Modelling the change in structure and mechanical properties in dry-snow densification to ice

The regular packing of spheres or polyhedrons of various shapes linked by rigid bonds is presented and discussed as a model of snow structure. Basic structural parameters of this model are: the coordination number and introduced dimensionless factors of friability and rigidity. The snow densification is described as successive changes of these parameters. Use of the model allows us to relate the density increase from ~130 to ~320, ~550, ~700, ~820 and 917 kg m−3, while the coordination number of the structure increases accordingly from 3 (friable hexagonal) to 4 (tetrahedral), 6 (cubic), 8, 10, 12 (dense hexagonal). These structural changes are in good agreement with the critical densities established in experimental studies of snow densification and the physical properties of snow. It is shown that the model presented allows us to estimate the mechanical properties of ice-porous media: Young’s modulus, Poisson’s ratio and strength.

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Changes of Selected Structural and Mechanical Properties of the Strzelin Granites As Induced By Thermal Loads / Wpływ Obciążeń Termicznych Na Zmiany Niektórych Strukturalnych I Mechanicznych Właściwości Granitów Strzelińskich

Archives of Mining Sciences ◽

10.2478/v10267-012-0064-8 ◽

2012 ◽

Vol 57 (4) ◽

pp. 951-974 ◽

Cited By ~ 1

Author(s):

Andrzej Nowakowski ◽

Mariusz Młynarczuk

Keyword(s):

Mechanical Properties ◽

Nuclear Waste ◽

Structural Changes ◽

Structural Parameters ◽

Total Porosity ◽

Fracture Network ◽

Qualitative Description ◽

Temperature Changes ◽

Heating And Cooling ◽

Waste Repositories

Abstract Temperature is one of the basic factors influencing physical and structural properties of rocks. A quantitative and qualitative description of this influence becomes essential in underground construction and, in particular, in the construction of various underground storage facilities, including nuclear waste repositories. The present paper discusses the effects of temperature changes on selected mechanical and structural parameters of the Strzelin granites. Its authors focused on analyzing the changes of granite properties that accompany rapid temperature changes, for temperatures lower than 573ºC, which is the value at which the β - α phase transition in quartz occurs. Some of the criteria for selecting the temperature range were the results of measurements carried out at nuclear waste repositories. It was demonstrated that, as a result of the adopted procedure of heating and cooling of samples, the examined rock starts to reveal measurable structural changes, which, in turn, induces vital changes of its selected mechanical properties. In particular, it was shown that one of the quantities describing the structure of the rock - namely, the fracture network - grew significantly. As a consequence, vital changes could be observed in the following physical quantities characterizing the rock: primary wave velocity (vp), permeability coefficient (k), total porosity (n) and fracture porosity (η), limit of compressive strength (Rσ1) and the accompanying deformation (Rε1), Young’s modulus (E), and Poisson’s ratio (ν).

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Structural and physical properties of 99 complex bulk chalcogenides crystals using first-principles calculations

Scientific Reports ◽

10.1038/s41598-021-89281-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Sahib Hasan ◽

Khagendra Baral ◽

Neng Li ◽

Wai-Yim Ching

Keyword(s):

Mechanical Properties ◽

Physical Properties ◽

First Principles ◽

Experimental Studies ◽

First Principles Calculations ◽

Chalcogenide Semiconductors ◽

Optical And Mechanical Properties ◽

Very Large Database ◽

Unique Composition ◽

Fundamental Physical

AbstractChalcogenide semiconductors and glasses have many applications in the civil and military fields, especially in relation to their electronic, optical and mechanical properties for energy conversion and in enviormental materials. However, they are much less systemically studied and their fundamental physical properties for a large class chalcogenide semiconductors are rather scattered and incomplete. Here, we present a detailed study using well defined first-principles calculations on the electronic structure, interatomic bonding, optical, and mechanical properties for 99 bulk chalcogenides including thirteen of these crytals which have never been calculated. Due to their unique composition and structures, these 99 bulk chalcogenides are divided into two main groups. The first group contains 54 quaternary crystals with the structure composition (A2BCQ4) (A = Ag, Cu; B = Zn, Cd, Hg, Mg, Sr, Ba; C = Si, Ge, Sn; Q = S, Se, Te), while the second group contains scattered ternary and quaternary chalcogenide crystals with a more diverse composition (AxByCzQn) (A = Ag, Cu, Ba, Cs, Li, Tl, K, Lu, Sr; B = Zn, Cd, Hg, Al, Ga, In, P, As, La, Lu, Pb, Cu, Ag; C = Si, Ge, Sn, As, Sb, Bi, Zr, Hf, Ga, In; Q = S, Se, Te; $$\hbox {x} = 1$$ x = 1 , 2, 3; $$\hbox {y} = 0$$ y = 0 , 1, 2, 5; $$\hbox {z} = 0$$ z = 0 , 1, 2 and $$\hbox {n} = 3$$ n = 3 , 4, 5, 6, 9). Moreover, the total bond order density (TBOD) is used as a single quantum mechanical metric to characterize the internal cohesion of these crystals enabling us to correlate them with the calculated properties, especially their mechanical properties. This work provides a very large database for bulk chalcogenides crucial for the future theoretical and experimental studies, opening opportunities for study the properties and potential application of a wide variety of chalcogenides.

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Foam Formation by Compression/Decompression Cycle of Soft Porous Media

Colloids and Interfaces ◽

10.3390/colloids4030031 ◽

2020 ◽

Vol 4 (3) ◽

pp. 31

Author(s):

Phillip Johnson ◽

Mauro Vaccaro ◽

Victor Starov ◽

Anna Trybala

Keyword(s):

Mechanical Properties ◽

Porous Media ◽

Porous Material ◽

Foam Formation ◽

Compression Device ◽

The Media ◽

Minimum Separation ◽

Soft Porous Media ◽

Predicted Values ◽

Good Agreement

A theory of the amount of foam produced by compression/decompression cycles of a soft porous media is developed. The amount of foam produced was found to be dependent on both the amount of surfactant within the media and the minimum separation between the plates of the compression device. The latter is determined by the mechanical properties of the soft media. The theory also shows the importance of the decompression of the media as this is the mechanism of where the air penetrates into the soft porous material. The accumulated air is used during the compression stage for foam formation. The theoretically predicted values of foam mass are found to have good agreement with experimental observations, which validates the theory predictions. The theory also predicts independence of the foam produced in terms of the frequency of compression/decompression cycles, which agrees with our experimental observations.

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Mechanical and Basic Physical Properties of High-Strength Concrete Exposed to Elevated Temperatures

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.760.108 ◽

2018 ◽

Vol 760 ◽

pp. 108-113 ◽

Cited By ~ 1

Author(s):

Lenka Scheinherrová ◽

Monika Čáchová ◽

Michaela Petříková ◽

Lukáš Fiala ◽

Eva Vejmelková ◽

...

Keyword(s):

Mechanical Properties ◽

Physical Properties ◽

Structural Changes ◽

Elevated Temperatures ◽

Water Environment ◽

High Strength ◽

Steel Fibers ◽

Quartz Powder ◽

Matrix Density ◽

Drying Treatment

In this paper, the effect of elevated temperatures on the mechanical and basic properties of two different newly-designed high-strength concretes is studied. The studied materials were prepared from Portland cement, steel fibers, reactive finely milled quartz powder and quartz sand, silica fume, plasticizer, and with a relatively low water/cement ratio of 0.24. The samples were stored in water environment for the first 28 days of hydration to achieve better mechanical properties. Then, after pre-drying at 105 °C to constant mass, the materials were exposed to elevated temperatures of 600 °C and 1000 °C where they were kept for 2 hours. The basic physical properties, such as matrix density, bulk density and open porosity were determined as a function of temperature. Mechanical properties (compressive and flexural strength) were also studied. The measured parameters exhibited a high dependence on temperature and the obtained results pointed to the structural changes of the studied materials. Spalling was not observed because of the pre-drying treatment.

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Thermodynamics of Stable and Metastable Cu-O-H Compounds

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.172-174.973 ◽

2011 ◽

Vol 172-174 ◽

pp. 973-978 ◽

Cited By ~ 7

Author(s):

Pavel A. Korzhavyi ◽

Inna Soroka ◽

Mats Boman ◽

Börje Johansson

Keyword(s):

Experimental Data ◽

Perturbation Theory ◽

Physical Properties ◽

Density Functional ◽

Metastable Phase ◽

Experimental Studies ◽

Ambient Conditions ◽

Phonon Spectra ◽

Density Functional Perturbation Theory ◽

Good Agreement

We apply density functional perturbation theory together with experimental studies in order to investigate the structure and physical properties of possible stable and metastable copper(I) compounds with oxygen and hydrogen. Copper(I) hydride, CuH, is found to be a metastable phase which decomposes at ambient conditions and exhibiting a semiconducting gap in the electronic spectrum. The calculated structure and phonon spectra are found to be in good agreement with experimental data. The phonon spectra of a novel metastable phase, copper(I) hydroxide, are also determined.

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Approaches for process and structural finite element simulations of braided ligament replacements

Journal of Industrial Textiles ◽

10.1177/1528083716648765 ◽

2016 ◽

Vol 47 (3) ◽

pp. 408-425 ◽

Cited By ~ 2

Author(s):

Thomas Gereke ◽

Oliver Döbrich ◽

Dilbar Aibibu ◽

Jorg Nowotny ◽

Chokri Cherif

Keyword(s):

Mechanical Properties ◽

Finite Element ◽

Process Model ◽

Structural Model ◽

Structural Parameters ◽

Healing Process ◽

Resorbable Polymers ◽

Wide Range ◽

Experimental Trials ◽

Good Agreement

To prevent the renewed rupture of ligaments and tendons prior to the completed healing process, which frequently occurs in treated ruptured tendons, a temporary support structure is envisaged. The limitations of current grafts have motivated the investigation of tissue-engineered ligament replacements based on the braiding technology. This technology offers a wide range of flexibility and adjustable geometrical and structural parameters. The presented work demonstrates the possible range for tailoring the mechanical properties of polyester braids and a variation of the braiding process parameters. A finite element simulation model of the braiding process was developed, which allows the optimization of production parameters without the performance of further experimental trials. In a second modelling and simulation step, mechanical properties of the braided structures were virtually determined and compared with actual tests. The digital element approach was used for the yarns in the numerical model. The results show very good agreement for the process model in terms of braiding angles and good agreement for the structural model in terms of force-strain behaviour. With a few adaptions, the models can, thus, be applied to actual ligament replacements made of resorbable polymers.

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The Role of Structure on Mechanical Properties of Nonwoven Fabrics

International Nonwovens Journal ◽

10.1177/1558925001os-01000209 ◽

2001 ◽

Vol os-10 (2) ◽

pp. 1558925001OS-01 ◽

Cited By ~ 2

Author(s):

H.S. Kim ◽

B. Pourdeyhimi

Keyword(s):

Mechanical Properties ◽

Structural Changes ◽

Maximum Stress ◽

Structural Parameters ◽

Bonding Temperature ◽

Tensile Modulus ◽

Orientation Distribution ◽

Nonwoven Fabrics ◽

Fiber Orientation Distribution

The mechanical properties, namely, tensile modulus, maximum stress in tension and elongation at maximum stress of thermally point-bonded nonwoven fabrics with different bonding temperature have been evaluated. Image acquisition and analysis techniques have been used to quantify structural parameters such as fiber orientation distribution function, bond-region strain, and unit cell strain during controlled-deformation experiments and to identify failure mechanisms. We have shown that an in situ experimental visualization and measurement of the structural changes occurring during controlled-deformation experiments can help establish links between mechanical properties and the structure properties of nonwoven fabrics.

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Physical Properties and Durability of Lime-Cement Mortars Prepared with Water Containing Micro-Nano Bubbles of Various Gases

Materials ◽

10.3390/ma14081902 ◽

2021 ◽

Vol 14 (8) ◽

pp. 1902

Author(s):

Małgorzata Grzegorczyk-Frańczak ◽

Danuta Barnat-Hunek ◽

Wojciech Andrzejuk ◽

Jacek Zaburko ◽

Monika Zalewska ◽

...

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Physical Properties ◽

Tap Water ◽

Experimental Studies ◽

Total Porosity ◽

Capillary Absorption ◽

Cement Mortars ◽

Influence Of Water ◽

Mixing Water

The paper presents the experimental studies on the effect of the water containing micro-nano bubbles of various gases on the physico-mechanical properties of lime-cement mortars. In total, 7 types of mortars were prepared: with water containing the micro-nano bubbles of O2, O3 or CO2 as 50% or 100% substitute of ordinary mixing water (tap water) and the reference mortar prepared using tap water. In order to determine the influence of water with micro-nano bubbles of gases, the consistency of fresh mortar and the physical properties of hardened mortar, i.e., specific and apparent density, total porosity, water absorption by weight and capillary absorption, were established. The mechanical strength of the considered mortars was studied as well by conducting the tests for flexural and compressive strengths following 14, 28 and 56 days. Reduced workability and capillary absorption were observed in the modified mortars within the range of 0.9–8.5%. The mortars indicated an increase in the flexural strength after 28 days ranging from 3.4% to 23.5% and improved compressive strength in 1.2–31%, in comparison to the reference mortar. The conducted studies indicated increased flexural and compressive strengths along with the share of micro-nano bubbles of gases in the mixing water.

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Effect of Center Crack on Mechanical Properties of Graphene

Journal of Nano Research ◽

10.4028/www.scientific.net/jnanor.55.22 ◽

2018 ◽

Vol 55 ◽

pp. 22-31

Author(s):

Mohsen Motamedi ◽

Amin Esfandiarpour

Keyword(s):

Mechanical Properties ◽

Tensile Strain ◽

Thin Sheet ◽

Experimental Studies ◽

Dynamics Simulation ◽

Graphene Sheets ◽

Strain Rates ◽

Center Crack ◽

Good Agreement ◽

Defected Graphene

Graphene is a thin sheet with special properties and complicated mechanical behavior. It’s important to study graphene experimentally and theoretically. Stone–Wales defects, cracks and atom vacancy are popular defects in carbon allotropes especially in graphene. In this paper, effect of center cracks on graphene was discussed. At first, mechanical properties of non-defected graphene sheet was obtained using molecular dynamics simulation. Comparing result with theoretical and experimental studies showing good agreements and proofing the results. Then, 8 different cracks were considered in center of graphene sheets. Stress-strain curves of defected graphene sheets with different tension strain rates were plotted. The results showed that increasing crack length lead to decreasing Young’s modulus of graphene from 870GPa to 670GPa. Also, fracture occurred in less tensile strain. In the following, structural molecular mechanics method was used to simulate cracked graphene sheets. The results showed good agreement between two methods.

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