The effect of compressive prestressing on the mechanical properties of some nuclear graphites

Abstract

The effects of prestressing in compression at room temperature on the Young's modulus, the tensile strength, and the compressive strength of some nuclear graphites were examined. Also the effects of strain rate in the range of 10 −5 ~ 10 −2 sec −1 on the room temperature tensile and compressive strengths were investigated. The Young's modulus and the tensile strength of the graphites decreased as the compressive prestress increased above a particular prestress level. However, the compressive strength of the graphites did not change appreciably for the above range of strain rates. The decrease in Young's modulus and tensile strength with increasing prestress is considered to be due to two factors: an increase in the dislocation density and an increase in the size and number of cracks produced. It is inferred that the decrease in the strength at higher prestress levels is due to the formation and propagation of cracks with increasing prestress, since some growth of cracks was observed in the higher prestressed graphites.