Compressive stress-strain relationships for nuclear graphites

Compressine stress-strain relationships for nine commercial graphite materials produced by four various methods, extrusion, molding, vibration molding, and isostatic press, were systematically studied, Polynomial expressions for stress-strain curves of the graphites were proposed all over strains to the fractures. The effects of anisotropy induced by alignment of grains on stress-strain curves and the effects of applied stress on plastic strains were also examined. The flow stress of the with-grain specimen were larger than that of across-grain specimen at small strain (<1%). The effects of compressive stress on Young's modulus were examined using ultrasonic wave velocity. The Young's modulus of the graphites decreased successively with increasing applied stress. The origin of the phenomenon was attributable to the change in pore configuration under compressive stress. (author)