scholarly journals Estimation of propagation rate of creep microcracks by using crack length distribution.

1985 ◽  
Vol 34 (386) ◽  
pp. 1340-1345
Author(s):  
Ryuichi OHTANI ◽  
Toshiya KINAMI
Keyword(s):  
Crack Length ◽  
Length Distribution ◽  
Propagation Rate ◽  
Crack Length Distribution

Fracture Simulation of Randomly Cracked Material with Various Crack Length Distributions

2004 ◽  
Vol 261-263 ◽  
pp. 1055-1060 ◽  
Author(s):  
Kazushi Sato ◽  
Toshiyuki Hashida
Keyword(s):  
Numerical Simulation ◽  
Fracture Mechanics ◽  
Crack Length ◽  
Length Distribution ◽  
Tensile Load ◽  
Uniaxial Tensile ◽  
Cracking Behavior ◽  
Fracture Simulation ◽  
Elastic Fracture ◽  
Crack Length Distribution

In this paper, cracking behavior of distributed microcracks is discussed using a numerical simulation. The microcracks are initially distributed in a rectangle region. The directions and locations of the cracks are chosen at random. Three kinds of length distributions are used, such as a uniform length, a random length distribution and a fractal length distribution. The crack propagations from the initially distributed cracks are analyzed under a uniaxial tensile load using liner elastic fracture mechanics. The global behaviors of various crack distribution are studied. Results obtained from the numerical calculations indicate that the effect of the crack length distribution is minor in term of the macroscopic behavior of the cracked body.

Prediction of the Fatigue Life of the Vibrational Sieve Supporting Beam

2017 ◽  
Vol 755 ◽  
pp. 274-278
Author(s):  
Jelena M. Djoković ◽  
Ružica R. Nikolić ◽  
Jan Bujnak
Keyword(s):  
Fatigue Life ◽  
Crack Length ◽  
Crack Propagation Rate ◽  
Working Life ◽  
Propagation Rate ◽  
Initial Crack ◽  
Initial Crack Length ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Remaining Fatigue Life

Vibrational sieves are exposed to exceptionally high cyclic loading during their working life and that is the reason why the special attention should be paid to estimates of the fatigue life of their structural elements, as well as to design with respect to fatigue fracture. Any change in the design appearance of the structural component must be carefully analyzed, since even the rearrangement of the components' elements layout, with keeping all the sizes constant, can cause serious consequences to the particular component's fatigue life. The research subject considered in this paper is the remaining fatigue life of the carrying beam, as well as the suggestions for improving the working life of the vibrational sieve. The Paris' law was used for estimates of the average crack propagation rate. From the presented diagram of the initial crack length versus the remaining working life one could see that the fatigue life decreases with the crack length increase. When the initial crack length reaches a value a little less than a half of the critical crack length, the remaining fatigue life starts to drop abruptly.

Characterization of fractures in shallow granite from the modeling of the anisotropy and attenuation of seismic waves

1999 ◽  
Vol 89 (3) ◽  
pp. 706-717 ◽  
Author(s):  
Sylvie Kelner ◽  
Michel Bouchon ◽  
Olivier Coutant
Keyword(s):  
Numerical Simulations ◽  
Crack Length ◽  
Seismic Waves ◽  
Seismic Anisotropy ◽  
Length Distribution ◽  
Integral Equation Method ◽  
Boundary Integral ◽  
Fractured Media ◽  
S Wave ◽  
P And Sv Waves

Abstract We try to characterize the fracturing of the anisotropic shallow granite (<250 m) present at Garner Valley, southern California. The shear-wave splitting observed on a downhole seismic array installed there (Archuleta et al., 1992) is modeled by performing numerical simulations of propagation of P and SV waves in 2D fractured media. The calculations are performed using a boundary integral equation method, which takes into account multiple scattering and full crack diffraction. The value of the time delay measured at Garner Valley between the fast S wave and the slow S wave is well reproduced for different models of fractured media. In order to differentiate between these models, we also measure and calculate the attenuation of the transmitted S waves. From the comparison between the observations and the numerical simulations, we conclude and infer the following: (1) The presence of fractures in granite explains the seismic anisotropy and attenuation observed at Garner Valley. (2) The cracks and fractures are nearly vertical and are oriented in a north-south direction. (3) There is no characteristic crack length, but rather, the crack length distribution seems to be fractal. (4) The density of fractures present in the shallow granite at Garner Valley is about 10−4 representing the total volume of the fractures over the total volume of the fractured zone.

A crack theory-based bonded particle model for rock particles considering size effect on crushing strength

2021 ◽  
Vol 11 (4) ◽  
pp. 1-38
Author(s):  
M.-j. Zhou
Keyword(s):  
Size Effect ◽  
Crack Length ◽  
Crack Density ◽  
Length Distribution ◽  
Particle Model ◽  
Crushing Strength ◽  
Bonded Particle Model ◽  
Proposed Model ◽  
Maximum Crack ◽  
Reasonable Prediction

Particle breakage shows significant effect on the macroscopic behavior of rock materials, and the discrete element method is a powerful tool to investigate the relationship between micro fracture and macro deformation and strength. In this study, the concept of crack is introduced into the bonded particle model (BPM) to simulate the breakage behaviour of rockfill materials, with randomly placed weak bonds representing cracks. Different from traditional BPM, the number, position and strength of the weak bonds are directly related to the number, position and length of cracks. With a reasonable length distribution of cracks, the proposed model can successfully reflect both the crushing strength variation and size effects. A set of crack parameters including the crack density, minimum crack length, maximum crack length and fractal dimension, are suggested. The crushing characteristics of realistic rockfill particles with two typical shapes are simulated quantitatively and verified with test data. It is found that the proposed model with suggested crack parameters can give reasonable prediction on the Weibull's modulus and size effect of rockfill particles.

Reliability of Steam Generator Tubes With Axial Cracks

1996 ◽  
Vol 118 (4) ◽  
pp. 441-446 ◽  
Author(s):  
L. Cizelj ◽  
B. Mavko ◽  
P. Vencelj
Keyword(s):  
Crack Length ◽  
Steam Generator ◽  
Nuclear Power ◽  
Length Distribution ◽  
Strong Suppression ◽  
Human Errors ◽  
Suppression Effect ◽  
Nondestructive Examination ◽  
Examination Techniques ◽  
Using Data

An approach for estimating the failure probability of tubes containing through-wall axial cracks has already been proposed by the authors. It is based on probabilistic fracture mechanics and accounts for scatter in tube geometry and material properties, scatter in residual and operational stresses responsible for crack propagation, and characteristics of nondestructive examination and plugging procedures (e.g., detection probability, sizing accuracy, human errors). Results of preliminary tests demonstrated wide applicability of this approach and triggered some improvements. The additions to the model are extensively discussed in this paper. Capabilities are demonstrated by results of analysis of steam generator no. 1 in Slovenian nuclear power plant located in Krsˇko after the 1992 inspection and plugging campaign. First, the number of cracked tubes and the crack length distribution were estimated using data obtained by the 100-percent motorized pancake coil inspection. The inspection and plugging activities were simulated in the second step to estimate the efficiency of maintenance in terms of single and multiple-tube rupture probabilities. They were calculated as a function of maximum allowable crack length. The importance of human errors and some limitations of present nondestructive examination techniques were identified. The traditional wall thickness and crack-length-based plugging criteria are compared. The crack-length-based criterion is shown to be more efficient and more safe, especially because of strong suppression effect on probability of multiple-tube rupture. The results are considered to be important for safety and maintenance of existing plants and for further research.

Influence of crack length and grain boundaries on the propagation rate of short cracks in austenitic stainless steel

2012 ◽  
Vol 67 (7-8) ◽  
pp. 677-680 ◽  
Author(s):  
M. Scharnweber ◽  
W. Tirschler ◽  
V. Mikulich ◽  
S. Jacob ◽  
C.-G. Oertel ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Crack Length ◽  
Grain Boundaries ◽  
Propagation Rate ◽  
Short Cracks

Interconnect Limits on Gigascale Integration (GSI)

1997 ◽  
Vol 473 ◽  
Author(s):  
J. A. Davis ◽  
J. D. Meindl
Keyword(s):  
Response Time ◽  
Length Distribution ◽  
Path Model ◽  
System Level ◽  
Wire Length ◽  
Clock Frequency ◽  
Gigascale Integration ◽  
Logic Network ◽  
Binary Switching ◽  
Quantitative Definition

ABSTRACTOpportunities for Gigascale Integration (GSI) are governed by a hierarchy of physical limits. The levels of this hierarchy have been codified as: 1) fundamental, 2) material, 3) device, 4) circuit and 5) system. Many key limits at all levels of the hierarchy can be displayed in the power, P, versus delay, td, plane and the reciprocal length squared, L-2, versus response time, τ, plane. Power, P, is the average power transfer during a binary switching transition and delay, td, is the time required for the transition. Length, L, is the distance traversed by an interconnect that joins two nodes on a chip and response time, τ, characterizes the corresponding interconnect circuit. At the system level of the hierarchy, quantitative definition of both the P versus td and the L-2 versus τ displays requires an estimate of the complete stochastic wiring distribution of a chip.Based on Rent's Rule, a well known empirical relationship between the number of signal input/output terminals on a block of logic and the number of gate circuits with the block, a rigorous derivation of a new complete stochastic wire length distribution for an on-chip random logic network is described. This distribution is compared to actual data for modern microprocessors and to previously described distributions. A methodology for estimating the complete wire length distribution for future GSI products is proposed. The new distribution is then used to enhance the critical path model that determines the maximum clock frequency of a chip; to derive a preliminary power dissipation model for a random logic network; and, to define an optimal architecture of a multilevel interconnect network that minimizes overall chip size. In essence, a new complete stochastic wiring distribution provides a generic basis for maximizing the value obtained from a multilevel interconnect technology.

Calculating Energy Release Rate as a Function of Crack Length Using a Multiple-Step Crack Closure Technique in Tire Finite Element Models

2018 ◽  
Vol 46 (3) ◽  
pp. 130-152
Author(s):  
Dennis S. Kelliher
Keyword(s):  
Finite Element ◽  
Energy Release Rate ◽  
Crack Length ◽  
Energy Release ◽  
Crack Closure ◽  
Release Rate ◽  
Fatigue Behavior ◽  
Three Dimensions ◽  
Quantitative Prediction ◽  
Closure Technique

ABSTRACT When performing predictive durability analyses on tires using finite element methods, it is generally recognized that energy release rate (ERR) is the best measure by which to characterize the fatigue behavior of rubber. By addressing actual cracks in a simulation geometry, ERR provides a more appropriate durability criterion than the strain energy density (SED) of geometries without cracks. If determined as a function of crack length and loading history, and augmented with material crack growth properties, ERR allows for a quantitative prediction of fatigue life. Complications arise, however, from extra steps required to implement the calculation of ERR within the analysis process. This article presents an overview and some details of a method to perform such analyses. The method involves a preprocessing step that automates the creation of a ribbon crack within an axisymmetric-geometry finite element model at a predetermined location. After inflating and expanding to three dimensions to fully load the tire against a surface, full ribbon sections of the crack are then incrementally closed through multiple solution steps, finally achieving complete closure. A postprocessing step is developed to determine ERR as a function of crack length from this enforced crack closure technique. This includes an innovative approach to calculating ERR as the crack length approaches zero.

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