The Influence of Both Testing Environment and Fillet Radius of the Die Holder on the Rupture Life of Small Punch Creep Tests

概要

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The small punch (SP) creep test has been proposed as a semi destructive testing methodology to examine the residual creep life of high temperature components. A series of SP creep tests were conducted on low alloy steel at 600°C both in air and in high vacuum to investigate the influences of both testing environment and the fillet radius of the lower die holder on the SP creep rupture life. The thickness of the oxide scale on the SP creep specimen in air increased with the test duration, <I>e.g</I>., about 30µm in thickness after a 400 hour exposure. The SP creep rupture life in air reduced to a half of the life in vacuum due to an increase in the actual stress in the specimen and also the coefficient of friction. In addition, the magnitude of the fillet radius at the lower die holder also affected the SP creep rupture life. The influence of the fillet radius on the SP creep rupture life was studied both experimentally and numerically. The SP creep rupture life with a smaller fillet radius of the lower die holder had twice the rupture life compared to that with a larger fillet radius. This effect was also demonstrated by the FE analysis.