The Relationship between the Visco-Elastic and Structural Properties of Fine-Grained Snow

New and felt-like snow was sieved and sintered at a constant temperature in order to produce homogeneous samples of fine, rounded-grain snow with a density in the range 270–340 kg m−3. The structure of single samples was changed in stages by non-destructive uniaxial compression. This deformation, which amounted to 30%, took place within 8 hours (thus limiting temperature metamorphism). At each stage the Young’s modulus was measured quasi-statically and the creep behaviour under constant uniaxial compression was recorded. Stereological analysis of sections from the samples provided mean values for both grain-bond and grain properties. The Young’s modulus increased with density slightly more strongly than linearly, whereas the low-stress viscosity in unconfined compression increased nearly exponentially for densities less than 380 kg m−3. The maximum densification resulted in a 15-fold increase in the measured visco-elastic properties. However, the number of grain bonds per unit mass increased linearly by a factor in the range 1.5 to 2 while the average grain-bond size remained constant. It is concluded that only a fraction of the grain bonds in a snow sample transmit an applied stress, and that the new grain bonds formed during the deformation of a snow sample determine the visco-elastic properties of snow. The hypothesis that chains, defined as series of stress-bearing grains, are the basic units of snow structure is developed. Semi-quantitative calculations developed from the chain concept explain the observed variations in the visco-elastic properties.

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A Quasi-Static Quantitative Ultrasound Elastography Algorithm Using Optical Flow

Sensors ◽

10.3390/s21093010 ◽

2021 ◽

Vol 21 (9) ◽

pp. 3010

Author(s):

Raphael Lamprecht ◽

Florian Scheible ◽

Marion Semmler ◽

Alexander Sutor

Keyword(s):

Optical Flow ◽

Young’S Modulus ◽

Elastic Properties ◽

Young's Modulus ◽

Image Data ◽

Maximum Error ◽

Ultrasound Elastography ◽

Static Compression ◽

Tissue Properties ◽

A Performance

Ultrasound elastography is a constantly developing imaging technique which is capable of displaying the elastic properties of tissue. The measured characteristics could help to refine physiological tissue models, but also indicate pathological changes. Therefore, elastography data give valuable insights into tissue properties. This paper presents an algorithm that measures the spatially resolved Young’s modulus of inhomogeneous gelatin phantoms using a CINE sequence of a quasi-static compression and a load cell measuring the compressing force. An optical flow algorithm evaluates the resulting images, the stresses and strains are computed, and, conclusively, the Young’s modulus and the Poisson’s ratio are calculated. The whole algorithm and its results are evaluated by a performance descriptor, which determines the subsequent calculation and gives the user a trustability index of the modulus estimation. The algorithm shows a good match between the mechanically measured modulus and the elastography result—more precisely, the relative error of the Young’s modulus estimation with a maximum error 35%. Therefore, this study presents a new algorithm that is capable of measuring the elastic properties of gelatin specimens in a quantitative way using only the image data. Further, the computation is monitored and evaluated by a performance descriptor, which measures the trustability of the results.

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A parametric prediction of the Young’s modulus of polymers enhanced with ΜWCNTs

MATEC Web of Conferences ◽

10.1051/matecconf/201823300025 ◽

2018 ◽

Vol 233 ◽

pp. 00025

Author(s):

P.V. Polydoropoulou ◽

K.I. Tserpes ◽

Sp.G. Pantelakis ◽

Ch.V. Katsiropoulos

Keyword(s):

Young’S Modulus ◽

Elastic Properties ◽

Young's Modulus ◽

Experimental Results ◽

Scale Model ◽

Fe Model ◽

Multi Scale ◽

Unit Cells ◽

Random Dispersion

In this work a multi-scale model simulating the effect of the dispersion, the waviness as well as the agglomerations of MWCNTs on the Young’s modulus of a polymer enhanced with 0.4% MWCNTs (v/v) has been developed. Representative Unit Cells (RUCs) have been employed for the determination of the homogenized elastic properties of the MWCNT/polymer. The elastic properties computed by the RUCs were assigned to the Finite Element (FE) model of a tension specimen which was used to predict the Young’s modulus of the enhanced material. Furthermore, a comparison with experimental results obtained by tensile testing according to ASTM 638 has been made. The results show a remarkable decrease of the Young’s modulus for the polymer enhanced with aligned MWCNTs due to the increase of the CNT agglomerations. On the other hand, slight differences on the Young’s modulus have been observed for the material enhanced with randomly-oriented MWCNTs by the increase of the MWCNTs agglomerations, which might be attributed to the low concentration of the MWCNTs into the polymer. Moreover, the increase of the MWCNTs waviness led to a significant decrease of the Young’s modulus of the polymer enhanced with aligned MWCNTs. The experimental results in terms of the Young’s modulus are predicted well by assuming a random dispersion of MWCNTs into the polymer.

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Phase Formation, Microstructure and Mechanical Properties of Mg67Ag33 as Potential Biomaterial

Metals ◽

10.3390/met11030461 ◽

2021 ◽

Vol 11 (3) ◽

pp. 461

Author(s):

Konrad Kosiba ◽

Konda Gokuldoss Prashanth ◽

Sergio Scudino

Keyword(s):

Mechanical Properties ◽

Young’S Modulus ◽

Young's Modulus ◽

Equilibrium Phase ◽

Antibacterial Properties ◽

Equilibrium Phase Diagram ◽

Compressive Yield Strength ◽

X Ray ◽

Fine Grained ◽

Equilibrium Phases

The phase and microstructure formation as well as mechanical properties of the rapidly solidified Mg67Ag33 (at. %) alloy were investigated. Owing to kinetic constraints effective during rapid cooling, the formation of equilibrium phases is suppressed. Instead, the microstructure is mainly composed of oversaturated hexagonal closest packed Mg-based dendrites surrounded by a mixture of phases, as probed by X-ray diffraction, electron microscopy and energy dispersive X-ray spectroscopy. A possible non-equilibrium phase diagram is suggested. Mainly because of the fine-grained dendritic and interdendritic microstructure, the material shows appreciable mechanical properties, such as a compressive yield strength and Young’s modulus of 245 ± 5 MPa and 63 ± 2 GPa, respectively. Due to this low Young’s modulus, the Mg67Ag33 alloy has potential for usage as biomaterial and challenges ahead, such as biomechanical compatibility, biodegradability and antibacterial properties are outlined.

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High-Temperature Elastic Properties of Yttrium-Doped Barium Zirconate

Metals ◽

10.3390/met11060968 ◽

2021 ◽

Vol 11 (6) ◽

pp. 968

Author(s):

Fumitada Iguchi ◽

Keisuke Hinata

Keyword(s):

High Temperature ◽

Young’S Modulus ◽

Elastic Properties ◽

Measurement Method ◽

Young's Modulus ◽

Barium Zirconate ◽

Shear Moduli ◽

Ceramic Fuel ◽

Yttrium Concentration ◽

Ceramic Fuel Cells

The elastic properties of 0, 10, 15, and 20 mol% yttrium-doped barium zirconate (BZY0, BZY10, BZY15, and BZY20) at the operating temperatures of protonic ceramic fuel cells were evaluated. The proposed measurement method for low sinterability materials could accurately determine the sonic velocities of small-pellet-type samples, and the elastic properties were determined based on these velocities. The Young’s modulus of BZY10, BZY15, and BZY20 was 224, 218, and 209 GPa at 20 °C, respectively, and the values decreased as the yttrium concentration increased. At high temperatures (>20 °C), as the temperature increased, the Young’s and shear moduli decreased, whereas the bulk modulus and Poisson’s ratio increased. The Young’s and shear moduli varied nonlinearly with the temperature: The values decreased rapidly from 100 to 300 °C and gradually at temperatures beyond 400 °C. The Young’s modulus of BZY10, BZY15, and BZY20 was 137, 159, and 122 GPa at 500 °C, respectively, 30–40% smaller than the values at 20 °C. The influence of the temperature was larger than that of the change in the yttrium concentration.

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Nanoindentation of nanocrystalline ZnO

Journal of Materials Research ◽

10.1557/jmr.1992.0973 ◽

1992 ◽

Vol 7 (4) ◽

pp. 973-979 ◽

Cited By ~ 132

Author(s):

M.J. Mayo ◽

R.W. Siegel ◽

Y.X. Liao ◽

W.D. Nix

Keyword(s):

Strain Rate ◽

Young’S Modulus ◽

Strain Rate Sensitivity ◽

Sintering Temperature ◽

Young's Modulus ◽

Rate Sensitivity ◽

Large Degree ◽

Fine Grained ◽

Nanocrystalline Ceramics ◽

Microstructural Inhomogeneity

A number of nanocrystalline ceramics have been fabricated by the gas phase condensation technique. The mechanical properties of one of the first ceramics produced by this method, nanophase TiO2, have been discussed in an earlier study.1 This paper reports a similar study undertaken to examine the properties of nanocrystalline ZnO. Nanoindenter techniques are used to determine hardness, Young's modulus, and strain rate sensitivity in ultra-fine grained ZnO. Significant properties variations are experienced within a given sample, indicating a large degree of microstructural inhomogeneity. Nevertheless, a distinct evolution in properties can be observed as a function of sintering temperature. Young's modulus and hardness values increase almost linearly with increasing sintering temperature, and, in addition, there also appears to be a linear correlation between the development of the two materials properties. In contrast, strain rate sensitivity is shown to have an inverse dependence on sintering temperature. This dependence appears to be linked to the strong influence of grain size on strain rate sensitivity, so that the lower sintering temperatures, which provide the finer grain sizes, tend to promote strain rate sensitivity. The results of this study are strikingly similar to those obtained earlier for nanophase TiO2, and they indicate that the earlier results could probably be generalized to a much broader range of nanocrystalline ceramics.

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Simulation of Uniaxial Compression for Flexible Fibers of Wheat Straw Using the Discrete Element Method

Transactions of the ASABE ◽

10.13031/trans.13995 ◽

2021 ◽

Vol 64 (6) ◽

pp. 2025-2034

Author(s):

Matthew W Schramm ◽

Mehari Z. Tekeste ◽

Brian L Steward

Keyword(s):

Discrete Element Method ◽

Wheat Straw ◽

Young’S Modulus ◽

Uniaxial Compression ◽

Material Properties ◽

Young's Modulus ◽

Discrete Element ◽

Flexible Fibers ◽

Dem Model ◽

Element Method

HighlightsSimulation of uniaxial compression was performed with flexible fibers modeled in DEM.Bond-specific DEM parameters were found to be sensitive in uniaxial compression.A calibration technique that is not plunger-dependent is shown and validated.Abstract. To accurately simulate a discrete element method (DEM) model, the material properties must be calibrated to reproduce bulk material behavior. In this study, a method was developed to calibrate DEM parameters for bulk fibrous materials using uniaxial compression. Wheat straw was cut to 100.2 mm lengths. A 227 mm diameter cylindrical container was loosely filled with the cut straw. The material was pre-compressed to 1 kPa. A plunger (50, 150, or 225 mm diameter) was then lowered onto the compressed straw at a rate of 15 mm s-1. This experimental procedure was simulated using a DEM model for different material properties to generate a simulated design of experiment (DOE). The simulated plunger had a travel rate of 40 mm s-1. The contact Young’s modulus, bond Young’s modulus, and particle-to-particle friction DEM parameters were found to be statistically significant in the prediction of normal forces on the plunger in the uniaxial compression test. The DEM calibration procedure was used to approximate the mean laboratory results of wheat straw compression with root mean square (RMS) percent errors of 3.77%, 3.02%, and 13.90% for the 50, 150, and 225 mm plungers, respectively. Keywords: Calibration, DEM, DOE, Flexible DEM particle, Uniaxial compression, Wheat straw.

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Elastic properties and breaking strengths of GaS, GaSe and GaTe nanosheets

Nanoscale ◽

10.1039/c8nr01065j ◽

2018 ◽

Vol 10 (27) ◽

pp. 13022-13027 ◽

Cited By ~ 19

Author(s):

Basant Chitara ◽

Assaf Ya'akobovitz

Keyword(s):

Atomic Force Microscopy ◽

Young’S Modulus ◽

Elastic Properties ◽

Young's Modulus ◽

Force Microscopy ◽

Atomic Force ◽

Maximal Strain

The present study highlights the elastic properties of suspended GaS, GaSe and GaTe nanosheets using atomic force microscopy. GaS exhibited the highest Young's modulus (∼173 GPa) among these nanosheets. These materials can withstand maximal stresses of up to 8 GPa and a maximal strain of 7% before breaking, making them suitable for stretchable electronic and optomechanical devices.

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Single-walled carbon nanotubes functionalized by a series of dichlorocarbenes: DFT study

Modern Physics Letters B ◽

10.1142/s0217984916501189 ◽

2016 ◽

Vol 30 (08) ◽

pp. 1650118 ◽

Cited By ~ 1

Author(s):

Igor K. Petrushenko ◽

Konstantin B. Petrushenko

Keyword(s):

Carbon Nanotubes ◽

Young’S Modulus ◽

Elastic Properties ◽

Density Functional ◽

Young's Modulus ◽

Strong Dependence ◽

Single Walled Carbon Nanotubes ◽

Binding Energies ◽

Single Walled Carbon ◽

Walled Carbon Nanotubes

The structural and elastic properties of neutral and ionized dichlorocarbene (CCl2) functionalized single-walled carbon nanotubes (SWCNTs) were studied using density functional theory (DFT). The Young’s modulus of ionized pristine SWCNTs is found to decrease in comparison to that of neutral models. The interesting effect of increase in Young’s modulus values of ionized functionalized SWCNTs is observed. We ascribe this feature to the concurrent processes of the bond elongation on ionization and the local deformation on cycloaddition. The strong dependence of the elasticity modulus on the number of addends is also observed. However, the CCl2-attached SWCNTs in their neutral and ionized forms remain strong enough to be suitable for the reinforcement of composites. In contrast to the elastic properties, the binding energies do not change significantly, irrespective of CCl2 coverage.

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