A Study on Thermal Fatigue of Circular Disk : in connection with the strength of Gas Turbine Disk

抄録

The analytical and experimental results of thermal fatigue of a circular disk of structural carbon steel are presented. The periphery of the disk is cycled between two programmed temperature levels, while a water cooled sink at the inner radius is kept at lower temperature level. (1) Unsteady elasto-plastic thermal stress and the strain in the disk specimen calculated from the measurement of radial temperature distribution on the disk are in good agreement with the experimental results, in both the measurement of the diametral displacement and the X-ray residual stress measurement. (2) Number of cycles to initiation of thermal crack in the disk is predicted from the uniaxial thermal fatigue test data on the common basis of the equivalent total strain range of Mises' criterion. The propagation rate of thermal crack is also predicted on the basis of product of the rate (dl/dN) with the number of cycles N at a prescribed crack length l.