Deformation fractures

Hertzberg, R. W., Deformation Fracture Mechanics of Engineering Materials, Wiley, 1976. 

Osteogenesis imperfecta Mutations in collagen genes Skeletal deformities Fractures, blue sclera... 

The purpose of this paper is to investigate the mechanical properties (plastic deformation, micromechanisms of deformation, fracture) of several amorphous polymers considered in [1], i.e. poly(methyl methacrylate) and its maleimide and glutarimide copolymers, bisphenol A polycarbonate, aryl-aliphatic copolyamides. Then to analyse, in each polymer series, the effect of chemical structure on mechanical properties and, finally, to relate the latter to the motions involved in the secondary transitions identified in [ 1] (in most cases, the p transition). 

The goal of this investigation of the mechanical properties of amorphous polymers (plastic deformation, micromechanisms of deformation, fracture) was to analyse the influence of secondary transition motions on these properties. 

Besides deformation, fracture is the other response of materials to a stress. Fracture is the stress-induced breakup of a material. Two types of fracture are commonly defined. A brittle fracture is breakup which occurs abruptly without localized reduction in area. A ductile fracture is the failure of the material which is preceded by appreciable plastic deformation and localized reduction in area (necked region). The brittle fracture and ductile fracture are schematically illustrated in Fig. 1.10. 

In this chapter, we first briefly describe some of the apparatus used in FE studies. Then we discuss some of the FE observations which have been made during the various stages of deformation, fracture, and relaxation to equilibrium, with emphasis on the processes believed to be responsible for the emissions. Finally, we list some of the potential applications and implications of this work. 

S5 Strongly shocked Strong mosaicism, planar fractures, planar deformation fractures Maskelynite 45-55... 

Dowling, N. E., Mechanical Behavior of Materials Engineering Methods for Deformation, Fracture and Fatigue, 2nd ed, Prentice Hall, Inc., Upper Saddle River, NJ (1999). 

Abstract This paper presents a model for the simulation of two phase flow phenomena in deformable fractured rocks. The main problem is that gas pressure may play an important role on the mechanical behavior specially if discontinuities exist or develop. Fracture aperture changes and fracture failure are accounted by the model. Aperture of the discontinuity is used as the main variable for permeability and capillary pressure variations. Injection pressures that show peak values before steady state regime is attained are obtained with the model as shown in some simulations performed. 

Abstract This contribution deals with the modeling of coupled thermal (T), hydraulic (H) and mechanical (M) processes in subsurface structures or barrier systems. We assume a system of three phases a deformable fractured porous medium fully or partially saturated with liquid and a gas which remains at atmospheric pressure. Consideration of the thermal flow problem leads to an extensively coupled problem consisting of an elliptic and parabolic-hyperbolic set of partial differential equations. The resulting initial boundary value problems are outlined. Their finite element representation and the required solving algorithms and control options for the coupled processes are implemented using object-oriented programming in the finite element code RockFlow/RockMech. 

Abstract motif is a three-dimensional finite-element code developed to simulate groundwater flow, heat transfer and solute transport in deformable fractured porous media. The code has been subjected to an extensive verification and updating programme since the onset of its development. In this paper, additional verification and validation works with an emphasis on thermo-hydro-mechanical processes are presented. The verification results are based on cases designed to verify thermo-hydro-mechanical coupling terms, and isothermal and non-isothermal consolidations. A number of validation case studies have been conducted on the code. Example results are repotted in this paper. 

The MOTIF code is a three-dimensional finite-element code capable of simulating steady state or transient coupled/uncoupled variable-density, variable- saturation fluid flow, heat transport, and conservative or nonspecies radionuclide) transport in deformable fractured/ porous media. In the code, the porous medium component is represented by hexahedral elements, triangular prism elements, tetrahedral elements, quadrilateral planar elements, and lineal elements. Discrete fractures are represented by biplanar quadrilateral elements (for the equilibrium equation), and monoplanar quadrilateral elements (for flow and transport equations). 

Chan, T., Reid, J.A.K. and Guvanasen, V. 1987. Numerical modelling of coupled fluid, heat, and solute transport in deformable fractured rock. In Coupled Processes Associated with Nuclear Waste... 

Bai, M. and Roegiers, J.C. 1994. Fluid flow and heat flow in deformable fractured porous media. Int. J. Engng Sci. 32(10) pp. 1615-1633. Callari C. Federico F. 2000. FEM validation of a double porosity elastic model for consolidation of structurally complex clayey soils. Int. J. Numer. Analy. Meth. 24 (4) pp. 367-402. 

Deformation, fracture and stress relaxation at high temperatures in many respects are similar to these phenomena at low temperatures. The major distinction between fracture at high and low temperatures lies in the fact that at high temperature the direction of crack propagation occurs at the angle 90° to the nanotube axis. As a result, the fracture surface has numerous steps. At the macroscopic level it corresponds to tough fracture. 

Simultaneously, processes of plastic deformation, fracture and interactions with the environment, and counterbody can occur. The latter ones have been studied by mechanical engineers and tribologists, but the processes of phase transformations at the sharp contact have been investigated for only a few materials (primarily, semiconductors) and the data obtained so far can only be considered preliminary. One of the reasons for the lack of information may be the fact that the problem is at the interface between at least three scientific fields, that is, materials science, mechanics, and solid state physics. Thus, an interdisciplinary approach is required to solve this problem and understand how and why a nonhydrostatic (shear) stress in the two-body contact can drive phase transformations in materials. 

Lake, G.J., 1970. In Proceedings of International Conference on Yield Deformation Fracture Polymers, Cambridge. Institute of Physics, London, p. 53. 

BS mm physical crack length augmented to account for crack tip plastic deformation (fracture mirror length)... 

The concept that kinetics of deformation, relaxation, and fracture are based on thermal fluctuations presents alternative interpretation of the physical nature of the activation parameters. In the proposed approach, the Uq and y parameters are characteristics of a complicated, multistage process. It consists of generation of the exdted chemical bonds, their relaxation, generation of the elementary nuclei of deformation/fracture, their coalescence, and macroscopic defoimation/fracture. 

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