The Small Punch Test a Viable Alternate for In-service Components Preserved Strength Estimation

The small punch test (SPT) is a miniature specimen testing technique to extract the mechanical strength characterization of the in-service component—to determine its preserved strength and fitness-for-service. This technique delivers a convincing test outcome inline to conventional testing using a universal testing machine. The bulk material to retrieve from the in-service component for testing is quite challenging without compromising the structural strength integrity so this technique comes in handy to serve the purpose. During the SP testing, the miniaturized specimen is indented using a rigid ball punch, and the specimen’s load–displacement response is measured simultaneously. Such load–displacement response is post-processed further to determine the preserved strength parameters to assess the remaining life of the system to be fit for service. During the last couple of decades, numerous research advancements are made and several researchers have proposed various graphical and analytical approaches to improve the strength determination and mechanical characterization practice. However, many diverse opinions emerged in the efforts to formulate the reliable and universal mechanical characterization approach, using the SPT load–displacement data. This paper attempts to summarize the latest developments which are made and verifying the viability of popular graphical and analytical approaches for non-irradiated ductile iron, 65-45-12 material which is extracted from the in-service general-purpose mechanical system. It is also outlined the certain challenges and potential scope of improvement for SPT technique.