Spatial Variability in Concrete: Nature, Structure, and Consequences

The failure process of concrete is a complex phenomenon in which the material inhomogeneities play an important role. Different ways of accounting for material disorder are commented on and examples are exhibited, showing the difficulties related to inhomogeneous material modeling. In a first part, results and limits via phenomenological probabilistic models (a probabilistic model of damage and a probabilistic numerical model of cracking) are pointed out. Then, results obtained on numerical simulations on lattices are studied. It is shown that the knowledge of the local disorder is a key factor for a better understanding of the global response (localization, size-effect, ...), even if these results can only be taken as qualitative ones. It appears that studies using numerical discrete models for concrete can lead to spurious results if the bias introduced by the discretization itself is not recognized and correctly accounted for. Finally it is shown with two examples (casted concrete and microcracked medium) how the structure of disorder can be identified and modelled. Some indications are given about the cases in which it seems useful to analyze the material at this micro-scale. The main interest seems to be their use for building phenomenological and material-related rules describing the response at a higher scale. The conclusion tries to separate the problems one has to treat in four main classes and to propose for each type of problem a better way to account for material disorder.

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Non Parametric Probabilistic Approach of Ice Load Peaks on Ship Hulls

Volume 6: Materials Technology; Polar and Arctic Sciences and Technology; Petroleum Technology Symposium ◽

10.1115/omae2012-83165 ◽

2012 ◽

Author(s):

Abdillah Suyuthi ◽

Bernt J. Leira ◽

Kaj Riska

Keyword(s):

Probabilistic Models ◽

Extreme Values ◽

Probabilistic Approach ◽

Initial Distribution ◽

Complex Phenomenon ◽

Short Term ◽

Ship Hulls ◽

Ice Load ◽

Non Parametric

Due to its complex phenomenon, ice-induced load process could not be physically possible to be modeled by a specific well established probabilistic model. Therefore, a non parametric approximate probabilistic approach should be performed based on the available data. This paper describes the procedure and also the extrapolation to get the short term and long term extreme values. Comparison with the classical approach, where the initial distribution of ice-induced load is assumed to be one of the well established probabilistic models, was made. The comparisons discussed in this paper were explored by using the same available data of full scale measurement on board a coastal guard vessel KV Svalbard during the winter 2007. There was a tendency that the non parametric approach produces more conservative results.

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Measures of Entropy to Characterize Fatigue Damage in Metallic Materials

Entropy ◽

10.3390/e21080804 ◽

2019 ◽

Vol 21 (8) ◽

pp. 804 ◽

Cited By ~ 9

Author(s):

Huisung Yun ◽

Mohammad Modarres

Keyword(s):

Statistical Mechanics ◽

Fatigue Damage ◽

Fatigue Failure ◽

Probabilistic Models ◽

Failure Process ◽

Second Law Of Thermodynamics ◽

Boltzmann Constant ◽

Metallic Materials ◽

Thermodynamic Entropy ◽

Macro Scale

This paper presents the entropic damage indicators for metallic material fatigue processes obtained from three associated energy dissipation sources. Since its inception, reliability engineering has employed statistical and probabilistic models to assess the reliability and integrity of components and systems. To supplement the traditional techniques, an empirically-based approach, called physics of failure (PoF), has recently become popular. The prerequisite for a PoF analysis is an understanding of the mechanics of the failure process. Entropy, the measure of disorder and uncertainty, introduced from the second law of thermodynamics, has emerged as a fundamental and promising metric to characterize all mechanistic degradation phenomena and their interactions. Entropy has already been used as a fundamental and scale-independent metric to predict damage and failure. In this paper, three entropic-based metrics are examined and demonstrated for application to fatigue damage. We collected experimental data on energy dissipations associated with fatigue damage, in the forms of mechanical, thermal, and acoustic emission (AE) energies, and estimated and correlated the corresponding entropy generations with the observed fatigue damages in metallic materials. Three entropic theorems—thermodynamics, information, and statistical mechanics—support approaches used to estimate the entropic-based fatigue damage. Classical thermodynamic entropy provided a reasonably constant level of entropic endurance to fatigue failure. Jeffreys divergence in statistical mechanics and AE information entropy also correlated well with fatigue damage. Finally, an extension of the relationship between thermodynamic entropy and Jeffreys divergence from molecular-scale to macro-scale applications in fatigue failure resulted in an empirically-based pseudo-Boltzmann constant equivalent to the Boltzmann constant.

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Fracture Mechanics of Fiber-Matrix Interfaces in Composites under Transverse Loading

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.577-578.433 ◽

2013 ◽

Vol 577-578 ◽

pp. 433-436

Author(s):

Christian Marotzke ◽

Titus Feldmann

Keyword(s):

Failure Process ◽

Unidirectional Composite ◽

Shear Loading ◽

Volume Element ◽

Finite Element Analyses ◽

Transverse Loading ◽

Fiber Volume ◽

Transverse Tension ◽

Key Factor ◽

Debonding Process

The Failure of the Interface between Fiber and Matrix under Transverse Loading is the Key Factor Controlling the Failure Process in Composite Materials. the Debonding Process of a Fiber within a Unidirectional Composite is Studied by Finite Element Analyses Using a Representative Volume Element. the Energy Release Rate is Calculated for Different Fiber Volume Fractions. Two Load Cases are Taken into Account, Pure Transverse Tension and Shear Loading.

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Study on the Catastrophic Evolution of Tianshan Road Slope under the Freeze-Thaw Cycles

Geofluids ◽

10.1155/2021/6128843 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Luqi Wang ◽

Yibing Zhang ◽

Jian Guo ◽

Qiang Ou ◽

Songlin Liu ◽

...

Keyword(s):

Rock Mass ◽

Failure Process ◽

Maximum Temperature ◽

Mechanism Analysis ◽

Long Distance ◽

Maximum Temperature Difference ◽

Rocky Slope ◽

Freeze Thaw ◽

Rock Fragments ◽

Key Factor

The maximum temperature difference of Tianshan Road can reach 77.4°C in a year. Under such complex mechanical environment, the mechanical properties of rock mass and structural planes will change significantly as the increase of freeze-thaw cycles (FTC). Consequently, the FTC has become a key factor in the instability and failure of rocky slopes along the Tianshan Road. In this paper, the progressive deformation of rocky slopes and sudden failure process after critical instability were studied through the FTC tests of rock mass and structural planes, discrete element method, and theoretical analysis. The results show that the structural planes and internal microcracks of the rock mass expand under the action of the FTC, causing a gradual decrease in the stability of the slope. The dynamic collapse of the rocky slope has a certain degree of randomness caused by the spatial distribution of structural planes and the interaction between the rock fragments. Due to the limitation of the slipping space and the tilt angle of the trailing edge of the slope, long-distance migration did not occur, and the in situ accumulation of the slope was obvious after failure. The analysis method in this paper can provide an important reference for guiding the catastrophe mechanism analysis and protection of engineering slopes in cold regions.

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Scanning electron microscopy of erythrophagocytosis by Entamoeba histolytica trophozoites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012480x ◽

1992 ◽

Vol 50 (1) ◽

pp. 880-881

Author(s):

Victor Tsutsumi ◽

Adolfo Martinez-Palomo ◽

Kyuichi Tanikawa

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Red Blood Cells ◽

Entamoeba Histolytica ◽

Causative Agent ◽

Blood Cells ◽

Protozoan Parasite ◽

Complex Phenomenon ◽

Great Capacity ◽

Scanning Electron

The protozoan parasite Entamoeba histolytica is the causative agent of amebiasis in man. The trophozoite or motile form is a highly dynamic and pleomorphic cell with a great capacity to destroy tissues. Moreover, the parasite has the singular ability to phagocytize a variety of different live or death cells. Phagocytosis of red blood cells by E. histolytica trophozoites is a complex phenomenon related with amebic pathogenicity and nutrition.

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Attachment of oral bacteria to titanium surfaces: An SEM study

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100170074 ◽

1994 ◽

Vol 52 ◽

pp. 468-469

Author(s):

J. E. Laffoon ◽

R. L. Anderson ◽

J. C. Keller ◽

C. D. Wu-Yuan

Keyword(s):

Technical Problem ◽

Titanium Implant ◽

Oral Bacteria ◽

Bacterial Cells ◽

Thin Sections ◽

Surface Ultrastructure ◽

Sem Study ◽

Key Factor ◽

Titanium Surfaces

Titanium (Ti) dental implants have been used widely for many years. Long term implant failures are related, in part, to the development of peri-implantitis frequently associated with bacteria. Bacterial adherence and colonization have been considered a key factor in the pathogenesis of many biomaterial based infections. Without the initial attachment of oral bacteria to Ti-implant surfaces, subsequent polymicrobial accumulation and colonization leading to peri-implant disease cannot occur. The overall goal of this study is to examine the implant-oral bacterial interfaces and gain a greater understanding of their attachment characteristics and mechanisms. Since the detailed cell surface ultrastructure involved in attachment is only discernible at the electron microscopy level, the study is complicated by the technical problem of obtaining titanium implant and attached bacterial cells in the same ultra-thin sections. In this study, a technique was developed to facilitate the study of Ti implant-bacteria interface.Discs of polymerized Spurr’s resin (12 mm x 5 mm) were formed to a thickness of approximately 3 mm using an EM block holder (Fig. 1). Titanium was then deposited by vacuum deposition to a film thickness of 300Å (Fig. 2).

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Forum: Morphological Awareness as a Key Factor in Language-Literacy Success for Academic Achievement

Language Speech and Hearing Services in Schools ◽

10.1044/2020_lshss-20-00064 ◽

2020 ◽

Vol 51 (3) ◽

pp. 509-513

Author(s):

Ashley Bourque Meaux ◽

Julie A. Wolter ◽

Ginger G. Collins

Keyword(s):

Academic Achievement ◽

Academic Success ◽

Literacy Development ◽

Morphological Awareness ◽

Language And Literacy ◽

Speech Language Pathologists ◽

School Based ◽

Literacy Success ◽

Key Factor ◽

Language And Literacy Development

Purpose This article introduces the Language, Speech, and Hearing Services in Schools Forum: Morphological Awareness as a Key Factor in Language-Literacy Success for Academic Achievement. The goal of this forum is to relate the influence morphological awareness (MA) has on overall language and literacy development with morphology acting as the “binding agent” between orthography, phonology, and semantics ( Perfetti, 2007 ) in assessment and intervention for school-aged children. Method This introduction provides a foundation for MA development and explores the influence MA has over the course of school-aged language and literacy development. Through summaries of the 11 articles in this forum, school-based speech-language pathologists will be able to convey the importance of MA to promote successful educational outcomes for kindergarten to adolescent students. The forum explores researcher-developed assessments used to help identify MA skill level in first- through eighth-grade students at risk for literacy failure to support instructional needs. The forum also provides school-based speech-language pathologists with details to design and implement MA interventions to support academic success for school-aged students with varying speech-language needs (e.g., dual language emersion, vocabulary development, reading comprehension) using various service delivery models (e.g., small group, classroom-based, intensive summer camps). Conclusion MA is effective in facilitating language and literacy development and as such can be an ideally focused on using multilinguistic approaches for assessment and intervention. The articles in this issue highlight the importance in assessment measures and intervention approaches that focus on students' MA to improve overall academic success in children of all ages and abilities.

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