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.

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.

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.

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.

Diffusion and Mixing in Microchannel Analyzed by the Luminol Chemiluminescence

2013 ◽  
Author(s):  
Ruru Matsuo ◽  
Ryosuke Matsumoto
Keyword(s):  
Numerical Simulation ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Mixing Layer ◽  
Fluorescence Technique ◽  
Chemiluminescence Intensity ◽  
Luminol Chemiluminescence ◽  
Chemical Reaction Rate ◽  
Pdms Chip ◽  
Reaction Profile

This study focused on the diffusion and mixing phenomena investigated by using luminol chemiluminescence (CL) to estimate the local chemical reaction rate in the T-junction microchannel. Generally, the degree of mixing in microchannel is calculated by the deviation of the obtained concentration profiles from the uniform concentration profile by using fluorescence technique. Thus, the degree of mixing is a macroscopic estimate for the whole microchannel, which is inappropriate for understanding the diffusion and mixing phenomena in the mixing layer. In this study, the luminol CL reaction is applied to visualize the local chemical reaction and to estimate the local diffusion and mixing phenomena at an interface between two liquids in microchannel. Luminol emits blue chemiluminescence when it reacts with the hydrogen peroxide at the mixing layer. Experiments were carried out on the T-junction microchannel with 200 microns in width and 50 microns in depth casted in the PDMS chip. The chemiluminescence intensity profiles clearly show the mixing layer at an interface between two liquids. The experimental results are compared with the results of numerical simulation that involves solving the mass transport equations including the chemical reaction term. By calibrating CL intensity to the chemical reaction rate estimated by the numerical simulation, the local chemical reaction profile can be quantitatively estimated from the CL intensity profile.

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