The Activation Energy for Plastic Flow in Spatially Extended Polycrystalline Systems during Tension Test

2008 ◽  
Vol 1 (S1) ◽  
pp. 81-84 ◽  
Author(s):  
J. D. Muñoz-Andrade
Keyword(s):  
Activation Energy ◽  
Plastic Flow ◽  
Tension Test ◽  
Spatially Extended

scholarly journals PLASTIC DEFORMATION OF THICK-WALLED SNOW-ICE CYLINDERS UNDER HYDROSTATIC PRESSURE

1962 ◽  
Vol 40 (10) ◽  
pp. 1310-1318 ◽  
Author(s):  
H. H. G. Jellinek
Keyword(s):  
Activation Energy ◽  
Plastic Deformation ◽  
Hydrostatic Pressure ◽  
Strain Rate ◽  
Plastic Flow ◽  
Constant Pressure ◽  
Circumferential Stress ◽  
Sine Function ◽  
Kcal Mole ◽  
Flow Process

The results of experiments on the plastic deformation of hollow snow-ice cylinders, closed at one end, as a function of circumferential stress and temperature are discussed. Data are graphed on deformation as a function of time for a snow-ice cylinder under 7.03 and 14.06 kg/cm2 hydrostatic pressure at −4.5 °C, deformation as a function of hydrostatic pressure from 2.11 to 7.03 kg/cm2, and deformation as a function of temperature at a constant pressure of 10.55 kg/cm2. The natural strain rate of closure at constant circumferential stress and temperature was a constant, which varied with circumferential stress as a sine function and was "exponentially dependent on temperature, with an activation energy of 14.1 kcal/mole at an average circumferential stress of 3.1 kg/cm2. The experiments agree well with an earlier interpretation of the plastic flow process representing flow between grain boundaries.

Annealing of pressure-induced structural damage in superconducting Bi–Pb–Sr–Ca–Cu–O ceramic

1993 ◽  
Vol 8 (9) ◽  
pp. 2177-2186 ◽  
Author(s):  
I. Maartense ◽  
Asok K. Sarkar
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Transition Temperature ◽  
Residual Stresses ◽  
Plastic Flow ◽  
Structural Damage ◽  
Ac Susceptibility ◽  
Sample Volume ◽  
Effective Grain Size ◽  
Small Improvement

Ac susceptibility measurements have been used to monitor the changes in the superconductive properties of sintered and uniaxially pressed samples of Pb-stabilized 2223-phase bismuth cuprate ceramic as the structural damage was annealed in air in a sequence of steps in temperature between 500 and 850 °C. It is concluded that below 600 °C a relaxation of residual stresses is responsible for a 2% shrinkage in sample volume and a small improvement in bulk superconductive transition temperature, Tc. Above 700 °C, a recovery of the original properties occurs through grain regrowth governed by an activation energy of ∼200 kJ/mol. However, in the region between 600 and 700 °C, a decrease in Tc of ∼40 K appears to be the result of plastic flow and amorphization associated with local decomposition of 2223 which reduces the effective grain size and weakens the intergranular superconductive coupling.

Influence of Grain Size and Thermo-Mechanical Conditions on the Activation Energy for Super Plastic Flow in Ti-6Al-4V Alloy

2018 ◽  
Vol 941 ◽  
pp. 1210-1215
Author(s):  
Juan Daniel Muñoz-Andrade
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Grain Boundary ◽  
Plastic Flow ◽  
Power Dissipation ◽  
Direct Determination ◽  
Grain Boundary Sliding ◽  
Advanced Materials ◽  
Super Plastic ◽  
Boundary Sliding

The essential objective of this work is to establish the influence of grain size and thermo-mechanical conditions on the activation energy for super plastic flow (QSPF) in Ti-6Al-4V alloy by applying the quantum mechanics and relativistic model (QM-RM) proposed by Muñoz-Andrade, in the framework of the unified physics. The QM-RM allows the direct determination of the QSPF in advanced materials at instantaneous thermo-mechanical material working conditions. By applying, the QM-RM on the experimental results reported previously by some authors, it is shown for grain size of 6.1μm, that the calculated QSPF for grain boundary sliding is about 193 and 178 kJ/mol, at 850°C with an efficiency of power dissipation, η=0.65. These results are in closed agreement with the values of 204 and 174 kJ/mol reported previously for grain boundary self-diffusion energy of α-Ti. Nevertheless, for grain size of 0.6μm the calculated QSPF is 142 kJ/mol at 650°C, with an efficiency of power dissipation, η=0.61. As well, in order to understand the phenomenology and mechanics of SPF in Ti-6Al-4V alloy, the variation of the activation energy with the temperature; stress and strain rate is analyzed in association with coupled mechanisms during SPF, such as grain boundary sliding, cooperative grain boundary sliding and self-accommodation process related to the microstructure. In summary, the results of QSPF obtained in this work, by the QM-RM are in closed agreement with results reported previously by using the theoretical and conventional methodology set up by Mohamed and Langdon.

Mapping of the Granular Flow during the Irreversible Deformation Processes in Spatially Extended Polycrystalline Systems

2007 ◽  
Vol 561-565 ◽  
pp. 901-904 ◽  
Author(s):  
Juan Daniel Muñoz-Andrade
Keyword(s):  
Plastic Flow ◽  
Granular Flow ◽  
Irreversible Deformation ◽  
Dislocation Dynamics ◽  
Hyperbolic Motion ◽  
Spatially Extended ◽  
Super Plastic ◽  
Deformation Processes ◽  
Recession Velocity ◽  
Hubble Flow

The objective of this work is to obtain the mapping of the granular flow during the irreversible deformation processes in spatially extended polycrystalline systems (SEPCS) in order to describe and analyse the phenomenology and mechanics of the granular flow. In general, it was established for commercial alloys that, the granular flow is linked with the hyperbolic motion due to dislocation dynamics and self accommodation of grains. Also, the recession velocity of grains in the stain field on the surface of SEPCS increased with the distance along the tension axis from the origin of the coordinate system of reference. This behaviour is very similar to the Hubble flow associated with the expansion process of the universe, where the recession velocity of the galaxies increased in a linear relationship with their distance. In this physical framework the main results are analysed in the context of the unified interpretation of the Hubble flow, plastic flow and super plastic flow [1-6].

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