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Karel Obrtlík

Other affiliations: Technical University of Ostrava
Bio: Karel Obrtlík is an academic researcher from Academy of Sciences of the Czech Republic. The author has contributed to research in topics: Superalloy & Inconel. The author has an hindex of 20, co-authored 82 publications receiving 1591 citations. Previous affiliations of Karel Obrtlík include Technical University of Ostrava.


Papers
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TL;DR: A comprehensive inventory of microscopic techniques used for this study is tabulated chronologically with emphasis to their applicability to polycrystals as mentioned in this paper, and the most relevant experimental characteristics concerning surface relief evolution, namely the form of extrusions and intrusions in single and polycrystalline materials, are surveyed.
Abstract: Current state and historical progress in experimental and theoretical studies of surface relief appertaining to persistent slip bands (PSBs) and leading to fatigue crack initiation in cyclically deformed metals is presented as a thorough critical overview. A comprehensive inventory of microscopic techniques used for this study is tabulated chronologically with emphasis to their applicability to polycrystals. The most relevant experimental characteristics concerning surface relief evolution, namely the form of extrusions and intrusions in single- and polycrystalline materials, are surveyed. Theoretical models and computational simulations of extrusion and intrusion formation and fatigue crack initiation are critically reviewed. †In 2003, it was 100 years since J.A. Ewing and J.C.W. Humfrey first documented the nature of early surface fatigue damage in Swedish iron in their paper The Fracture of Metals under Repeated Alternations of Stress published in the journal Philosophical Transactions of the Royal Soc...

165 citations

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TL;DR: In this paper, surface relief is formed mostly by ribbon-like extrusions whose height in a grain was found to be proportional to the thickness of the corresponding persistent slip bands.

134 citations

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TL;DR: In this paper, the surface relief evolution at emerging persistent slip bands (PSBs) in individual grains of polycrystalline 316L stainless steel cycled with constant plastic strain amplitude was studied.
Abstract: Atomic force microscopy was applied to study the surface relief evolution at emerging persistent slip bands (PSBs) in individual grains of polycrystalline 316L stainless steel cycled with constant plastic strain amplitude. Quantitative data on the changes of the surface topography of persistent slip markings (PSMs) and on the kinetics of extrusion growth during the fatigue life of smooth specimens were obtained. The extrusion height can be assessed by a direct observation of the metal surface and the intrusion depth using the plastic replica technique. The first PSMs appear after the initial hardening (0.1–0.25% of Nf). PSBs can be active in the whole period of fatigue life in grains in which no cracks develop. The initial rapid growth of extrusions is followed by a period of stable linear growth up to the end of the fatigue life. The width of extrusions, corresponding to the thickness of the emerging PSBs quickly stabilizes and remains constant during the whole fatigue life. The experimental results are discussed in terms of recent vacancy models of surface relief evolution.

114 citations

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TL;DR: In this article, the spatial arrangement of dislocations in the grains was determined using the technique of oriented foils, characteristic of amplitudes corresponding to three regimes of cyclic stress-strain curves, and their proportions as a function of the plastic strain amplitude and the number of cycles, were evaluated.
Abstract: Dislocation structures in two heats of 316L austenitic stainless steels, cyclically strained at room temperature with constant plastic strain amplitude over a wide interval, were studied. The spatial arrangement of dislocations in the grains was determined using the technique of oriented foils. The main types of dislocation structures, characteristic of amplitudes corresponding to three regimes of cyclic stress-strain curves, and their proportions as a function of the plastic strain amplitude and the number of cycles, were evaluated. In each regime of cyclic stress-strain curve a dominant dislocation structure was found: planar dislocation arrays arranged in sheets in regime I ( ϵ ap −4 ), imperfect vein structure with persistent slip bands in the plateau regime II (1 × 10 −4 ϵ ap −3 ), and cells and wall structures in regime III ( ϵ ap > 1 × 10 −3 ).

110 citations

Journal ArticleDOI
TL;DR: In this paper, the true surface relief corresponding to persistent slip markings emerging from persistent slip bands on fatigued polycrystalline austenitic and ferritic stainless steels was found.

97 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Reference EntryDOI
31 Oct 2001
TL;DR: The American Society for Testing and Materials (ASTM) as mentioned in this paper is an independent organization devoted to the development of standards for testing and materials, and is a member of IEEE 802.11.
Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

3,792 citations

Journal ArticleDOI
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.

495 citations

Journal ArticleDOI
TL;DR: In this article, microstructure-sensitive fatigue modeling is proposed for Ni-base superalloys, gear steels, and α-β Ti alloys, with focus on the individual grain scale as the minimum length scale of heterogeneity.

447 citations

Journal ArticleDOI
TL;DR: In this paper, the role of microstructural features such as grain size, texture, porosity, non-metallic inclusion in the fatigue crack initiation process and the manners by which these micro-structural effects affect the shape of the stress-life curves are examined.

363 citations