MECHANICAL PROPERTIES OF EGCR-TYPE AGOT GRAPHITE

Mechanical properties of a coarse-grained nuclear graphite, designated EGCR-type AGOT, obtained from tests at room temperature, 1000, 2000 and 4500°F are given. The main emphasis of the paper is, however, on room temperature results; these include stress and lateral strain vs. longitudinal strain curves. Size effect and stress gradient influences upon the material behavior were studied, and two important conclusions reached. These are 1. (1) size effects, including volume and cross-sectional area, are small or nonexistent within the size range investigated, and 2. (2) the behavior is the same in flexural and in uniaxial tests. Numerous specimens of each type were tested at room temperature, and the data obtained are treated on a statistical basis to give mean curves for comparison purposes. In addition, the statistical approach used here provides results which can be taken as characteristic of a single piece of material tested in different ways. This is very important because these results provide a basis for the development of constitutive equations applicable to combined states of stress. The room-temperature data are examined in terms of elastic-plastic behavior, and it is shown that an equation derived by Jenkins gives good fits (within limits) to the stress-strain curves. Lateral-to-longitudinal strain ratio vs. longitudinal strain data, which are given here, are decomposed into elastic strain ratio, or Poisson ratio, and plastic strain ratio components. The Poisson ratios are essentially the same in tension and in compression. It is shown that the plastic strain ratios tend to remain constant with increased longitudinal strain in compression, while these ratios tend to decrease with longitudinal strain in tension. © 1969.