Kinetics of Subcritical Crack Growth and Deformation in a High Strength Steel

1973 ◽  
Vol 95 (1) ◽  
pp. 2-9 ◽  
Author(s):  
J. D. Landes ◽  
R. P. Wei
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Activation Energies ◽  
Steady State Creep ◽  
Deformation Kinetics ◽  
Deformation Processes ◽  
Apparent Activation Energies ◽  
Kinetics Of

The kinetics of subcritical crack growth under sustained loading in a chemically inert environment (dehumidified argon) and the companion deformation kinetics were determined to examine the possible relationship between the crack growth and deformation processes in an AISI 4340 steel tempered at 400 deg F (∼205 degC). Crack growth experiments were carried out over a range of temperatures from 20 to 140 deg C, using the crack tip stress intensity factor K to chacterize the mechanical crack driving force. Deformation kinetics were determined as a function of deformed structure either at constant load or by a strain rate cycling procedure over the same range of temperatures. Detectable crack growth (with rates above 10−5 ipm) in dehumidified argon occurred at K levels exceeding about 70 percent of Kc at room temperature and 50 percent of Kc at the higher temperatures. Crack growth exhibited transient, steady-state and tertiary stages of growth, akin to creep, in agreement with the results of Li, et al. Experimental data indicate that subcritical crack growth in dehumidified argon is controlled by thermally activated processes, with apparent activation energies in the range of 11,000 to 18,000 cal/mole. This range of apparent activation energies is in general agreement with an observed range of 12,000 to 28,000 cal/mole for steady-state creep in this material. The apparent activation energies for steady-state creep were found to be dependent on flow stress and structure. Based on the similarity between the observed crack growth and deformation behaviors and on the order of magnitude agreement between the apparent activation energies, it is reasonable to consider that subcritical crack growth in inert environments is controlled by the time dependent deformation processes occurring at the crack tip. A model for relating steady-state crack growth and steady-state creep is suggested, and is shown to correlate well with experimental data.

High-temperature deformation and fracture of Bi–Sr–Ca–Cu–O superconductors

1994 ◽  
Vol 9 (3) ◽  
pp. 541-547 ◽  
Author(s):  
K.C. Goretta ◽  
E.J. Zamirowski ◽  
J.M. Calderoñ-Moreno ◽  
D.J. Miller ◽  
Nan Chen ◽  
...  
Keyword(s):  
Dislocation Motion ◽  
Steady State Creep ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Creep Response ◽  
Transmission Electron ◽  
Deformation And Fracture ◽  
Deformation Processes ◽  
Apparent Activation Energies ◽  
Kinetics Of

Dense polycrystalline Bi2Sr2Cu2Ox (2201), Bi2Sr2CaCu2Ox (2212), and (Bi, Pb)2Sr2Ca2Cu3Ox (2223) specimens were compressed in air at 730–835 °C. All of the materials exhibited an apparent steady-state creep response. Strain rate was proportional to stress to the 3.1–3.8 power. Apparent activation energies for the deformation processes were 520 ± 50 kJ/mole for the 2201, 630 ± 210 kJ/mole for the 2212, and 960 ± 210 kJ/mole for the 2223. Transmission electron microscopy revealed substantial generation and propagation of basal-plane dislocations during deformation. Few nonbasal-plane dislocations were observed. Intergranular fracture was evident in all deformed samples, and intragianular fracture was evident along the basal planes of some grains. It is suggested that the kinetics of fracture were determined by dislocation motion within the grains.

Numerical evaluation of subcritical crack growth kinetics in structural adhesive joints under long static loading with cohesive zone model and experimental data

2021 ◽  
Vol 10 ◽  
pp. 74-84
Author(s):  
A. A. Ustinov ◽  
◽  
P. G. Babayevsky ◽  
N. A. Kozlov ◽  
N. V. Saliyenko ◽  
...  
Keyword(s):  
Experimental Data ◽  
Crack Growth ◽  
Static Loading ◽  
Cohesive Zone ◽  
Subcritical Crack Growth ◽  
Cohesive Zone Model ◽  
Adhesive Joints ◽  
Zone Model ◽  
Structural Adhesive ◽  
Kinetics Of

The article proposes a numerical method for modeling and calculating the kinetics of subcritical crack growth and creating kinetic G-V diagrams for structural adhesive joints under prolonged static loading. The load was set by the global subcritical crack opening according to mode I. Modeling and calculations were carried out using a cohesive zone model implanted into the finite element method in the ANSYS software package. The parameters of the cohesive zone law and the kinetics of subcritical crack growth were experimentally determined for samples in the form of a double cantilever beam made of aluminum alloy plates glued with industrial grade epoxy glue. Comparison of the calculated and experimental data showed a good correlation.

Kinetic analysis of mechanism of intestinal Na+-dependent sugar transport

1985 ◽  
Vol 248 (5) ◽  
pp. C498-C509 ◽  
Author(s):  
D. Restrepo ◽  
G. A. Kimmich
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Sugar Transport ◽  
Enzyme Kinetic ◽  
Steady State Distribution ◽  
State Distribution ◽  
Least Squares Fit ◽  
Coupling Stoichiometry ◽  
Rate Limiting ◽  
Kinetics Of

Zero-trans kinetics of Na+-sugar cotransport were investigated. Sugar influx was measured at various sodium and sugar concentrations in K+-loaded cells treated with rotenone and valinomycin. Sugar influx follows Michaelis-Menten kinetics as a function of sugar concentration but not as a function of Na+ concentration. Nine models with 1:1 or 2:1 sodium:sugar stoichiometry were considered. The flux equations for these models were solved assuming steady-state distribution of carrier forms and that translocation across the membrane is rate limiting. Classical enzyme kinetic methods and a least-squares fit of flux equations to the experimental data were used to assess the fit of the different models. Four models can be discarded on this basis. Of the remaining models, we discard two on the basis of the trans sodium dependence and the coupling stoichiometry [G. A. Kimmich and J. Randles, Am. J. Physiol. 247 (Cell Physiol. 16): C74-C82, 1984]. The remaining models are terter ordered mechanisms with sodium debinding first at the trans side. If transfer across the membrane is rate limiting, the binding order can be determined to be sodium:sugar:sodium.

Local stress and strain during crack growth by steady state creep

1977 ◽  
Vol 12 (10) ◽  
pp. 2099-2108 ◽  
Author(s):  
J. T. Barnby ◽  
R. D. Nicholson
Keyword(s):  
Steady State ◽  
Crack Growth ◽  
Local Stress ◽  
Steady State Creep ◽  
Stress And Strain

Interfacial reactions in multilayers intended for microelectronics devices

1998 ◽  
Vol 514 ◽  
Author(s):  
X. Federspiel ◽  
F. Voiron ◽  
M. Ignat ◽  
T. Marieb ◽  
H. Fujimoto
Keyword(s):  
Phase Formation ◽  
Reaction Rate ◽  
Experimental Approach ◽  
Intermetallic Phase ◽  
Activation Energies ◽  
Interfacial Reactions ◽  
Scanning Calorimetry ◽  
Back Scattering ◽  
Apparent Activation Energies ◽  
Kinetics Of

ABSTRACTThe knowledge of the reaction kinetics which can occur at an interface of a couple of materials, remains a crucial issue to establish the structural limits of a diffusion barrier intended for microelectronic structures.In the past years, the interfacial reactions activated at an interface of a couple of materials, as for example aluminum and titanium, have been analyzed extensively using different experimental tools, as for example: Ruthreford Back Scattering (thickness determination) and Differential Scanning Calorimetry (DSC). Then, these experimental methods were useful to deduce parameters, characterizing the interfacial reactions in bulk samples: apparent activation energies, enthalpy of formation. Because in thin films, the kinetics of the reactions that can be activated at an interface will be different; we studied interfacial reactions in submicronic Al/Ti layers.Taking advantage of the accuracy of the DSC (reaction rate determinations and detection of earlier stages of intermetallic phase formation), our experimental approach consisted in a series of isothermal and non-isothermal DSC experiments on submicron Al/Ti layered structures. From the reaction rate determination, analytical methods as the Kissinger Ozawa approach were used, to determine the apparent activation energies of the phase formation. Also the results allowed to model and discuss the first steps of the interfacial reaction.

scholarly journals Dissolution of Tunisian phosphate ore by a mixture of sulfuric and phosphoric acid: Kinetics study by means of differential reaction calorimetry

2019 ◽  
Vol 55 (1) ◽  
pp. 9-19
Author(s):  
Olfa Lachkar-Zamouri ◽  
Khemaies Brahim ◽  
Faten Bennour ◽  
Ismail Khattech
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Dissolution Rate ◽  
Dissolution Kinetics ◽  
Reaction Model ◽  
Reaction Calorimetry ◽  
Phosphate Ore ◽  
Differential Reaction ◽  
Apparent Activation Energies ◽  
Kinetics Of

A mixture of phosphoric and sulfuric acid was used to investigate the dissolution kinetics of phosphate ore by Differential Reaction Calorimetry (DRC). The effect of the solid-to-iquid ratio, concentration, stirring speed, particle size and temperature of the reaction is examined. It was established that the dissolution rate increased with stirring speed and particle size. However, rising the olid-to-iquid ratio, temperature and concentration decreased the dissolution rate. It was determined that the dissolution rate fits in the first order of the pseudo-homogeneous reaction model. Two negative values of apparent activation energies were found in the range of 25 to 60?C. The experimental data were tested by graphical and statistical methods and it was found that the following models were best fitted for the experimental data and an empirical equation for the process was developed. -ln (1 ? x) = [2,2 E-09((S/L)0.75C -0.461G0.447(SS) 0.471exp (2671/T)]t. T? 40?C -ln (1 ? x) = [2,2 E-09((S/L)0.75C -0.461G0.447(SS) 0.471exp (6959/T)]t. T > 45?C

Tensile Creep Behavior of NiAl-9Mo Eutectic Alloy

2005 ◽  
Vol 475-479 ◽  
pp. 763-766 ◽  
Author(s):  
Wei Li Ren ◽  
Jian Ting Guo ◽  
Gu Song Li ◽  
Jian Sheng Wu
Keyword(s):  
Steady State ◽  
Eutectic Alloy ◽  
Creep Behavior ◽  
Dislocation Climb ◽  
Steady State Creep ◽  
Tensile Creep ◽  
Final Fracture ◽  
Colony Boundary ◽  
Kinetics Of ◽  
Nial Matrix

The tensile creep behavior of NiAl-9Mo eutectic alloy has been investigated over a stress range of 50 to 100MPa at the temperatures ranging from 850 to 950°C. All of the creep curves exhibit the very long steady-state stage. The creep parameters and TEM observations indicates the kinetics of the steady-state creep deformation is governed by dislocation climb in the NiAl matrix phase. The crack origination and development at the colony boundary results in the onset of tertiary creep stage and final fracture of the alloy.

scholarly journals Analysis of the Failure of Ceramics Due to Subcritical Crack Growth

1996 ◽  
Vol 118 (3) ◽  
pp. 343-348 ◽  
Author(s):  
Franc¸ois Hild ◽  
Didier Marquis ◽  
Olivier Kadouch ◽  
Jean-Pierre Lambelin
Keyword(s):  
Experimental Data ◽  
Crack Growth ◽  
Failure Probability ◽  
Subcritical Crack Growth ◽  
Weakest Link ◽  
Independent Events ◽  
Zn Ferrite ◽  
Link Theory ◽  
Growth Laws ◽  
Failure Conditions

Failure conditions are assessed when ceramics exhibit Subcritical Crack Growth from preexisting flaws. In the framework of the weakest link theory and independent events hypothesis, a reliability analysis is carried out by modeling flaw distributions and crack growth laws. Experimental data obtained on a spinel Mn Zn ferrite subjected to five different load rates are analyzed by using an expression for the failure probability accounting for Subcritical Crack Growth.

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