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.

A Weakest-Link Model for the Prediction of Fatigue Crack Growth Rate

1978 ◽  
Vol 100 (2) ◽  
pp. 170-174 ◽  
Author(s):  
Kong Ping Oh
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Average Rate ◽  
Joint Probability ◽  
Random Variable ◽  
Weakest Link ◽  
Link Theory ◽  
Link Model ◽  
Joint Probability Density

A weakest-link theory is proposed for analyzing the rate of fatigue crack growth. The joint probability density of a fatigue crack growing an amount X between x and x+dx, and in time η between N and N+dN cycles is derived from an initial probability function. The rate of crack growth is then obtained as the expectation of the random variable (X/η). It is shown that the average rate of crack growth obeys the power law for small ΔK, and that the power is a function of the shape parameter in the Weibull distribution.

Scaling of Static Fracture of Quasi-Brittle Structures: Strength, Lifetime, and Fracture Kinetics

2012 ◽  
Vol 79 (3) ◽  
Author(s):  
Jia-Liang Le ◽  
Zdeněk P. Bažant
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Size Effect ◽  
Crack Growth ◽  
Failure Probability ◽  
Structural Strength ◽  
Chain Model ◽  
Weakest Link

The paper reviews a recently developed finite chain model for the weakest-link statistics of strength, lifetime, and size effect of quasi-brittle structures, which are the structures in which the fracture process zone size is not negligible compared to the cross section size. The theory is based on the recognition that the failure probability is simple and clear only on the nanoscale since the probability and frequency of interatomic bond failures must be equal. The paper outlines how a small set of relatively plausible hypotheses about the failure probability tail at nanoscale and its transition from nano- to macroscale makes it possible to derive the distribution of structural strength, the static crack growth rate, and the lifetime distribution, including the size and geometry effects [while an extension to fatigue crack growth rate and lifetime, published elsewhere (Le and Bažant, 2011, “Unified Nano-Mechanics Based Probabilistic Theory of Quasibrittle and Brittle Structures: II. Fatigue Crack Growth, Lifetime and Scaling,” J. Mech. Phys. Solids, 1322–1337), is left aside]. A salient practical aspect of the theory is that for quasi-brittle structures the chain model underlying the weakest-link statistics must be considered to have a finite number of links, which implies a major deviation from the Weibull distribution. Several new extensions of the theory are presented: (1) A derivation of the dependence of static crack growth rate on the structure size and geometry, (2) an approximate closed-form solution of the structural strength distribution, and (3) an effective method to determine the cumulative distribution functions (cdf’s) of structural strength and lifetime based on the mean size effect curve. Finally, as an example, a probabilistic reassessment of the 1959 Malpasset Dam failure is demonstrated.

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.

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.

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

Subcritical Crack Growth and Long-Term Strength in Rock and High-Strength and Ultra Low-Permeability Concrete

2009 ◽  
Vol 58 (6) ◽  
pp. 525-532 ◽  
Author(s):  
Yoshitaka NARA ◽  
Masafumi TAKADA ◽  
Daisuke MORI ◽  
Hitoshi OWADA ◽  
Tetsuro YONEDA ◽  
...  
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
High Strength ◽  
Low Permeability ◽  
Term Strength
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