A comprehensive solution to miniaturized tensile testing: Specimen geometry optimization and extraction of constitutive behaviors using inverse FEM procedure

摘要

Small specimens have been widely used in the mechanical testing for structural materials of nuclear reactors, due to the volume constraint of irradiation facilities and the stringent limits on specimen radioactivity. This article proposes an innovative two-round approach to optimize the design of dog bone typed small flat tensile specimens. Firstly, the specimen thickness was chosen from the lower bound in the literatures, and the width of the parallel section was optimized to reduce the difficulty for specimen handling. Secondly, four candidates for reduced parallel section length were experimentally tested with CLF-1 and QP980 steels, whose constitutive behaviors were extracted from the testing results by an automatic inverse FEM procedure; such specimen candidates were optimized by evaluating the repeatability of the testing results and the consistency of the constitutive behaviors with those of the standard specimen, respectively. The specimen geometry with a 2 mm long parallel section which has a thickness of 0.2 mm and a width of 1 mm, has the best performance and hence it is regarded as a preliminary optimization for the miniaturized tensile testing towards application in fusion irradiation. This study demonstrates the feasibility to drastically shorten the parallel section with the help of the inverse FEM procedure to extract material constitutive behaviors, when the specimen thickness cannot be further reduced due to the possible deviation from bulk properties. (C) 2017 Elsevier B.V. All rights reserved.