The physics of fatigue crack initiation
TL;DR: In this paper, the authors focus on experimental observations of strain localization and the theory and numerical analysis of both slip irreversibilities and low energy configuration defect structures, which are the early signs of damage during cyclic loading.
About: This article is published in International Journal of Fatigue.The article was published on 2013-12-01. It has received 495 citations till now. The article focuses on the topics: Crack closure & Slip (materials science).
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TL;DR: In this article, the authors present a comprehensive, critical review of the mechanical behavior of high-entropy alloys and some closely related topics, including thermodynamics and kinetics.
379 citations
TL;DR: In this article, a gradient nanostructured (GNS) surface layer was formed on AISI 316L stainless steel and the mean grain size is ∼30nm in the topmost surface layer and increases with depth.
363 citations
TL;DR: In this paper, the authors review the literature on the influential microstructural attributes on fatigue performance of additive manufacturing (AM) parts with a focus on generated defects, including defect-based, microstructure-sensitive, and multiscale models.
309 citations
TL;DR: These findings demonstrate that microtubules are ductile materials with self-healing properties, that their dynamics does not exclusively occur at their ends, and that their lattice plasticity enables the microtubule's adaptation to mechanical stresses.
Abstract: Microtubules--which define the shape of axons, cilia and flagella, and provide tracks for intracellular transport--can be highly bent by intracellular forces, and microtubule structure and stiffness are thought to be affected by physical constraints. Yet how microtubules tolerate the vast forces exerted on them remains unknown. Here, by using a microfluidic device, we show that microtubule stiffness decreases incrementally with each cycle of bending and release. Similar to other cases of material fatigue, the concentration of mechanical stresses on pre-existing defects in the microtubule lattice is responsible for the generation of more extensive damage, which further decreases microtubule stiffness. Strikingly, damaged microtubules were able to incorporate new tubulin dimers into their lattice and recover their initial stiffness. Our findings demonstrate that microtubules are ductile materials with self-healing properties, that their dynamics does not exclusively occur at their ends, and that their lattice plasticity enables the microtubules' adaptation to mechanical stresses.
231 citations
TL;DR: In this article, a multistage grain scale approach to microstructure-sensitive fatigue crack formation and growth is presented which uses Fatigue Indicator Parameters (FIPs) to correlate these processes.
196 citations
References
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TL;DR: In this article, the authors investigated the effect of surface scratches on the mechanical strength of solids, and some general conclusions were reached which appear to have a direct bearing on the problem of rupture, from an engineering standpoint, and also on the larger question of the nature of intermolecular cohesion.
Abstract: In the course of an investigation of the effect of surface scratches on the mechanical strength of solids, some general conclusions were reached which appear to have a direct bearing on the problem of rupture, from an engineering standpoint, and also on the larger question of the nature of intermolecular cohesion. The original object of the work, which was carried out at the Royal Aircraft Establishment, was the discovery of the effect of surface treatment—such as, for instance, filing, grinding or polishing—on the strength of metallic machine parts subjected to alternating or repeated loads. In the case of steel, and some other metals in common use, the results of fatigue tests indicated that the range of alternating stress which could be permanently sustained by the material was smaller than the range within which it was sensibly elastic, after being subjected to a great number of reversals. Hence it was inferred that the safe range of loading of a part, having a scratched or grooved surface of a given type, should be capable of estimation with the help of one of the two hypotheses of rupture commonly used for solids which are elastic to fracture. According to these hypotheses rupture may be expected if (a) the maximum tensile stress, ( b ) the maximum extension, exceeds a certain critical value. Moreover, as the behaviour of the materials under consideration, within the safe range of alternating stress, shows very little departure from Hooke’s law, it was thought that the necessary stress and strain calculations could be performed by means of the mathematical theory of elasticity.
10,162 citations
"The physics of fatigue crack initia..." refers result in this paper
...Hence, the failure criterion is an energy balance with respect to plastic deformation, which is in accordance to other well-known energy balances for describing material behavior, such as Griffith’s fracture criterion [131] or Rice and Thomson’s brittle versus ductile behavior [132]....
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Book•
01 Jan 1980
TL;DR: In this paper, the authors present methods proven successful in practice, such as safe-life, fail-safe, forecasting of service reliability, monitoring, and inspection; macroscopic and microscopic aspects of fatigue behavior; principles for determining fatigue crack growth and final fracture; scatter of data and statistical methods; environmental factors; and fatigue of joints and compounds.
Abstract: Presents methods proven successful in practice. Covers design procedures, such as safe-life, fail-safe, forecasting of service reliability, monitoring, and inspection; macroscopic and microscopic aspects of fatigue behavior; principles for determining fatigue crack growth and final fracture; scatter of data and statistical methods; environmental factors; and fatigue of joints and compounds. Contains design do's and don'ts and example problems.
1,837 citations
"The physics of fatigue crack initia..." refers background in this paper
...The relative cost of these failures constitutes approximately 4% of the gross national product of the US [1]....
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...The importance of fatigue is evident; although exact numbers are not available, it is expected that at least half of all mechanical failures are due to fatigue [1]....
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TL;DR: In this paper, a superimposed dislocation network is proposed for the cubic system, which is a natural extension of previous dislocation models and models based on coincidence relationships, and explains many of the observed properties of grain boundaries.
1,665 citations
TL;DR: In this article, a necessary criterion for brittle fracture in crystals is established, in terms of the spontaneous emission of dislocations from an atomically sharp cleavage crack, and the stability of a sharp crack against emission of a blunting dislocation for a number of crystals and crystal types in two dimensions and the energy to form a stable loop of dislocation from the crack tip in three dimensions.
Abstract: A necessary criterion for brittle fracture in crystals is established, in terms of the spontaneous emission of dislocations from an atomically sharp cleavage crack. We have calculated the stability of a sharp crack against emission of a blunting dislocation for a number of crystals and crystal types in two dimensions and the energy to form a stable loop of dislocation from the crack tip in three dimensions. We find that contrary to previous expectations, an atomically sharp cleavage crack is stable in a wide range of crystal types, but that in the face centred cubic metals investigated, blunting reactions occur spontaneously. Of the body centred metals investigated, iron is an intermediate case between the brittle and ductile cases, and the ionic and covalent crystals investigated are all stable against dislocation emission. Qualitatively, we find that crystals whose dislocations have wide cores, and small values of the parameter μb/γ (μb/γ⋦7·5 to 10) are ductile while crystals with narrow cores ...
1,413 citations
"The physics of fatigue crack initia..." refers result in this paper
...Hence, the failure criterion is an energy balance with respect to plastic deformation, which is in accordance to other well-known energy balances for describing material behavior, such as Griffith’s fracture criterion [131] or Rice and Thomson’s brittle versus ductile behavior [132]....
[...]
TL;DR: In this article, a simple model for single-slip and multiple-slink deformation is proposed, in which the crystal is considered as a composite consisting of hard dislocation walls of high local dislocation density which are separated by soft regions of low local dislocations density.
1,001 citations