Brittle deformation, brittle–plastic and brittle–ductile transition

Abstract

Non-elastic deformation is conveniently classified into brittle and plastic (ductile) deformation based on the scale of discontinuous deformation. Although the main focus of this book is plastic (ductile) deformation, some knowledge of brittle deformation is critical to the understanding of rheological stratification of the lithosphere. Also an understanding of brittle to plastic transition is essential for the understanding of the origin of deep and intermediate earthquakes. This chapter provides a brief summary of brittle deformation and the major differences between brittle and plastic deformation. The nature of brittle–plastic transition is discussed based on the different dependence of strength in two regimes on temperature and pressure and other parameters. Key words micro-cracks, faulting, Coulomb–Navier's law, Byerlee's law, pore fluid pressure, brittle fracture, plastic flow, brittle–ductile transition, semi-brittle deformation, brittle–plastic transition. Brittle fracture and plastic flow a general introduction When a stress is applied to a material, a material will deform elastically when the stress is small or when stress is applied at low temperatures (or for a short time). Deformation of a material in this case is due to a small displacement of atoms from their stable positions. Upon applying stress, atoms move to new equilibrium positions instantaneously, and upon the removal of this stress, they move back to their original positions. The nature of elastic deformation and the elastic properties of materials are discussed in Chapter 4.