Requirements for and use of miniature test specimens to provide mechanical and creep properties of materials: a review

Abstract

The review is concerned with the use of miniature specimens to identify the mechanical/creep properties of metals and alloys. It is not intended to consider the nanoscales, which have been reviewed elsewhere, but focus on the size ranges and forms that are of use to areas such as alloy development, surveillance monitoring, effects of irradiation, properties of weld structures and remaining life. For many of these cases, there are technical advantages in the use of small specimens. Where possible, available reviews in this area are used and identified. The needs for small specimen sizes are considered, and the wide range of sizes of both conventional and more unusual specimen designs is reviewed. The potential effects of specimen size are considered: the microstructural features of the material, the effect of constraint and the actual region of the specimen that is undergoing deformation, and finally statistical approaches. The results of published studies are considered under the general groupings of yield/deformation behaviour, creep properties, toughness and fatigue, with an examination of the current state of interpretation of data from mini-specimens because interpretation is one of the key areas of interest. Finally, the current status of each area is considered, as certain designs of specimen will be better suited to answering specific technical questions. The need for standards for specific designs is also examined.