Dynamic Embrittlement Of Beryllium-Strengthened Copper In Air

1995 ◽  
Vol 409 ◽  
Author(s):  
Ranjani C. Muthiah ◽  
C. J. McMahon ◽  
Amitava Guha
Keyword(s):  
Oxygen Diffusion ◽  
Model Material ◽  
Time To Failure ◽  
Temperature Model ◽  
Kcal Mole ◽  
Intergranular Cracking ◽  
Diffusion Controlled ◽  
Intergranular Brittle Fracture ◽  
Stress Dependent ◽  
Dynamic Embrittlement

AbstractA precipitation-hardened Cu-0.26%Be alloy is used as a low-temperature model material for “dynamic embrittlement”, or quasi-static diffusion-controlled intergranular brittle fracture. This alloy is shown to undergo intergranular cracking in air at 150°C and to be almost free of this cracking in 2×10−6 Torr vacuum at 200°C. The time to failure is highly stress dependent. The temperature dependence of cracking was found to be 30 kcal/mole. This is about 50% greater than the activation energy for oxygen diffusion in copper, but the present experiments also include an unknown incubation time.

Quasi-Static Brittle Fracture

1998 ◽  
Vol 539 ◽  
Author(s):  
J. A. Pfaendtner ◽  
R. C. Muthiah ◽  
C. J. McMahon
Keyword(s):  
Brittle Fracture ◽  
Recent Work ◽  
Diffusion Controlled ◽  
Intergranular Brittle Fracture ◽  
Dynamic Embrittlement

AbstractRecent work on the phenomenon of diffusion-controlled quasi-static brittle fracture, known as dynamic embrittlement, is reviewed here with reference to sulfur-induced embrittlement of steel, tin-induced embrittlement of Cu-Sn alloys, and oxygen-induced embrittlement of copper-based and nickel-based alloys. The mechanisms of this generic form of intergranular brittle fracture are discussed.

scholarly journals Time to failure assessment of products at service conditions from accelerated lifetime tests with stress-dependent spread in life

2007 ◽  
Vol 27 (2) ◽  
pp. 209-233 ◽  
Author(s):  
Enrique López Droguett ◽  
Ali Mosleh
Keyword(s):  
Comparative Analysis ◽  
Shape Parameter ◽  
Scale Parameter ◽  
Time To Failure ◽  
Failure Assessment ◽  
Accelerated Lifetime ◽  
Lifetime Testing ◽  
Service Conditions ◽  
Stress Dependent ◽  
Parameter Dependency

In accelerated lifetime testing (ALT) the assumption of stress-independent spread in life is commonly used and accepted because the resulting models are typically easier to use and data or past experience suggest that such a constrain is sometimes valid. However in many situations and with a variety of products the spread in life does depend on stress, i.e., the failure mechanism is not the same for all stress levels. In this paper the assessment of product time to failure at service conditions from ALT with stress-dependent spread is addressed by formulating a Bayesian framework where the time to failure follows a Weibull distribution, scale parameter dependency on stress is given by the Power Law, and two cases for the dependency between shape parameter and stress are discussed: linear relationship and, in order to allow a comparative analysis, stress-independent shape parameter. A previously published dataset is used to illustrate the procedure.

Primary products and processes in the γ-radiolysis of 2-methyltetrahydrofuran

1965 ◽  
Vol 285 (1402) ◽  
pp. 319-338 ◽  
Keyword(s):  
Glassy Phase ◽  
Kcal Mole ◽  
Radical Species ◽  
Molecule Reaction ◽  
Positive Ions ◽  
Primary Products ◽  
Diffusion Controlled ◽  
Thermal Bleaching ◽  
The Matrix ◽  
Kinetics Of

From a study of the u. v., visible, near i. r. and e. s. r. spectra induced by γ -irradiation at 77°K in glassy MTHF and in glassy MTHF containing various additives and from a study of controlled temperature increases on these spectra, the following conclusions are drawn. (1) The primary products of the radiolysis are electrons ( e - ) and positive ions ( MTHF + ) which undergo a rapid ion-molecule reaction to give O CH 3 radicals ( R ⋅). (2) e - can either be trapped in the glassy MTHF matrix or can be captured by either napththalene, ferric chloride, carbon tetrachloride, nitrous oxide or trans -stilbene if these substances are present. (3) The e - T are bleachable by light or heat and disappear independently of the radicals R⋅ without either augmentation of R⋅ or the production of any new radical species. (4) e - T and R⋅ disappear thermally and independently by second-order reactions, the rate constants being K e - + e - (M -1 S -1 ) = 10 12⋅4±1⋅1 exp ─ [0⋅85 ± 0⋅10 kcal/mole/ R ( T ─ 75)] and K R˙ + R˙ (M -1 S -1 ) = 10 13⋅3±1⋅4 exp ─ [1⋅20 ± 0⋅15 kcal/mole/ R ( T ─ 75)]. These rate expressions suggest that both reactions are diffusion controlled at low temperatures in the glassy phase. (5) The kinetics of the thermal bleaching of e - T indicate that the electrons migrate distances of about 150 Å from their parent positive ions before being trapped in the matrix. (6) The effect of FeCl 3 in reducing the formation of e - T at 77°K and its lack of effect on the thermal bleaching of e - T suggests that the reaction e - + FeCl 3 → FeCl 2 + Cl - only occurs before the electron is thermalized.

Quasi-static intergranular brittle fracture: Dynamic embrittlement

1995 ◽  
Vol 45 (11) ◽  
pp. 965-978 ◽  
Author(s):  
C. J. McMahon ◽  
J. A. Pfaendtner ◽  
R. C. Muthiah
Keyword(s):  
Brittle Fracture ◽  
Intergranular Brittle Fracture ◽  
Dynamic Embrittlement

scholarly journals The Effects of Temperature on the Leaching Behavior of Cement Waste Forms - The Cement/Sodium Sulfate System

1989 ◽  
Vol 176 ◽  
Author(s):  
Mark Fuhrmann ◽  
Richard Pietrzak ◽  
John Heiser ◽  
Eena-Mai Franz ◽  
Peter Colombo
Keyword(s):  
Sodium Sulfate ◽  
Elevated Temperatures ◽  
Effective Diffusion ◽  
Finite Cylinder ◽  
Kcal Mole ◽  
Experimental Conditions ◽  
Waste Forms ◽  
Diffusion Controlled ◽  
Increasing Temperature ◽  
Relationship Of

ABSTRACTThe leaching mechanisms of simulated low-level radioactive waste forms are being determined as support for development of an accelerated leach test. Two approaches are being used: (1) comparison of leaching data with results of a model that describes diffusion from a finite cylinder, and (2) observation of the leaching process at temperatures between 20°C and 65°C. To provide results that can be used for modeling, leaching at elevated temperatures must change neither the leaching mechanism nor the structural controls of leaching such as the porosity. Releases of 137Cs, 85Sr, calcium, sodium and potassium from portland cement containing sodium sulfate, as a simulated evaporator sludge, have been determined under a variety of experimental conditions. Data from the leach tests were compared to model results for diffusion from the finite cylinder. While most leaching appears to be diffusion controlled, notable exceptions occur. For all samples, activation energies ranging between 6 and 11 Kcal/mole have been calculated from the relationship of the effective diffusion coefficient to increasing temperature, close to the expected value of 5 Kcal/mole for diffusion.

A thermocouple method of following the non-stationary state of chemical reactions - III. The evaluation of velocity coefficients and energies of activation for the propagation and termination reactions for the initial and later stages of the polymerization of butyl acrylate

1959 ◽  
Vol 249 (1259) ◽  
pp. 445-454 ◽  
Keyword(s):  
Stationary State ◽  
Chemical Reactions ◽  
Butyl Acrylate ◽  
Energy Of Activation ◽  
Kcal Mole ◽  
Initial Value ◽  
Diffusion Controlled ◽  
Thermocouple Method ◽  
Velocity Coefficient

The changes which occur in the velocity coefficients and energies of activation for the propagation and termination reactions in the polymerization of butyl acrylate photosensitized with I . l'-azo-bis- cyclohexane carbonitrile have been studied. The rate increases slightly during the first 25% conversion and then gradually decreases throughout the remainder of the reaction, while the overall energy of activation increases slightly at later stages of the reaction. Beyond 20% conversion the energy of activation for the propagation reaction remains in the region of 13 kcal/mole and that for the termination reaction at about 17 kcal/mole. The high values of these energies of activation are consistent with both the propagation and termination reactions becoming diffusion controlled by about 20% conversion. The velocity coefficient for the propagation reaction decreases from an initial value of 2100 to 44 l. mole- 1 s- 1 at about 75% polymerization, while that for the termination reaction changes from 3.3 x 10 7 initially to 7.3 x 10 6 1. mole- 1 s- 1 at about 75% conversion.

Improving the Diffusion Controlled Cementation of Cadmium Ions Using Reciprocating Fixed Bed of Zinc Rings

2011 ◽  
Vol 312-315 ◽  
pp. 694-699 ◽  
Author(s):  
A.H. El-Shazly ◽  
Ashraf A. Mubarak ◽  
Hesham S. Bamufleh
Keyword(s):  
Arrhenius Equation ◽  
Fixed Bed ◽  
Effect Of Temperature ◽  
Vibration Velocity ◽  
Kcal Mole ◽  
Cadmium Ions ◽  
Bed Height ◽  
Diffusion Controlled ◽  
Ring Diameter ◽  
Kinetics Of

The aim of the present work is to investigate the effect of pulsation on improving the rate of the diffusion controlled cementation of cadmium ions using reciprocating fixed bed of zinc rings. The kinetics of the cementation reaction was investigated under different conditions of initial concentration of cadmium ions, frequency and amplitude of oscillation (vibration velocity), zinc ring diameter, bed diameter, bed height and temperature. The effect of temperature was found to fit the Arrhenius equation with an activation energy of 7.58 kcal/mole which confirms the diffusion controlled nature of the reaction. A dimensionless correlation in the form of Sh = 6.9 Re0.45 Sc0.33 (Bd/Bh)0.89 was deduced. The industrial application of the obtained results was discussed.

The Effects of Applied Stress and Test Temperature on the Environment-Induced Cracking Behavior of Carbon Steel in NH4NO3 Solution

2013 ◽  
Vol 684 ◽  
pp. 139-143
Author(s):  
Kenichi Koide ◽  
Akihiro Iwase ◽  
Rokuro Nishimura
Keyword(s):  
Carbon Steel ◽  
Applied Stress ◽  
Test Temperature ◽  
Hydrogen Permeation ◽  
Film Formation ◽  
Constant Load ◽  
Time To Failure ◽  
Intergranular Cracking ◽  
Cracking Behavior ◽  
Fracture Appearance

The effects of applied stress and test temperature on the environment-induced cracking (EIC) behavior of carbon steel in 5 kmol/m3 NH4NO3 solution were investigated by using constant load method. The three parameters (time to failure (tf), steady state elongation rate (lss) and transition time to time to failure ratio (tss/tf)) were obtained from a corrosion elongation curve. The relationships between applied stress and the three parameters were divided into three regions; the stress-dominated, the EIC-dominated and the corrosion-dominated regions. Under an applied stress of 225 MPa (in the EIC-dominated region), the test temperature dependences of the three parameters were investigated. Although tf decreased with increasing test temperature above 323 K, it became constant independent of test temperature under 323 K. Whenever the EIC takes place, the relationship between log tf and log lss become a good straight line with a slope of -1.1 irrespective applied stress and test temperature, which means that lss becomes a parameter for predicting tf. In addition, the fracture appearance in the EIC-dominated region was intergranular. From the results obtained, the intergranular cracking of carbon steel was discussed in terms of film formation, dissolution and hydrogen permeation.

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