ACTIVATION ENERGY FOR CREEP OF TIN

1958 ◽  
Vol 36 (11) ◽  
pp. 1445-1449 ◽  
Author(s):  
L. G. Bonar ◽  
G. B. Craig
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
High Purity ◽  
Steady State Creep ◽  
Temperature Cycling ◽  
Constant Stress ◽  
Creep Tests ◽  
Temperature Range ◽  
A Value

The literature reports values ranging from 8000 to 26,000 cal per g-atom for the activation energy for the creep of tin. The present investigation analyzed the results of constant stress creep tests during steady state creep, and by means of temperature cycling. A value of approximately 9000 cal per g-atom for the creep of high purity tin in the temperature range 300 to 350° K was obtained.

New Description of Steady-State Creep Rate, Yield Stress, Stress Relaxation and Their Interrelation

2005 ◽  
Vol 482 ◽  
pp. 319-322
Author(s):  
Jan Kohout
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Creep Rate ◽  
Yield Stress ◽  
Applied Stress ◽  
Stress Sensitivity ◽  
Steady State Creep ◽  
Steady State Creep Rate ◽  
Creep Tests ◽  
Sensitivity Parameter

The steady-state creep rate increases with temperature according to the Arrhenius equation and its increase with applied stress is mostly described by the power law. Combining both these laws, equation ) exp( RT Qa n − µ s e& is obtained, where apparent activation energy a Q and stress sensitivity parameter n are considered to be constants. But most measurements show some dependence of activation energy on applied stress and of stress sensitivity parameter on temperature. An equation respecting these facts is derived in the paper and verified using some published results of creep tests. Based on this derived equation, the dependence of yield stress on temperature and strain rate and an equation describing the relaxation curves are deduced.

Kinetics of the hydrolysis of cellobiose and p-nitrophenyl-β-D-glucoside by cellobiase of Trichoderma viride

1977 ◽  
Vol 55 (1) ◽  
pp. 19-26 ◽  
Author(s):  
R. James Maguire
Keyword(s):  
Steady State ◽  
Trichoderma Viride ◽  
Solution Temperature ◽  
Temperature Range ◽  
A Value ◽  
Steady State Kinetics ◽  
Decreasing Ph ◽  
Ph Curve ◽  
Kinetics Of ◽  
Hydrolysis Of

Cellobiase has been isolated from the crude cellulase mixture of enzymes of Trichoderma viride using column chromatographic and ion-exchange methods. The steady-state kinetics of the hydrolysis of cellobiose have been investigated as a function of cellobiose and glucose concentrations, pH of the solution, temperature, and dielectric constant, using isopropanol–buffer mixtures. The results show that (i) there is a marked activation of the reaction by initial glucose concentrations of 4 × 10−3 M to 9 × 10−2 M and strong inhibition of the reaction at higher initial concentrations, (ii) the log rate – pH curve has a maximum at pH 5.2 and enzyme pK values of 3.5 and 6.8, (iii) the energy of activation at pH 5.1 is 10.2 kcal mol−1 over the temperature range 5–56 °C, and (iv) the rate decreases from 0 to 20% (v/v) isopropanol.The hydrolysis by cellobiase (EC 3.2.1.21) of p-nitrophenyl-β-D-glucoside was examined by pre-steady-state methods in which [Formula: see text], and by steady-state methods as a function of pH and temperature. The results show (i) a value for k2 of 21 s−1 at pH 7.0 (where k2 is the rate constant for the second step in the assumed two-intermediate mechanism [Formula: see text]) (ii) a log rate–pH curve, significantly different from that for hydrolysis of cellobiose, in which the rate increases with decreasing pH below pH 4.5, is constant in the region pH 4.5–6, and decreases above pH 6 (exhibiting an enzyme pK value of 7.3), and (iii) an activation energy of 12.5 kcal mol−1 at pH 5.7 over the temperature range 10–60 °C.

Compressive creep of dense Bi2Sr1.7CaCu2Ox

1992 ◽  
Vol 7 (9) ◽  
pp. 2360-2364 ◽  
Author(s):  
J.L. Routbort ◽  
K.C. Goretta ◽  
D.J. Miller ◽  
D.B. Kazelas ◽  
C. Clauss ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Activation Energy ◽  
Transmission Electron Microscopy ◽  
Steady State ◽  
Steady State Creep ◽  
Steady State Creep Rate ◽  
Lower Stress ◽  
Dislocation Glide ◽  
Transmission Electron ◽  
Partial Pressures

Dense polycrystalline Bi2Sr1.7CaCu2Ox (2212) was deformed from 780–835 °C in oxygen partial pressures, Po2, of 103 to 2 × 104 Pa. Results could be divided into two stress regimes: one at lower stress in which the steady-state creep rate, ∊, was proportional to stress, γ, having an activation energy of 990 ± 190 kJ/mole and being independent of PO2, and another at higher stress in which ∊ was proportional to σn, with n ≍ 5–6. Transmission electron microscopy supported the interpretation that in the lower-stress viscous regime, creep was controlled by diffusion, whereas dislocation glide and microcracking were responsible for strain accommodation at higher stresses.

Effect of Off-Stoichiometry on the Creep Behavior of Binary and Ternary Ni3Al

1990 ◽  
Vol 213 ◽  
Author(s):  
Tohru Hayashi ◽  
Tetsumori Shinoda ◽  
Yoshinao Mishima ◽  
Tomoo Suzuki
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Power Law ◽  
Creep Behavior ◽  
Creep Resistance ◽  
Steady State Creep ◽  
Steady State Creep Rate ◽  
Creep Equation ◽  
Ternary Element ◽  
Ternary Additions

ABSTRACTCompressive creep behavior is investigated In polycrystalline Ni3Al intermetallic compounds in which the focus is put on the effect of offstoichiometry and ternary additions of Ti, Ta, V and Co on the creep resistance of the compounds. In all cases, the steady-state creep rate has the power-law type dependence on the applied stress. The stress exponent thereby obtained leads us to regard the creep behavior of the compound to be of the Class I type. It is shown that the creep resistance Increases with increasing Ni concentration on both sides of the stoichiometric Ni3Al composition and a discontinuity exists in the variation at stoichiometry. The gap at the discontinuity becomes clearer by the addition of ternary element in most cases as compared to the binary Ni3Al. Although the exact reason for the phenomenon is not clearly understood at present, it is shown that it could be interpreted by the concentration dependence of activation energy in the power-law type creep equation.

scholarly journals THE STEADY-STATE CREEP OF HIGH-PURITY PLUTONIUM

1965 ◽  
Author(s):  
R Nelson ◽  
T Bierlein ◽  
F Bowman
Keyword(s):  
Steady State ◽  
High Purity ◽  
Steady State Creep

scholarly journals MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Sagar Masuti ◽  
Sylvain Barbot
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Upper Mantle ◽  
Physical Mechanism ◽  
Transient Creep ◽  
Steady State Creep ◽  
Postseismic Deformation ◽  
Nonlinear Stress ◽  
Dry And Wet Conditions ◽  
Flow Law

AbstractThe rheology of the upper mantle impacts a variety of geodynamic processes, including postseismic deformation following great earthquakes and post-glacial rebound. The deformation of upper mantle rocks is controlled by the rheology of olivine, the most abundant upper mantle mineral. The mechanical properties of olivine at steady state are well constrained. However, the physical mechanism underlying transient creep, an evolutionary, hardening phase converging to steady state asymptotically, is still poorly understood. Here, we constrain a constitutive framework that captures transient creep and steady state creep consistently using the mechanical data from laboratory experiments on natural dunites containing at least 94% olivine under both hydrous and anhydrous conditions. The constitutive framework represents a Burgers assembly with a thermally activated nonlinear stress-versus-strain-rate relationship for the dashpots. Work hardening is obtained by the evolution of a state variable that represents internal stress. We determine the flow law parameters for dunites using a Markov chain Monte Carlo method. We find the activation energy $$430\pm 20$$ 430 ± 20   and $$250\pm 10$$ 250 ± 10  kJ/mol for dry and wet conditions, respectively, and the stress exponent $$2.0\pm 0.1$$ 2.0 ± 0.1 for both the dry and wet cases for transient creep, consistently lower than those of steady-state creep, suggesting a separate physical mechanism. For wet dunites in the grain-boundary sliding regime, the grain-size dependence is similar for transient creep and steady-state creep. The lower activation energy of transient creep could be due to a higher jog density of the corresponding soft-slip system. More experimental data are required to estimate the activation volume and water content exponent of transient creep. The constitutive relation used and its associated flow law parameters provide useful constraints for geodynamics applications. Graphical Abstract

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