The effect of the inhomogeneous distribution of ovalization-induced strain in a ring on its mechanical properties in subsequent elongation

摘要

The mechanical properties of containment pipes used in the active zones of nuclear reactors can be estimated by subjecting rings to circumferential tension on semicylindrical supports. The problem lies with evaluating the plastic properties of the shell material from its load-elongation curve. As the test begins, the ring ovalizes, and this makes any attempt to estimate the mechanical properties prone to error. The goal hereof is to find where the strain pertaining to such ovalization is inhomogeneous and to analyze how such inhomogeneity can affect the determination of mechanical properties. In order to reveal the effect of strain uncontrollable by standard procedures, rings and ovalized specimens marked on their end faces were tested. The experiments found that, in testing ring-shaped specimens, inhomogeneous strain segments were associated with a higher statistical error in the determination of mechanical properties as compared to testing ovalized specimens. Tensile testing of the ovalized specimens yielded a more accurate assessment of the plastic properties of the material.