Computer Simulation of Defect Properties and Processes at High Temperature

1985 ◽  
Vol 60 ◽  
Author(s):  
J. H. Harding
Keyword(s):  
Computer Simulation ◽  
High Temperature ◽  
Point Defects ◽  
Reaction Rate ◽  
Rate Theory ◽  
Reaction Rate Theory ◽  
Lattice Calculations ◽  
And Migration ◽  
Static Lattice

AbstractWe show how the entropies of formation and migration of point defects may be calculated accurately. The approximations inherent within static lattice calculations are assessed, in particular the Vineyard reaction rate theory.

A Kinetic Model of Precipitate Evolution

1995 ◽  
Vol 398 ◽  
Author(s):  
C. Lane Rohrer ◽  
M. D. Asta ◽  
S. M. Foiles ◽  
R. W. Hyland
Keyword(s):  
Point Defects ◽  
Reaction Rate ◽  
Al Alloys ◽  
Computational Method ◽  
Rate Theory ◽  
Homogeneous Precipitation ◽  
Temperature Dependent ◽  
Reaction Rate Theory ◽  
Chemical Reaction Rate ◽  
Kinetics Of

ABSTRACTChemical reaction rate theory is used to model the kinetics of precipitation reactions in Al alloys, including the effects of continuous cooling and thermally generated point defects. The computational method models the processes of nucleation, growth, and coarsening within a single framework. Calculated time and temperature dependent precipitate number densities and sizes during the homogeneous precipitation of the A13Sc phase in an Al-.11 at% Sc alloy are shown to compare favorably with experimental observations.

Thermal Decomposition Kinetics of Glyphosate (GP) and its Metabolite Aminomethylphosphonic Acid (AMPA)

2019 ◽  
Author(s):  
Milad Narimani ◽  
Gabriel da Silva
Keyword(s):  
Thermal Decomposition ◽  
Reaction Rate ◽  
Decomposition Kinetics ◽  
Rate Theory ◽  
Thermal Decomposition Mechanism ◽  
Treatment Processes ◽  
Aminomethylphosphonic Acid ◽  
Reaction Rate Theory ◽  
Decomposition Chemistry ◽  
Kinetics Of

Glyphosate (GP) is a widely used herbicide worldwide, yet accumulation of GP and its main byproduct, aminomethylphosphonic acid (AMPA), in soil and water has raised concerns about its potential effects to human health. Thermal treatment processes are one option for decontaminating material containing GP and AMPA, yet the thermal decomposition chemistry of these compounds remains poorly understood. Here, we have revealed the thermal decomposition mechanism of GP and AMPA by applying computational chemistry and reaction rate theory methods. <br>

Ab Initio Computation of Thermochemistry and Kinetics in the Oxidation of Gas Phase Silicon Species

1992 ◽  
Vol 282 ◽  
Author(s):  
Michael R. Zachariah ◽  
Wing Tsang
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Energy Barrier ◽  
Reaction Rate ◽  
Rate Theory ◽  
Molecular Orbital Calculations ◽  
Activation Energy Barrier ◽  
Ab Initio Computation ◽  
Oxygen Donor ◽  
Reaction Rate Theory

ABSTRACTAb initio molecular orbital calculations coupled to RRKM reaction rate theory have been conducted on some important reactions involved in the oxidation of silane in a high-temperature/high H2O environment. The results indicate thatH2O acts as an oxygen donor to SiH2 to form H3SiOH or SiH2O. Subsequent reactions involve the formation of (HSiOOH, H2Si(OH)2,:Si(OH)2 or SiO). In turn SiO polymerizes into planar rings, without an activation energy barrier. A list of calculated thermochemical data are also presented for a number of equilibrium species.

scholarly journals A Unified Constitutive Model for Creep and Cyclic Viscoplasticity Behavior Simulation of Steels Based on the Absolute Reaction Rate Theory

2017 ◽  
Vol 2017 ◽  
pp. 1-13
Author(s):  
Huayan Chen ◽  
Xiangguo Zeng ◽  
Yang Guo ◽  
Fang Wang
Keyword(s):  
Constitutive Model ◽  
Reaction Rate ◽  
Internal State ◽  
Rate Theory ◽  
State Variables ◽  
Absolute Reaction Rate Theory ◽  
Reaction Rate Theory ◽  
Absolute Reaction Rate ◽  
The Absolute ◽  
Absolute Reaction

In this work, the viscoplasticity and creep behavior for modified 9Cr-1Mo and 316 stainless steels were investigated. Based on the absolute reaction rate theory, a unified constitutive model incorporating internal state variables was proposed to characterize the evolution of the back stress. Also, the model was implemented by the ABAQUS system with the semi-implicit stress integration. Compared to the experimental data, the results demonstrated that the proposed approach could effectively simulate the cyclic softening and hardening behavior for such structural steels.

A Mechanical Equation of State for Inelastic Deformation of Iron: An Analytic Description

1977 ◽  
Vol 99 (1) ◽  
pp. 59-64 ◽  
Author(s):  
R. W. Rohde ◽  
J. C. Swearengen
Keyword(s):  
Equation Of State ◽  
Stress Relaxation ◽  
Power Law ◽  
Reaction Rate ◽  
Equations Of State ◽  
Analytic Description ◽  
Rate Theory ◽  
Predictive Capability ◽  
Reaction Rate Theory ◽  
The Relationship

The applicability of two familiar analytic descriptions of micromechanical deformation as equations of state for polycrystalline iron is discussed. These equations are the power law and the relationship based on reaction rate theory. It is shown that the reaction rate description fails to describe adequately individual stress relaxation events without invoking undue complexity from use of adjustable parameters. Moreover, even in that case, this formulation lacks the predictive capability required in an equation of state. Conversely, the power law is found not only to describe stress relaxation data properly but also to provide the capability of predicting stress relaxation following initial deformation by different loading paths. It thus appears to represent an equation of state for the material.

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