scholarly journals Crack channelling mechanisms in brittle coating systems under moisture or temperature gradients

2020 ◽  
Vol 225 (1) ◽  
pp. 1-30
Author(s):  
E. Bosco ◽  
A. S. J. Suiker ◽  
N. A. Fleck
Keyword(s):  
Elastic Modulus ◽  
Failure Mechanism ◽  
Paint Layer ◽  
Substrate Thickness ◽  
Indoor Climate ◽  
Brittle Coating ◽  
Climate Fluctuations ◽  
Art Objects ◽  
Wide Range ◽  
Moisture State

AbstractCrack channelling is predicted in a brittle coating-substrate system that is subjected to a moisture or temperature gradient in the thickness direction. Competing failure scenarios are identified, and are distinguished by the degree to which the coating-substrate interface delaminates, and whether this delamination is finite or unlimited in nature. Failure mechanism maps are constructed, and illustrate the sensitivity of the active crack channelling mechanism and associated channelling stress to the ratio of coating toughness to interfacial toughness, to the mismatch in elastic modulus and to the mismatch in coefficient of hygral or thermal expansion. The effect of the ratio of coating to substrate thickness upon the failure mechanism and channelling stress is also explored. Closed-form expressions for the steady-state delamination stress are derived, and are used to determine the transition value of moisture state that leads to unlimited delamination. Although the results are applicable to coating-substrate systems in a wide range of applications, the study focusses on the prediction of cracking in historical paintings due to indoor climate fluctuations, with the objective of helping museums developing strategies for the preservation of art objects. For this specific application, crack channelling with delamination needs to be avoided under all circumstances, as it may induce flaking of paint material. In historical paintings, the substrate thickness is typically more than ten times larger than the thickness of the paint layer; for such a system, the failure maps constructed from the numerical simulations indicate that paint delamination is absent if the delamination toughness is larger than approximately half of the mode I toughness of the paint layer. Further, the transition between crack channelling with and without delamination appears to be relatively insensitive to the mismatch in the elastic modulus of the substrate and paint layer. The failure maps developed in this work may provide a useful tool for museum conservators to identify the allowable indoor humidity and temperature fluctuations for which crack channelling with delamination is prevented in historical paintings.

EFFECTS OF SUBSTRATE DEFORMABILITY ON CELL BEHAVIORS: ELASTIC MODULUS VERSUS THICKNESS

2017 ◽  
Vol 17 (05) ◽  
pp. 1750088 ◽  
Author(s):  
ZAHRA GOLI-MALEKABADI ◽  
MOHAMMAD TAFAZZOLI-SHADPOUR ◽  
EHSAN SEYEDJAFARI
Keyword(s):  
Cell Proliferation ◽  
Elastic Modulus ◽  
Umbilical Vein ◽  
Cell Behavior ◽  
Substrate Thickness ◽  
Microfluidic Chips ◽  
Cell Behaviors ◽  
Varying Thickness ◽  
Wide Range ◽  
Umbilical Vein Endothelial Cells

The deformability of the substrate stimulating cell mechanotransduction depends not only on elastic modulus but also on the thickness. Polydimethylsiloxane (PDMS) which is widely used in microfluidic chips and platforms can be fabricated in a wide range of elastic modulus and thickness. In this study, we cultured human umbilical vein endothelial cells (HUVECs) on four groups of PDMS substrates of varying thickness and elastic modulus to examine effects of these parameters on morphology, viability and proliferation of cells. Both elastic modulus and thickness affected cell behavior. In general, the thickness of substrates had relatively higher impact on endothelial morphology than elastic modulus. Elongation of HUVECs on thick substrates was more intense compared to those on thin substrates. Both lowering thickness and reducing elastic modulus of PDMS decreased the viability of HUVECs, although thickness was more influential. Decrease in substrate thickness reduced cell proliferation regardless of substrate elastic modulus. In conclusion, our results suggest that endothelial behavior depends on substrate deformability, but cells react differently to the elastic modulus and thickness of PDMS by morphology, viability and growth. Results can improve the comprehension of cell mechanotransduction.

scholarly journals Microstructure, Hardness, and Elastic Modulus of a Multibeam-Sputtered Nanocrystalline Co-Cr-Fe-Ni Compositional Complex Alloy Film

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3357
Author(s):  
Péter Nagy ◽  
Nadia Rohbeck ◽  
Zoltán Hegedűs ◽  
Johann Michler ◽  
László Pethö ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Crystallite Size ◽  
Physical Vapor Deposition ◽  
Defect Density ◽  
Lattice Defect ◽  
Chemical Compositions ◽  
Line Profile Analysis ◽  
Face Centered Cubic ◽  
Complex Alloy ◽  
Wide Range

A nanocrystalline Co-Cr-Ni-Fe compositional complex alloy (CCA) film with a thickness of about 1 micron was produced by a multiple-beam-sputtering physical vapor deposition (PVD) technique. The main advantage of this novel method is that it does not require alloy targets, but rather uses commercially pure metal sources. Another benefit of the application of this technique is that it produces compositional gradient samples on a disk surface with a wide range of elemental concentrations, enabling combinatorial analysis of CCA films. In this study, the variation of the phase composition, the microstructure (crystallite size and defect density), and the mechanical performance (hardness and elastic modulus) as a function of the chemical composition was studied in a combinatorial Co-Cr-Ni-Fe thin film sample that was produced on a surface of a disk with a diameter of about 10 cm. The spatial variation of the crystallite size and the density of lattice defects (e.g., dislocations and twin faults) were investigated by X-ray diffraction line profile analysis performed on the patterns taken by synchrotron radiation. The hardness and the elastic modulus were measured by the nanoindentation technique. It was found that a single-phase face-centered cubic (fcc) structure was formed for a wide range of chemical compositions. The microstructure was nanocrystalline with a crystallite size of 10–27 nm and contained a high lattice defect density. The hardness and the elastic modulus values measured for very different compositions were in the ranges of 8.4–11.8 and 182–239 GPa, respectively.

scholarly journals Influence of Alumina Nanofibers Sintered by the Spark Plasma Method on Nickel Mechanical Properties

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 548 ◽  
Author(s):  
Leonid Agureev ◽  
Valeriy Kostikov ◽  
Zhanna Eremeeva ◽  
Svetlana Savushkina ◽  
Boris Ivanov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Strength Properties ◽  
Alumina Nanoparticles ◽  
Metal Powders ◽  
Wide Range ◽  
The Matrix ◽  
Spark Plasma ◽  
Average Size

The article presents the study of alumina nanoparticles’ (nanofibers) concentration effect on the strength properties of pure nickel. The samples were obtained by spark plasma sintering of previously mechanically activated metal powders. The dependence of the grain size and the relative density of compacts on the number of nanofibers was investigated. It was found that with an increase in the concentration of nanofibers, the average size of the matrix particles decreased. The effects of the nanoparticle concentration (0.01–0.1 wt.%) on the elastic modulus and tensile strength were determined for materials at 25 °C, 400 °C, and 750 °C. It was shown that with an increase in the concentration of nanofibers, a 10–40% increase in the elastic modulus and ultimate tensile strength occurred. A comparison of the mechanical properties of nickel in a wide range of temperatures, obtained in this work with materials made by various technologies, is carried out. A description of nanofibers’ mechanisms of influence on the structure and mechanical properties of nickel is given. The possible impact of impurity phases on the properties of nickel is estimated. The tendency of changes in the mechanical properties of nickel, depending on the concentration of nanofibers, is shown.

Consistent red luminescence in π-conjugated polymers with tuneable elastic moduli over five orders of magnitude

2020 ◽  
Vol 7 (5) ◽  
pp. 1421-1426 ◽  
Author(s):  
Zhenfeng Guo ◽  
Akira Shinohara ◽  
Chengjun Pan ◽  
Florian J. Stadler ◽  
Zhonghua Liu ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Conjugated Polymers ◽  
Elastic Moduli ◽  
Luminescent Properties ◽  
Side Chains ◽  
Wide Range ◽  
Alkyl Side Chains ◽  
Red Luminescence

Bulky but flexible alkyl side chains enable π-conjugated polymers to possess wide-range elastic modulus tuneability, yet consistent red luminescent properties.

scholarly journals Experimental Research on the Mechanical Characteristics and the Failure Mechanism of Coal-Rock Composite under Uniaxial Load

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Ke Yang ◽  
Zhen Wei ◽  
Xiaolou Chi ◽  
Yonggang Zhang ◽  
Litong Dou ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Crack Propagation ◽  
Failure Mechanism ◽  
Poisson’S Ratio ◽  
Mechanical Characteristics ◽  
Poisson's Ratio ◽  
Energy Value ◽  
Coal Rock

Due to the influence of the component structure and combination modes, the mechanical characteristics and failure modes of the coal-rock composite show different characteristics from the monomer. In order to explore the effect of different coal-rock ratios on the deformation and the failure law of the combined sample, the RMT rock mechanics test system and acoustic emission real-time monitoring system are adopted to carry out uniaxial compression tests on coal, sandstone, and three kinds of combined samples. The evolution rules of the mechanical parameters of the combined samples, such as the uniaxial compressive strength, elastic modulus, and Poisson’s ratio, are obtained. The expansion and failure deformation characteristics of the combined sample are analyzed. Furthermore, the evolution laws of the fractal and acoustic emission signals are combined to reveal the crack propagation and failure mechanism of the combined samples. The results show that the compressive strength and elastic modulus of the combined sample increase with the decrease of the coal-rock ratios, and Poisson’s ratio decreases with the decrease of the coal-rock ratios. The strain softening weakens at the postpeak stage, which shows an apparent brittle failure. The combined sample of coal and sandstone has different degrees of damages under load. The coal is first damaged with a high degree of breakage, with obvious tensile failure. The acoustic emission energy value presents different stage characteristics with increasing load. Crackling sound occurs in the destroy section before the sample reaches the peak, along with small coal block ejection and the partial destruction. The energy value fluctuates violently, with the appearance of several peaks. At the postpeak stage, the coal samples expand rapidly with a loud crackling sound in the destroy section, and the energy value increases dramatically. The crack propagation induces the damage in the sandstone; when the energy reaches the limit value, the instantaneous release of elastic energy leads to the overall structural instability.

scholarly journals Structure and Biodiversity of Rhodolith Seabeds: A Special Issue

Diversity ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 300 ◽  
Author(s):  
Fernando Tuya
Keyword(s):  
South Africa ◽  
Large Scale ◽  
Algal Species ◽  
Taxonomic Composition ◽  
High Latitudes ◽  
Decapod Crustaceans ◽  
Special Issue ◽  
Associated Fauna ◽  
Climate Fluctuations ◽  
Wide Range

Rhodolith seabeds function as ‘ecosystems engineers’, which globally provide a range of ‘ecosystem services’. However, knowledge on the structure, composition and distribution of rhodolith seabeds is still lacking. This Special Issue comprises six articles, addressing specific questions of rhodolith seabeds, and covering a wide range of topics. Two papers provide new large-scale information on the presence, structure and distribution of rhodolith beds at two southern hemisphere areas, in particular continental shelfs off South Africa and Brazil. Another two studies contributed to the discovery on new algal species from rhodolith beds, including Sporolithon franciscanum, a new rhodolith-forming species from Brazil, and the small benthic alga Schizocladia ischiensis. In terms of associated fauna, the taxonomic composition and patterns of abundance of decapod crustaceans are described in another article, including the description of a depth-partitioning in the abundance of juveniles and adults of the crab Nanocassiope melanodactylus. Rhodoliths are often present in fossilized deposits, so we can track changes in their presence with climate fluctuations. High temperatures during the Eocene and widespread oligotrophic conditions are finally connected with low abundances of rhodolith beds at mid and high latitudes, despite a larger presence at equatorial regions.

Comparative Study on the Elastic Modulus of Polymer Concrete

2015 ◽  
Vol 1129 ◽  
pp. 145-150
Author(s):  
Kyu Seok Yeon ◽  
Kwan Kyu Kim ◽  
Chul Young Kim ◽  
Jae Heum Yeon
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Goodness Of Fit ◽  
Unsaturated Polyester ◽  
Acrylic Resin ◽  
Prediction Equation ◽  
Polymer Concrete ◽  
Wide Range ◽  
Structural Applications ◽  
Using Data

Polymer concrete is used for a wide range of precast structural applications and repair works for existing infrastructures. For these applications, one of the key mechanical propertiesthatneed to be consideredis the elastic modulus. In this study, the relationship between elastic modulus and compressive strength of polymer concrete made with three different types of resin (i.e., unsaturated polyester resin, acrylic resin, and epoxy resin) is comprehensively investigated using data sets available from previous studies in order to develop a prediction equation for elastic modulus that can be generally applied to polymer concrete. Results showed that the equation developed under this study can be reasonably adopted for the predictions of polymer concrete's elastic modulus as a function of compressive strength because the prediction equation has a high goodness of fit asrepresented by a R2 value of 0.77

Deep cavity flow mechanism of pipe penetration in clay

2012 ◽  
Vol 49 (1) ◽  
pp. 59-69 ◽  
Author(s):  
Kee Kiat Tho ◽  
Chun Fai Leung ◽  
Yean Khow Chow ◽  
Andrew Clennel Palmer
Keyword(s):  
Failure Mechanism ◽  
Practical Importance ◽  
Data Interpretation ◽  
Cavity Flow ◽  
Flow Mechanism ◽  
Deep Cavity ◽  
Wide Range ◽  
Smooth Pipe ◽  
Bearing Capacity Factor ◽  
Combination Of Material

The evolution of penetration resistance as a function of penetration depth of a pipe into a cohesive seabed is of practical importance, particularly in the areas of pipeline on-bottom stability assessment and T-bar penetrometer data interpretation. In the past, this subject was addressed primarily in a discontinuous manner by separating the penetration response into two broad regimes of shallow and deep penetrations followed by deriving plasticity solutions assuming a simplified “wished-in-place” configuration. In this manner, the effects of evolving seabed topology and the progressive transition from a shallow failure mechanism to a deep failure mechanism are neglected. This paper aims to provide greater insights into the transition zone, which is especially important for the interpretation of T-bar test data at shallow depths. In this study, the penetration response of a smooth pipe over a wide range of normalized clay strengths is numerically simulated. A deep cavity flow mechanism where the bearing capacity factor is 12% less than the conventional full-flow mechanism is identified and found to be operative up to a depth of 10 pipe diameters under a certain combination of material properties. An analysis method is proposed to predict the load–penetration response for a given set of clay strengths and pipe diameters.

Examination Report: The Polychromy of the Arch of Titus Menorah Relief

Images ◽  
2012 ◽  
Vol 6 (1) ◽  
pp. 26-29 ◽  
Author(s):  
Heinrich Piening
Keyword(s):  
White Light ◽  
Paint Layer ◽  
Spectrometry Analysis ◽  
Art Objects ◽  
Reflected Light ◽  
Technical Report ◽  
Digital Restoration ◽  
Yellow Ochre ◽  
Non Destructive ◽  
Data Library

Abstract Between June 5 and 7, 2012, the menorah relief of the Arch of Titus in Rome was subjected to UV-VIS spectrometry analysis by the Arch of Titus Digital Restoration Project. This technical report details the methods by which UV-VIS-spectrometry of the menorah relief revealed traces of yellow ochre as a paint layer applied directly to the stone surface of a menorah arm and the front of the menorah base. UV-VIS spectrometry is a non-destructive technique used to identify colorants. The surface to be examined is briefly illuminated by white light. From the reflected light this produces, the portion of white light that has been absorbed by the surface is calculated. The absorbed spectra are then compared with those in a special data library comprising about six thousand spectra of different art objects. Analysis of this data, and the characteristics of the spectra, show that the yellow pigment must have been cleaned and prepared thoroughly before use, and that it was applied as a first coat. Together this suggests that the menorah was originally painted yellow.

scholarly journals CREATING METHODOLOGY OF AN ART OBJECT USING SOFTWARE PACKAGES

2021 ◽  
Vol 3 (2) ◽  
pp. 14-21
Author(s):  
E. Shopina ◽  
M. Markova
Keyword(s):  
Computer Graphics ◽  
Virtual Environment ◽  
3D Modeling ◽  
Computer Programs ◽  
Vector Graphics ◽  
Software Products ◽  
Art Object ◽  
Software Packages ◽  
Art Objects ◽  
Wide Range

Vector graphics and 3D modeling have opened up a wide range of perspectives for designers to create various art objects. The use of computer graphics greatly simplified the process of sketch creating, as it provided the ability to change, add colors, and edit entire groups of objects. 3D modeling made it possible to recreate products, taking into account the smallest details in a virtual environment, compose an interior, and perform animation of various processes. The research object is the computer programs Corel Draw and 3D max and their importance for the methodology of development and creation of art objects. As a result of the study, it was found that vector graphics and 3D modeling programs not only made it easier for designers to create art objects, but also made it possible to improve the level of design by changing the usual perception. According to the authors, software products influenced the development of design, which made it possible to create any objects in a virtual environment.

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