flow rule, (2) Tresca criterion and Mises flow rule and (3) Tresca criterion and its associated flow rule. The analytical results have been compared with the experimental results carried out by him and his collaborators. In the experiments, allegheny 418 stainless steel disks (12% Cr, 3%W) were tested at an uniform temperature of 1000゜F (538℃), and the test time exceeded 900 hours. Disks were 12 inches (305 mm) O.D., 2.5 inches (63.5 mm) I.D. and 1 inch (25.4 mm ) in thickness. According to him, the analytical results obtained by means of Tresca criterion and its associated flow rule generally showed the closest agreement with the test data. Based upon this result he is continuing the analysis further.
社団法人日本材料学会の論文
1961-03-15

高温高速回転体のクリープについて

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