Review of time-dependent fatigue behavior of structural alloys

Abstract “A review and assessment of time-dependent fatigue was needed to provide an understanding of time-dependent fatigue processes, to define the limits of our present knowledge, and to establish bases for the development of verified design methods for structural components and systems for operation at elevated temperatures. This report reviews the present state of understanding of that phenomenon, commonly called ‘creep fatigue’, and separates it into crack-initiation and crack-propagation processes. Criteria for describing material behavior for each of these processes are discussed and described within the extent of present knowledge, which is limited largely to experience with one-dimensional loading. Behaviors of types 304 and 316 stainless steel are emphasized. Much of the treatment of time-dependent failure presented here is new and of a developing nature; areas of agreement and areas requiring further resolution are enumerated.” These words are from the abstract of the report on a comprehensive study of time-dependent fatigue. This paper briefly reviews some of the contents and discusses important conclusions reached, especially in terms of current status and needs for additional work.