Activation energy jump in the force dependence of the steady-state creep rate during tension of aluminum and lead

2012 ◽  
Vol 57 (9) ◽  
pp. 1204-1207
Author(s):  
A. I. Petrov ◽  
M. V. Razuvaeva
2005 ◽  
Vol 482 ◽  
pp. 319-322
Author(s):  
Jan Kohout

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.


1990 ◽  
Vol 5 (12) ◽  
pp. 2766-2770 ◽  
Author(s):  
K. C. Goretta ◽  
J. L. Routbort ◽  
A. C. Biondo ◽  
Y. Gao ◽  
A. R. de Arellano-López ◽  
...  

YBa2Cu3Ox was deformed from 850 to 980 °C in oxygen partial pressures of 103 to 105 Pa. Steady-state creep rate, ̇, for P(O2) from 104 to 105 Pa could be expressed as ̇ = Aσ1.0 (GS)−2.8±0.6 exp −(970 ± 130 kJ/mole)/RT, where A is a constant, σ the steady-state stress, GS the average grain size, and R and T have their usual meanings, For P(O2) from 103 to 3 ⊠ 103 Pa, the activation energy decreased to about 650 kJ/mole and for a given temperature creep kinetics were much faster. The data and microscopic observations indicated that creep occurred by diffusional flow. Comparisons with diffusion data for YBa2Cu3Ox suggested that Y or Ba may be rate-controlling diffusing species.


2006 ◽  
Vol 326-328 ◽  
pp. 553-556
Author(s):  
Seon Jin Kim ◽  
Yu Sik Kong ◽  
Young Jin Roh ◽  
Won Taek Jung

This paper deals with the statistical properties of short time creep rupture characteristic values (for example, creep rupture time, steady state creep rate, total creep rate, initial strain, etc.) in STS304 stainless steels. From short time creep rupture tests performed by constant stresses at three different elevated temperatures 600, 650 and 700, the scatter and probability distributions were investigated for rupture time, total creep rate, steady state creep rate, initial strain, and others. The effect of temperature on the statistical scatter of rupture time was the smallest at 700. The effect of stress on the statistical scatter of rupture time was smaller with increasing stresses. The probability distributions of short time creep rupture data were well followed 2-parameter Weibull.


2006 ◽  
Vol 326-328 ◽  
pp. 1309-1312
Author(s):  
Seon Jin Kim ◽  
Yu Sik Kong ◽  
Young Join Noh ◽  
Won Taek Jung ◽  
Sang Woo Kwon

In this study, the creep rupture tests of STS304 stainless steels were investigated at three different elevated temperatures of 600, 650 and 700 under the constant creep stresses. Creep rupture characteristics such as creep stress, creep rupture time, steady state creep rate and so on were evaluated. The behaviors of creep rate curve and initial strain are compared at three different elevated temperatures. The stress exponent (n) at 600, 650 and 700 based on steady state creep rate showed 22.5, 20.6 and 11.4 respectively. By increasing the temperature, the stress exponent is decreased. At the temperature of 700, the lowest stress exponents are shown and this behavior is also observed in the case of stress exponent based on rupture time. The creep life prediction by LMP method is presented and the equation of this result is as follows: T(logtr+20)=-0.005152-14.56+24126.


1992 ◽  
Vol 7 (9) ◽  
pp. 2360-2364 ◽  
Author(s):  
J.L. Routbort ◽  
K.C. Goretta ◽  
D.J. Miller ◽  
D.B. Kazelas ◽  
C. Clauss ◽  
...  

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.


1976 ◽  
Vol 43 (1) ◽  
pp. 28-32
Author(s):  
V. M. Radhakrishnan

Investigations have been carried out to study the effect of oscillating stress on the strain accumulation in pure aluminum at elevated temperature. The creep rate under the oscillating stress has been found to increase with increasing value of the alternating component of the stress and is somewhat higher than the steady-state creep rate corresponding to the maximum stress, in the range of temperature used. The rupture time is inversely proportional to the cyclic creep rate. A model for obtaining the reference stress has been proposed and based on the data obtained, a parametric approach is presented.


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