Physical and Phenomenological Model with Non-Linearity in Ductile Fracture and Fatigue Crack Growth

Yokobori, Takeo; Yokobori, A. T.

doi:10.1007/978-3-642-81582-9_40

Cited by 3 publications

(13 citation statements)

References 9 publications

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“…2.1. Model, Basic Equation and Method of Analysis [2,9,10] Plastic deformation is caused by dislocation group motion emitted from a stressed source. It closely relates to plastic yielding and fatigue crack growth dominated by discrete dislocations emitted from a stressed source near a crack tip.…”

Section: Dislocation Groups Dynamics Aimed For Applications To Problems Of Yielding Creep and Fatigue [2910]mentioning

confidence: 99%

“…When the effective stress exerted on dislocation source (x = 0.0) takes the source activation stress, the new dislocation is originated at x = 0.0, and these processes are iterated. Equations (2) and (1) were solved by the Runge-Kutta Merson method. The effective stress exerted on a dislocation source is given by Equation (4).…”

Section: Dislocation Groups Dynamics Aimed For Applications To Problems Of Yielding Creep and Fatigue [2910]mentioning

confidence: 99%

“…The latter closely relates to connect problems of the strength and fracture of materials with the macro scale [2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

“…This article is related to the fracture of materials. For this case, the numerical results of the number of moving dislocations emitted from a stressed source and local stress concentration caused by a dislocation pile-up were necessary to be formulated as an analytical function of applied stress or stress rate, temperature, and material constants [2,3].…”

Section: Introductionmentioning

confidence: 99%

“…Yielding phenomena such as stress rate and grain size dependence of yield stress and delayed time of yielding were especially clarified as a holistic phenomenon composed of sequential processes of dislocation release from a solute atom [7,8], dislocation group moving [6], and stress concentration by a pile-up at the grain boundary [2][3][4].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Holistic Approach on the Research of Yielding, Creep and Fatigue Crack Growth Rate of Metals Based on Simplified Model of Dislocation Group Dynamics

Yokobori

2020

Metals

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The simplified model of numerical analyses of discrete dislocation motion and emissionfrom a stressed source was applied to predict the yield stress, dislocation creep, and fatigue crackgrowth rate of metals dominated by dislocation motion. The results obtained by these numericalanalyses enabled us to link various dynamical effects on the yield stress, dislocation creep, andfatigue crack growth rate with the experimental results of macroscopic phenomena, as well as tolink them with theoretical results obtained by the concept of static, continuously distributedinfinitesimal dislocations for the equilibrium state under low strain or stress rate conditions. Thiswill be useful to holistic research approaches with concern for time and space scales, that is, in atime scale ranging from results under high strain rate condition to those under static or low strainrate condition, and in a space scale ranging from meso-scale to macro-scale mechanics. Theoriginality of results obtained by these analyses were found by deriving the analytical formulationsof number of dislocation emitted from a stressed source and a local dynamic stress intensity factorat the pile-up site of dislocations as a function of applied stress or stress rate and temperaturematerial constants. This enabled us to develop the predictive law of yield stress, creep deformationrate, and fatigue crack growth rate of metals dominated by dislocation motion. Especially, yieldingphenomena such as the stress rate and grain size dependence of yield stress and the delayed timeof yielding were clarified as a holistic phenomenon composed of sequential processes of dislocationrelease from a solute atom, dislocation group moving, and stress concentration by pile-up at thegrain boundary.

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Section: Dislocation Groups Dynamics Aimed For Applications To Problems Of Yielding Creep and Fatigue [2910]mentioning

confidence: 99%

Section: Dislocation Groups Dynamics Aimed For Applications To Problems Of Yielding Creep and Fatigue [2910]mentioning

confidence: 99%

“…The latter closely relates to connect problems of the strength and fracture of materials with the macro scale [2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Holistic Approach on the Research of Yielding, Creep and Fatigue Crack Growth Rate of Metals Based on Simplified Model of Dislocation Group Dynamics

Yokobori

2020

Metals

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Stress Rate and Grain Size Dependence of Dynamic Stress Intensity Factor by Dynamical Piling-up of Dislocations Emitted

Yokobori

Nishi

1987

Macro- And Micro-Mechanics of High Velocity Deformation and Fracture

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Dislocation Emission and Dynamics Under the Stress Singularity at the Crack Tip and Its Application to the Dynamic Loading Effect on Fracture Toughness

Yokobori

Iwadate

Isogai

1994

Fracture Mechanics: Twenty-Fourth Volume

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In previous work, computer simulation of dislocation emission and motion was carried out considering the stress singularity near the crack tip. It was found that there is a region in which no dislocation exists along the slip plane near the stressed source, namely, a dislocation free zone (DFZ), and that there is an inverse pileup of dislocations against the tip of this DFZ. A formula was obtained correlating the maximum dislocation density with the DFZ length. Based on those results, an evaluation has now been attempted for fracture toughness within the brittle-ductile transition range of steel. The effect of dynamic loading on the fracture toughness and trigger point observed in the experimental results reported in the literature is explained.

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Physical and Phenomenological Model with Non-Linearity in Ductile Fracture and Fatigue Crack Growth

Cited by 3 publications

References 9 publications

Holistic Approach on the Research of Yielding, Creep and Fatigue Crack Growth Rate of Metals Based on Simplified Model of Dislocation Group Dynamics

Holistic Approach on the Research of Yielding, Creep and Fatigue Crack Growth Rate of Metals Based on Simplified Model of Dislocation Group Dynamics

Stress Rate and Grain Size Dependence of Dynamic Stress Intensity Factor by Dynamical Piling-up of Dislocations Emitted

Dislocation Emission and Dynamics Under the Stress Singularity at the Crack Tip and Its Application to the Dynamic Loading Effect on Fracture Toughness

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