Fatigue Strength Degradation by Irreversible Hydrogen in Cold Drawn Eutectoid Steels

2011 ◽  
Vol 462-463 ◽  
pp. 188-193
Author(s):  
Masanori Nakatani ◽  
Kohji Minoshima
Keyword(s):  
Activation Energy ◽  
Fatigue Strength ◽  
Hydrogen Embrittlement ◽  
High Sensitivity ◽  
Fatigue Tests ◽  
Strength Degradation ◽  
Trap Site ◽  
High Activation ◽  
High Activation Energy ◽  
Higher Sensitivity

The fatigue tests were conducted for cold-drawn eutectoid steels having different activation energies and microstructures to investigate the mechanism of fatigue strength degradation by irreversible hydrogen. The fatigue strength of a sample with low activation energy was decreased by irreversible hydrogen, whereas the fatigue strength of a sample with high activation energy was not. When the activation energy for irreversible hydrogen becomes small, the desorption of irreversible hydrogen from its trap site is easily induced by cyclic loading, which results in a decrease in fatigue strength. When a sample having high activation energy was annealed at 473 K, the fatigue strength was decreased by irreversible hydrogen although the activation energy barely changed. This is because the precipitation of fine carbides due to annealing causes higher sensitivity to hydrogen embrittlement. High sensitivity to hydrogen embrittlement was concluded to induce the fatigue strength degradation by irreversible hydrogen. Therefore, the degradation of fatigue strength by irreversible hydrogen depends on the activation energy and sensitivity to hydrogen embrittlement.

Front instability in a condensed phase combustion model

2015 ◽  
Vol 4 (3) ◽  
pp. 153-176 ◽  
Author(s):  
Alexis Bonnet ◽  
Fathi Dkhil ◽  
Elisabeth Logak
Keyword(s):  
Activation Energy ◽  
Condensed Phase ◽  
Linear Instability ◽  
Combustion Model ◽  
Energy Limit ◽  
High Activation ◽  
Front Solution ◽  
High Activation Energy ◽  
Linearized Problem ◽  
Existence Of Zeros

AbstractWe consider a condensed phase (or solid) combustion model and its linearization around the travelling front solution. We construct an Evans function to characterize the eigenvalues of the linearized problem. We estimate this functional in the high activation energy limit. We deduce the existence of zeros with nonnegative real part for high activation energy, which proves the linear instability of the travelling front solution.

scholarly journals Gas-phase detonation propagation in mixture composition gradients

2012 ◽  
Vol 370 (1960) ◽  
pp. 567-596 ◽  
Author(s):  
D. A. Kessler ◽  
V. N. Gamezo ◽  
E. S. Oran
Keyword(s):  
Activation Energy ◽  
Reaction Model ◽  
Single Step ◽  
Mixture Composition ◽  
Composition Gradient ◽  
Detonation Properties ◽  
High Activation ◽  
Zone Structure ◽  
Detonation Cell ◽  
High Activation Energy

The propagation of detonations through several fuel–air mixtures with spatially varying fuel concentrations is examined numerically. The detonations propagate through two-dimensional channels, inside of which the gradient of mixture composition is oriented normal to the direction of propagation. The simulations are performed using a two-component, single-step reaction model calibrated so that one-dimensional detonation properties of model low- and high-activation-energy mixtures are similar to those observed in a typical hydrocarbon–air mixture. In the low-activation-energy mixture, the reaction zone structure is complex, consisting of curved fuel-lean and fuel-rich detonations near the line of stoichiometry that transition to decoupled shocks and turbulent deflagrations near the channel walls where the mixture is extremely fuel-lean or fuel-rich. Reactants that are not consumed by the leading detonation combine downstream and burn in a diffusion flame. Detonation cells produced by the unstable reaction front vary in size across the channel, growing larger away from the line of stoichiometry. As the size of the channel decreases relative to the size of a detonation cell, the effect of the mixture composition gradient is lessened and cells of similar sizes form. In the high-activation-energy mixture, detonations propagate more slowly as the magnitude of the mixture composition gradient is increased and can be quenched in a large enough gradient.

Anomalous high activation energy for creep in nanostructured 3YTZP/Ni cermets

2007 ◽  
Vol 27 (11) ◽  
pp. 3295-3299 ◽  
Author(s):  
A. Morales-Rodríguez ◽  
D. Gómez-García ◽  
T. Rodriguez-Suarez ◽  
S. Lopez-Esteban ◽  
C. Pecharroman ◽  
...  
Keyword(s):  
Activation Energy ◽  
High Activation ◽  
High Activation Energy

Cu-based metal-organic frameworks for highly sensitive X‑ray detector

2021 ◽  
Author(s):  
Zheng Li ◽  
Shuquan Chang ◽  
Haiqian Zhang ◽  
Yong Hu ◽  
Yulong Huang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Metal Organic Frameworks ◽  
High Activation ◽  
X Ray ◽  
High Activation Energy ◽  
Highly Sensitive ◽  
Metal Organic

Here, we constructed Pb-free Cu-DABDT-MOFs-based (DABDT = 2,5-diamino-1,4-benzenedithiol dihydrochloride) X-ray detectors. Combined with the advantage of high activation energy, Cu-DABDT-MOFs-based detector can effectively generate and capture electron under X-ray exposure...

The Mechanism of Superplastic Deformation with High Activation Energy

1991 ◽  
Vol 66-69 ◽  
pp. 1421-1424
Author(s):  
András Juhász ◽  
P. Tasnádi ◽  
Nguyen Q. Chinh ◽  
I. Kovács
Keyword(s):  
Activation Energy ◽  
Superplastic Deformation ◽  
High Activation ◽  
High Activation Energy
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