高温押込みクリープ試験を用いたクリープ余寿命診断手法の提案

抄録

Creep remaining life assessment is one of important issues to maintain high-temperature components of aged thermal power plant. Our research group has developed the high-temperature indentation test to evaluate creep constitutive equation known as Norton's law. The creep coefficient k and creep exponent n in the creep constitutive equation can be accurately identified from the relationship between time and impression size marked on the specimen surface. In addition, a possibility of creep life prediction using the indentation test is expected. It has been thus reported that the creep exponent of an aged material increases monotonically with the operating time. In this study, alternative life assessment method is proposed based upon creep exponent n which was identified by the developed indentation test. First of all, uniaxial creep tests were conducted under two test temperatures in order to prepare each five specimens with different creep damage ratios, which are 0, 0.25, 0.50, 0.75 and 1, respectively. Subsequently, the indentation tests were conducted to identify the creep exponent n for each specimen. As a result, it was recognized that the creep exponent n increases monotonically with the creep damage ratio. These results provide us that the creep life can be appropriately predicted using relationship between the creep exponent n and the creep damage ratio φ.