Chemical Kinetics of Plastic Deformation

Krausz, A. S.; Eyring, Henry

doi:10.1063/1.1660552

Cited by 34 publications

(7 citation statements)

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“…Using chemical kinetics and deformation kinetics concepts [5] the theory of consecutive bond breaking processes associated with steady state plastic flow was formulated by Krausz and Eyring [6]. Using chemical kinetics and deformation kinetics concepts [5] the theory of consecutive bond breaking processes associated with steady state plastic flow was formulated by Krausz and Eyring [6].…”

Section: Discussionmentioning

confidence: 99%

The theory of non-steady state fracture propagation rate

Krausz

1976

Int J Fract

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A B S T R A C T The classical concepts of the Tobolsky~Eyring theory of thermally activated bond breaking and mending mechanism were extended to describe fracture propagation at the molecular level. The analysis shows that the physical process which controls the propagation rate of cracks is described by a differential equation identical to the mathematical representation of the counterpart problems in heat transfer and diffusion.

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Section: Discussionmentioning

confidence: 99%

The theory of non-steady state fracture propagation rate

Krausz

1976

Int J Fract

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“…Following the theory of absolute reaction rates, Becker [21] first supposed and showed that thermal fluctuations can promote slip in crystals and, at high temperatures, decrease shear stresses necessary for slip. Startsev et al [22], Krausz and Eyring [23] have confirmed that one can consider an elementary act of plastic deformation, displacement of a dislocation, in a crystal as an atomic rearrangement in a peculiar gigantic molecule. In fact, this process is equivalent to a special chemical reaction.…”

Section: Determination Of the Critical Temperaturementioning

confidence: 85%

“…where AF is the change of the Gibbs free energy of activation (thermodynamic potential), A U is the activation enthalpy (energy), AS is the entropy change, iz~l is a structure factor, which, according to Gibbs [23], involves the density of movable dislocations and geometric characteristics, and exp (AS~r) is the entropy term, appearing in the equations including the activation enthalpy (energy) U and a preexponential multiplier E~l. Equation (3) is considered valid for the rate of plastic deformation under constant stress ( ~ = const) at the prescribed stage of creep and active deformation.…”

Section: Determination Of the Critical Temperaturementioning

confidence: 99%

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Simulation of temperature flashes with regard for the physicomechanical properties of metals

Shyrokov¹,

Koval'chyk²

1998

Mater Sci

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We present and analyze theoretical approaches to simulation of temperature flashes. A developed mathematical model enables us to calculate the maximum temperature of a friction surface. A new criterion for choice of the critical temperature of wear of a single microasperity is physically grounded.Experimental data on friction at macro-and microlevels are sometimes mutually contradictory, since friction is a dynamical totality of various processes : physical, mechanical, chemical, etc. ones [1-3]. In many cases, measurements at the microlevel are very difficult to perform and sometimes impossible. For example, the distribution and migration of real contact spots along the nominal friction surface are unknown [4,5]. In view of both the very small sizes of those spots and the almost instantaneous time of their existence in the range 10 -3-10 -6 sec, researchers do not carry out experiments for determination of temperature flashes [5] on an actual contact spot. Therefore, it is theoretical approaches that take a special place in tribology.One of the most important directions of the development of tribology is thermophysics and the heat dynamics of friction and wear. In this field, in our opinion, the most profound development and comprehensive analysis were carded out by Chichinadze and his followers [ 1,[5][6][7][8]. They considered three kinds of temperatures: contact, bulk, and flash temperatures [5]. Contact temperature is broadly used for various estimates of the behavior of a friction process, whereas the need to know the distribution of bulk temperature is, in the first place, connected with the specific character of the work of brakes [5][6][7].Study of so-called temperature flashes and, in particular, determination of their absolute value [1, 5] form a separate subsection of the heat dynamics of friction. One of the founders of the concept of temperature flashes, Blok [9], believed that they arise as a result of breakage of molecular bonds on actual contact spots and exceed surface temperatures. Such flashes determine the maximum temperature of contact points of microasperities on the surfaces of fricting bodies. Since it is impossible to experimentally estimate migration and the distribution of contact spots, their temperature can be found only theoretically. Below, we consider the existing approaches to the simulation of temperature flashes. Chichinadze ModelThe maximum temperature on an actual contact spot is represented as a sum [1,5] Tma x = T 1 + T 2, where T 1 is the integral average temperature of the nominal or contour surface of friction which appears due to a heat flow uniformly distributed along it, and T 2 is the temperature flash giving the extra temperature with respect to T I on the actual contact spot.Consider a scheme of the motion of a microasperity l along a smooth half space 2. We assume that the average contact spot is so small that the surface along which it moves is infinite. Moreover, we assume that the contact spot is formed as a result of the interaction between a single microasper...

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“…Based on the Arrhenius-equation, Krausz and Eyring [58] described the plastic deformation using the kinetics of chemical reactions, ̇ , where ̇ is the strain rate during plastic deformation, is Burgers vector in terms the magnitude of dislocation movement of atoms, is dislocation density and is dislocation velocity. According to this description, they derived a temperature-dependent rate constant, , to describe the strain rate in a plastic deformation area:…”

Section: The Arrhenius-type Equation and Rate Controlling Theorymentioning

confidence: 99%

Temperature-Dependent Fracture Toughness Evaluation of WC-10Co4Cr Coating/1018 Low Carbon Steel Substrate System

Gu¹

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The temperature-dependent fracture toughness of WC-10Co4Cr coating/1018 low carbon steel substrate, which is a brittle coating/ductile substrate system, is evaluated at microscopic level with two types of models developed in terms of the Arrhenius-type equation and rate controlling theory, utilizing indentation test data, in this research. One is based on the crystal structures of individual phases in the composite coating, the other considers the microcrack formation in the coating/substrate system under indentation loading. Using the crystal-structure-based model, the slip systems of the hard hexagonal -WC phase and soft FCC -Co phase are analyzed. The fracture toughness of the two-phase composite coating is obtained by integrating the fracture toughness of -WC phase and -Co phase using either the basic mixture method or the unconstrained mixture method. The estimated fracture toughness using this type of model is independent of indentation load. For the microcrack-formation-based models, numerous microcracks are generated from each corner of indentation impression and merge together to form radial cracks due to the tension of residual stresses in the coating/substrate system under indentation, and the radial cracks extend along the indentation diagonals under the residual stresses. The dislocation movement of atoms can be associated with the microcrack formation in the indentation process thus the fracture toughness of the composite coating/substrate system is evaluated. Due to the effect of ductile substrate on brittle coating, two approaches are used to investigate the indentation pressure imposed on the system, one expresses the indentation pressure as the applied load ii divided by the projected area of indentation impression, the other is based on the composite hardness of the coating/substrate system, but both approaches take the substrate effect into the fracture toughness evaluation. The estimated fracture toughness of WC-10Co4Cr coating/1018 low carbon steel substrate system at high temperatures shows that the crystal-structure-based model and microcrack-formation-based models are in good agreement. The fracture toughness of WC-10Co4Cr coating/1018 low carbon steel substrate system remains unchanged until the temperature reaches a critical value, 200 for crystal-structure-based model, 150 for microcrack-formation-based models. It then increases rapidly in an exponential manner. The room-temperature fracture toughness of the coating/substrate system obtained from all models is about 2.1 ⁄ , the fracture toughness at 1000 ranges from 8.5669 ⁄ to 11.2399 ⁄ using different models and under different indentation loads. iii Acknowledgements I owe my sincere gratitude to my supervisors, Professor Rong Liu, for her constant support and guidance during my research and study at Carleton University. Her expert knowledge and endless patience are invaluable and indispensible for me to finish this thesis.

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Chemical Kinetics of Plastic Deformation

Cited by 34 publications

References 5 publications

The theory of non-steady state fracture propagation rate

The theory of non-steady state fracture propagation rate

Simulation of temperature flashes with regard for the physicomechanical properties of metals

Temperature-Dependent Fracture Toughness Evaluation of WC-10Co4Cr Coating/1018 Low Carbon Steel Substrate System

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