Creep and recovery in graphites at ambient temperature: An acoustic emission study

• Published in: Carbon (New York) Vol. 32; no. 4; pp. 553 - 558
• Main Authors: Neighbour, Gareth B., McEnaney, Brian
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 1994; Elsevier Science
• Subjects: acoustic emission; Condensed matter: structure, mechanical and thermal properties; Creep; Exact sciences and technology; Graphite; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Physics; acoustic emission; creep; Graphite; Compressive stress; Tensile stress; Creep; Recovery(properties); Acoustic emission; Experimental study
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/0008-6223(94)90071-X

Nuclear graphites subject to compressive or tensile stress cycling show a Felicity effect, that is, acoustic emission (AE) is detected at stresses less than the previous peak stress. This is attributed to recovery processes that occur upon unloading and at zero stress. The extent of recovery increases with time (up to 10 5 mins) at zero stress between cycles. For two graphites (IM1-24 and PGA) held under constant compressive or tensile strain, AE over ∼16 h is attributed to creep. For the same graphites at zero stress (after application of a compressive or tensile prestress), AE over ∼16 h is attributed to creep recovery. Both types of AE time curve follow logarithmic rate laws similar to those derived earlier for high-temperature primary creep and creep recovery. The micromechanical processes that give rise to creep and AE on loading graphites are basal plane shear and microcracking; creep recovery is attributed to the reverse of these processes.