Investigation of mechanical properties of In Service Materials using small punch test

Abstract

quotThe small punch test (SPT) is a non-destructive and miniature specimen testing technique to estimate the preserved mechanical strength of an in-service system material in situ state to check its fitness for service. This technique was first attempted during late 1980 by many of the researchers. This test involves a miniature specimen size of and#61542;8mm x 0.5mm thick circular plate which can be easily extracted from in-service system without affecting in-service system s structural strength integrity. This test is widely explored as an alternate of traditional uniaxial tensile testing for mechanical characterisation to assess fitness of service of some of the critical product applications like, nuclear reactor, steam power plant etc. where larger bulk of material volume extraction is not possible to perform uniaxial tensile test. newline newlineDuring the SPT, a miniature specimen tightly clamped through dies and spherical tipped punch gradually indents it at certain force. The instantaneous indentation force, punch displacement, and specimen deformation due to indenting force, are continuously being measured. The measured data are outlined in form of force-specimen deflection (F-u) and force-punch displacement (F-v) as a SPT response. The uniaxial yield force F_e and ultimate force F_u are determined using proposed graphical approaches from the SPT responses. Later, such forces are post-processed to estimate uniaxial yield strength and#963;_y and ultimate strength and#963;_u utilising the empirical correlations which are available in the domain. newline newlineThe post-processing of SPT response toward accurate estimation of mechanical forces and strengths are very sensitive to adopted best-practices and empirical correlations so that there are many diverse opinions exist so that many of the standards were published to define a universally accepted approach for SPT-aided mechanical characterization. However, it was recognized that such standards were not concerned to practice a consistent approach while SPT response measurement and inventing best-f