Crack-Tip Shielding in Metal-Matrix Composites: Modelling Of Crack Bridging by Uncracked Ligaments

AbstractAs part of an investigation into the micro-mechanisms of crack-tip shielding associated with the growth of fatigue cracks in metal-matrix composites, simple models are developed for the role of crack bridging in high-strength aluminum alloys reinforced with SiC particulate (AI/SiCp). Based on experimental observations of crack growth, crack-tip shielding and crack-path morphology in these alloys, the bridges are found to be associated with uncracked ligaments in the wake of the crack tip, and are modelled in terms of approaches based on a critical crack-opening displacement or critical tensile strain in the ligament.

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Test for Crack Opening Displacement of Steel Fiber Reinforced Concrete under Three-Point Bending

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.36.157 ◽

2010 ◽

Vol 36 ◽

pp. 157-161 ◽

Cited By ~ 2

Author(s):

Tin Gyi Zhang ◽

Yuan Bao Leng ◽

Dan Ying Gao

Keyword(s):

Crack Opening Displacement ◽

Crack Opening ◽

Mouth Opening ◽

Crack Tip ◽

Crack Mouth Opening Displacement ◽

Crack Tip Opening Displacement ◽

Opening Displacement ◽

Critical Crack ◽

Critical Crack Opening ◽

Crack Tip Opening

Based on the principle of electrical measurement method, the clip gauge was made to measure the crack opening displacement (COD).Through the three-point bending test on the specimens of steel fiber reinforced high strength concrete (SFHSC), the effect of the fiber volume fraction (ρf) upon the critical crack opening displacement (the critical crack tip opening displacement and the critical crack mouth opening displacement) was studied. The result shows that the effect of ρf on mouth-tip ratio (the ratio of critical crack mouth opening displacement to critical crack tip opening displacement) can reflect its effect upon the critical crack opening displacement. According to the geometrical relationship between the initial crack length and the critical crack opening displacement，calculation method for the initial crack length was proposed. Based on the test result, the formula was established for calculating the critical crack tip opening displacement.

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Investigation of crack-tip plasticity in high volume fraction particulate metal matrix composites

Engineering Fracture Mechanics ◽

10.1016/j.engfracmech.2004.01.006 ◽

2004 ◽

Vol 71 (16-17) ◽

pp. 2385-2406 ◽

Cited By ~ 26

Author(s):

A. Miserez ◽

A. Rossoll ◽

A. Mortensen

Keyword(s):

Metal Matrix Composites ◽

Metal Matrix ◽

Volume Fraction ◽

Crack Tip ◽

High Volume ◽

High Volume Fraction ◽

Matrix Composites ◽

Particulate Metal ◽

Crack Tip Plasticity

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J-Integral and Crack Opening Displacement as Crack Initiation Criteria in Rubber

Rubber Chemistry and Technology ◽

10.5254/1.3538234 ◽

1986 ◽

Vol 59 (5) ◽

pp. 787-799 ◽

Cited By ~ 1

Author(s):

R. F. Lee ◽

J. A. Donovan

Keyword(s):

Crack Initiation ◽

Carbon Black ◽

Crack Growth ◽

Crack Opening ◽

Crack Tip ◽

J Integral ◽

Carbon Black Content ◽

Opening Displacement ◽

Critical Crack ◽

Growth Initiation

Abstract 1. Evaluation of ∫σdδ where σ is the net section stress and δ is the deformed crack tip diameter requires only one specimen to characterize the initiation of crack growth in unfilled and carbon-black-filled NR. 2. ∫σdδ is equal to one half of the J-integral for crack growth initiation, which is identical to the Thomas tearing energy for a blunt notch. 3. The critical J-integral for crack initiation increases linearly with carbon black content. 4. The critical crack tip radius for crack initiation is independent of carbon black content, and the required crack tip region stress increases linearly with carbon black content.

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In-Situ NDE Monitoring of Crack Bridging in Ceramic Composites via Crack Opening Displacement

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; General ◽

10.1115/94-gt-444 ◽

1994 ◽

Cited By ~ 1

Author(s):

Abhisak Chulya ◽

John P. Gyekenyesi

Keyword(s):

Crack Opening ◽

Ceramic Matrix Composites ◽

Ceramic Composites ◽

In Situ Observation ◽

Matrix Composites ◽

Opening Displacement ◽

Crack Bridging ◽

Interferometric Technique ◽

Fiber Bridging

A study of crack bridging in long-fiber reinforced ceramic matrix composites (CMC) is the main focus of this paper. The in-situ observation using NDE techniques reveals that 1D SiC/CAS CMCs show only partial fiber bridging behavior while 2D SiC/SiC CMCs possess an excellent bridging mechanism. Laser interferometric technique was successfully applied to measure crack opening displacements (COD) in the notched specimens under four-point flexural loading. The onset of precracking and the effects of fiber bridging were also detected by in-situ optical microscopy and acoustic emission techniques. The applied load-COD relations were shown and on the basis of these results, the bridging stiffness parameter can be determined via the fracture mechanics formulation proposed by Cox and Marshall.

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Controlled Initiation of Short Fatigue Cracks in 316L Steel

Volume 6: Materials and Fabrication ◽

10.1115/pvp2005-71298 ◽

2005 ◽

Author(s):

D. Stefanescu ◽

J. Marrow ◽

M. Preuss ◽

A. Sherry

Keyword(s):

Experimental Study ◽

Stainless Steel ◽

Crack Opening Displacement ◽

Crack Nucleation ◽

Fatigue Cracks ◽

Crack Opening ◽

Crack Tip ◽

Image Correlation ◽

Opening Displacement ◽

R Ratio

Validation of models for short crack behavior requires accurate measurement of crack opening displacement and crack tip strain fields. Development of reliable measurement procedures, using new techniques such as Image Correlation (IC), requires specimens containing cracks with a well defined geometry. In this paper, results of an experimental study concerning controlled initiation of short fatigue cracks at positive R-ratio in laboratory specimens made from 316L stainless steel are presented. Experimental techniques, including hardness testing and X-ray diffraction were employed in order to investigate the effect of surface preparation on the surface mechanical properties and residual stresses. Crack nucleation is difficult in smooth specimens of 316L austenitic stainless steel at positive R-ratio due to the high fatigue limit and low tensile strength. Specimens with a thin ligament were therefore developed to enable nucleation of a single short fatigue crack. An experimental study of the crack growth aspect ratio evolution was then carried out using a beach marking technique. The technique described in this paper enables single short fatigue cracks of well defined geometry to be nucleated under tensile cyclic loading. Stress corrosion cracks can be developed using the same specimen geometry. Miniature tensile specimens can then be extracted to perform in-situ measurements of the crack opening displacement and crack tip strain field by Image Correlation from Scanning Electron Microscopy observations.

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