Relation between static and dynamic Young's modulus of nuclear graphites and carbon

Abstract

In order to evaluate precisely the stresses and strains generated in the graphite structures of high temperature gas-cooled reactors (HTGRs), it is necessary to use not only correct stress-strain relationships but also proper values of the Young's modulus of HTGR graphites. In this study the relation between the Young's modulus obtained from the slope of the stress-strain curve at the origin and that measured by the ultrasonic wave propagation method was examined on two grades of HTGR graphites (IG-110 and PGX) and a grade of carbon materials (ASR-ORB). One of the main conclusions obtained here is that the ratio of the static Young's modulus to the dynamic one depends upon the accuracy of the strain measurement. If the Young's modulus which is evaluated from the secant at 0.01 to 0.05% strain is taken as the static modulus, the dynamic Young's modulus measured using a 5-MHz transducer is approximately equal to the static one.