A Reaction-Rate Treatment of the Life Fraction Hypothesis in Creep Testing

1969 ◽  
Vol 91 (1) ◽  
pp. 56-58 ◽  
Author(s):  
M. Grounes
Keyword(s):  
Reaction Rate ◽  
Generalized Equation ◽  
Rate Theory ◽  
Creep Data ◽  
Empirical Parameter ◽  
Design Considerations ◽  
Reaction Rate Theory ◽  
Life Fraction ◽  
Selection Of ◽  
Made In

The equation describing Robinson’s life fraction hypothesis has been derived from a generalized equation based on chemical reaction-rate theory. It is shown what further assumptions are needed in order to make this hypothesis valid. For design considerations the following equation is suggested ∑j=1mtjtaj≤k where tj = time spent at Tj, σj; taj = time needed to rupture, etc., at Tj, σj; k = empirical parameter, smaller than 1. The selection of a numerical value for k is based on an analysis of how conventional creep data comply with various assumptions made in the derivation of the equation; T = temperature; and σ = stress.

A Reaction-Rate Treatment of the Extrapolation Methods in Creep Testing

1969 ◽  
Vol 91 (1) ◽  
pp. 59-62 ◽  
Author(s):  
M. Grounes
Keyword(s):  
Creep Rate ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Generalized Equation ◽  
Rate Theory ◽  
Extrapolation Methods ◽  
Time To Rupture ◽  
Reaction Rate Theory ◽  
Phenomenological Equations ◽  
Chemical Reaction Rate

Various phenomenological equations for the dependence of the time-to-rupture, etc., on temperature and stress have been related to a generalized equation based on chemical reaction-rate theory. In the derivation of these equations the assumption, which has been used and criticized in earlier work, that the time-to-rupture is inversely proportional to the creep rate and thus that the ductility is constant, is not needed.

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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