Fatigue Crack Propagation Related to a Dislocation Distribution

Mura, T.; Vilmann, C. R.

doi:10.1007/978-94-011-7520-3_8

Cited by 3 publications

(3 citation statements)

References 12 publications

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“…The Burgers vector of as is tangential to the line of discontinuity (see Fig. The application of this result to fatigue has been considered by Mura and Vilmann (1981). in the left-hand fan-shaped region.…”

Section: Plane Strain Problemsmentioning

confidence: 97%

Micromechanics of defects in solids

Mura¹,

Barnett

1987

Mechanics of Elastic and Inelastic Solids

3,030

1,372

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PrefaceThis book stems from a course on Micromechanics that I started about fifteen years ago at Northwestern University. At that time, micromechanics was a rather unfamiliar subject. Although I repeated the course every year, I was never convinced that my notes have quite developed into a final manuscript because new topics emerged constantly requiring revisions, and additions. I finally came to realize that if this is continued, then I will never complete the book to my total satisfaction. Meanwhile, T. Mori and I had coauthored a book in Japanese, entitled Micromechanics, published by Baifu-kan, Tokyo, in 1975. It received an extremely favorable response from students and researchers in Japan. This encouraged me to go ahead and publish my course notes in their latest version, as this book, which contains further development of the subject and is more comprehensive than the one published in Japanese.Micromechanics encompasses mechanics related to microstructures of materials. The method employed is a continuum theory of elasticity yet its applications cover a broad area relating to the mechanical behavior of materials: plasticity, fracture and fatigue, constitutive equations, composite materials, polycrystals, etc. These subjects are treated in this book by means of a powerful and unified method which is called the 'eigenstrain method.' In particular, problems relating to inclusions and dislocations are most effectively analyzed by this method, and therefore, special emphasis is placed on these topics. When this book is used as a text for a graduate course, Sections 3, 11, and 22 should be emphasized.

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Section: Plane Strain Problemsmentioning

confidence: 97%

Micromechanics of defects in solids

Mura¹,

Barnett

1987

Mechanics of Elastic and Inelastic Solids

3,030

1,372

View full text Add to dashboard Cite

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“…The dislocation generated by fatigue stress easily crosses the grain boundary. The concentration effect of dislocations and the degree of stress concentration is reduced, which is beneficial to slow the fatigue crack initiation [ 19 ]. When the dislocation passes through the PFZ, the wider the PFZ is, the more the stress get relaxed, and the more difficult for the fatigue cracks to initiate.…”

Section: Discussionmentioning

confidence: 99%

“…Most of the precipitates in the under-aged alloy can be repeatedly sheared by the fatigue crack tip dislocations. This mechanism makes the fatigue crack path highly serrated and tortuous [ 19 , 20 ]. Reasons such as reversible dislocation motion, the plastically induced crack closure (PICC) and RICC make fatigue crack propagation for under-aged alloy very slow [ 21 ].…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Precipitate Microstructure Affecting Fatigue Behavior of 7020 Aluminum Alloy

Shan

Liu

et al. 2020

Materials

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The effect of different precipitate microstructures obtained by different heat treatments on fatigue behavior of 7020 aluminum alloy was investigated. The fine Guinier Preston I (GPI) zones in the under-aged alloy can be repeatedly sheared by dislocations produced in cyclic loading, making the fatigue crack initiate difficultly and fatigue crack path propagate tortuously. Fatigue strength and fatigue crack propagation resistance of the alloy with shearable precipitates are much higher than those of the alloy with unshearable precipitates. The peak-aged alloy with continuous grain boundary precipitate (GBP) and narrow precipitate free zone (PFZ) is prone to initiate fatigue cracks and reduce fatigue strength. With the growth of unshearable precipitates, the fatigue strength of the alloy firstly increases and then decreases. Precipitates with moderate size in the over-aged alloy improve the roughness-induced crack closure (RICC) effect. Soft matrix with appropriate width between the precipitates can promote the slip reversibility and relax the crack tip stress. The fatigue strength of the moderately over-aged alloy reaches to 122.1 MPa at 107 cycles of loading, and the fatigue crack growth rate (FCGR) is 35.6% slower than that of the peak-aged alloy at ΔK of 10 MPa·m1/2.

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Quantitative Measurement of Energy Associated with a Moving Fatigue Crack

Fine¹,

Davidson

1983

Fatigue Mechanisms: Advances in Quantitative Measurement of Physical Damage

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Energy must be supplied to accomplish the processes which occur in the plastic zone ahead of the crack during fatigue crack extension. This energy has been measured (1) by using foil strain gages (Ikeda, Izumi, and Fine), (2) from electron-channeling patterns (Davidson and Lankford), (3) by stereoimaging (Davidson and Lankford), and (4) from calorimetric measurement of the heat generated during crack propagation (Gross and Weertman). The experimental results to date are presented and discussed. Both the hysteretic and permanent plastic work have been measured by strain pages. The permanent plastic work and the stored energy from cyclic plastic work are negligible. The work done numerically equals the heat evolved. The crack propagation rate data fit an equation dC/dN = AΔK4/μσ'yU, where A is a universal constant, µ is the shear modulus, σ'y is the cyclic yield stress, and U is the energy per unit area of fatigue crack. The latter is a function of ΔK except when the exponent in the Paris equation is 4.

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Fatigue Crack Propagation Related to a Dislocation Distribution

Cited by 3 publications

References 12 publications

Micromechanics of defects in solids

Micromechanics of defects in solids

Mechanism of Precipitate Microstructure Affecting Fatigue Behavior of 7020 Aluminum Alloy

Quantitative Measurement of Energy Associated with a Moving Fatigue Crack

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