Numerical evaluation of J-R curve using small punch test data

The miniaturized specimens are in use to determine mechanical properties of the materials, such as yield strength, ultimate tensile strength, and ductility. Use of such specimens is popular whenever the limited quantity of material is available for testing, such as aged/irradiated material. In this paper, six miniaturized small punch tests have been carried out for three materials, viz., T91, AISI403, 20MnMoNi55 which are commonly used as structural materials in nuclear reactors. The punch load v/s displacement data are collected up to fracture signified by a rapid drop in load carrying capacity of the specimens. The experimental data for each material is then used to evaluate yield strength and ultimate tensile strength making use of available correlations in the literature. These material data are then used to calculate Ramberg-Osgood hardening exponent leading to the generation of complete true stress-strain data. The next task is to determine Gurson-Tevergaard-Needleman (GTN) parameters of the materials which can simulate punch load v/s displacement. These GTN parameters along with true stress-strain data are then used to numerically generate J-R data of the materials by analyzing ASTM E1820 standard CT specimens. Calculated J-R data are then compared with the experimental values quoted in the literature. The methodology described in this paper has the potential to determine J-R data of aged/irradiated materials using small punch test.