On the equivalence of mini-flat and cylindrical tensile geometries to extract hardening law and ductility of Eurofer97

Properties extracted from uniaxial tension provide fundamental information about the strength and ductility as the first input for the structural analysis, conventionally performed by means of finite element computations. In recent years, there has been a growing interest in evaluating the mechanical properties of materials using small specimens, especially in the nuclear industry due to limited volumes available in test facilities and limitations on wastes. The application of miniaturized flat sample geometries offers a number of advantages in terms of exposure to irradiation or extraction of samples using modern tools. However, the applicability of flat geometries should be validated.Here, the equivalence and interchangeability of miniaturized flat and cylindrical tensile samples for the extraction of the tensile properties are investigated by using a combined experimental-computational study. The emphasis is put on the determination of the post-necking properties. The experiments involve uniaxial tensile tests on Eurofer97 steel at various technologically relevant temperatures. Finite element (FE) simulations are performed with the parameters of a Gurson-type constitutive law including damage, identified based on the experimental data. For the flat tensile samples, the FE simulations reproduce the experimental data with an accuracy exceeding 95% attained for such important parameters as total elongation, reduction of area, and fracture strength. The application of the FE modelling to predict the tensile properties of cylindrical samples yields an accuracy between 80% and 95%. The reasons for the reduced accuracy are discussed and ascribed to a difference in the stress triaxiality distribution and, as a result, an overestimation of the fracture strain in the cylindrical geometry.

Automated summary

This article investigates the equivalence and interchangeability of miniaturized flat and cylindrical tensile samples for the extraction of the tensile properties. The experimental-computational study focuses on the determination of the post-necking properties. The results show that the finite element simulations accurately reproduce the experimental data for flat tensile samples, but have a reduced accuracy for cylindrical samples due to a difference in the stress triaxiality distribution.