Study of Fatigue Properties of Graphite Materials Under Four-Point Bending

Abstract The structural integrity of graphite components, supporting the reactor core of HTGRs (High-Temperature Gas-Cooled Reactor), is essential to the operational safety of the reactor. Therefore, the fatigue performance of graphite structures has been an extremely significant issue in both academia and industry. Currently, the stress amplitudes of the fatigue tests of nuclear graphite are normally less than its tensile strength, which is unsuitable for some components with stress concentrations. In this paper, fatigue tests with four-point bending loading were carried out to investigate the fatigue behavior of the nuclear-grade graphite material IG110 at stress levels higher than tensile strength. The four-point bending fatigue test fixture was designed based on the ASTM test standard. Different samples were tested to study the stress concentration effects. In the test, the bending fatigue life of graphite materials under different stress levels was obtained. The fatigue properties of graphite materials under bending load were also analyzed. This study not only provides important experimental data and theoretical guidance for the engineering application of nuclear-grade graphite materials in HTGRs, but also provides useful experience and inspiration for the fatigue performance studies of other brittle materials.