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作者： Yakun Fan Mingxin Zheng Junhua Wu School of Civil Engineering and Architecture Nanchang Hangkong University School of Civil Engineering and Architecture East China Jiaotong University

The macroscopic mechanical properties of soil are essentially determined by its microstructure, which is a comprehensive manifestation of the external microstructure of soil. This paper conducts microscopic tests on coal-bearing soil with different moisture content under dry-wet circulation conditions, and uses Image-Pro Plus software to preprocess and image the SEM images of coal-bearing soil samples to characterize the size and orientation of coal-bearing soil particles and pores. The microstructure parameters of average diameter and orientation frequency of shape and orientation are quantitatively analyzed, revealing the change rule of the microstructure parameters of unsaturated coal-bearing soil under dry-wet circulation.

关键词： Coal-bearing soil microstructure parameters dry-wet circulation microscopic tests

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Magneto-electro-elastic properties of multiferroic composites containing periodic distribution of general multi-coated inhomogeneities

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INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE 2016年 103卷 59-76页

作者： Hashemi, Roohollah Rutgers State Univ Dept Mech & Aerosp Engn New Brunswick NJ 08903 USA

In this paper, a homogenization scheme with several desirable features is developed to determine the overall magneto-electro-elastic behavior of multiferroic composite materials containing periodic distribution of multi-inhomogeneities. The configuration of a typical inhomogeneity system is taken to be composed of an inner ellipsoidal particle surrounded by many coating layers of ellipsoidal shape. As such, the morphology of composite is sufficiently general, and then the developed methodology can be quite robust to handle a wide range of problems. Through the present analysis, we first adopt the equivalent inclusion principle in conjunction with a superposition procedure to decompose the multi-inhomogeneity system into a series of single-inclusion problems with position dependent eigenstrain electric magnetic fields. The periodic microstructure will be accounted for through the Fourier series expansion of field quantities. The local form of consistency equations are then called upon, and integrated to give the expression for the average eigenfields. Finally, considering the relation between far-field loads and the local microscopic fields in the constituent phases the overall effective moduli of composite are obtained in terms of derived average eigenfields. The accuracy and generality of proposed theory is verified through consideration of several three-phase multiferroic composites with complex microstructures. In this process, the strong dependence of overall behavior of fibrous and particulate multiferroics on the microstructure parameters, such as the interface condition, thickness, eccentricity and material properties of core inhomogeneities and their coating layers is well demonstrated. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Multiferroic composite Multi-inhomogeneity Magneto-electric coefficient Homogenization scheme microstructure parameters Interface condition

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Dispersion properties of the phononic crystal consisting of ellipse-shaped particles

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JOURNAL OF SOUND AND VIBRATION 2016年第0期384卷 163-176页

作者： Pavlov, I. S. Vasiliev, A. A. Porubov, A. V. Russian Acad Sci Mech Engn Res Inst 85 Belinsky Str Nizhnii Novgorod 603024 Russia Nizhny Novgorod Lobachevsky State Univ 23 Gagarin Av Nizhnii Novgorod 603950 Russia Tver State Univ Dept Math Modelling Sadoviy Per 35 Tver 170002 Russia Inst Problems Mech Engn Bolshoy 61 St Petersburg 199178 Russia St Petersburg State Univ 7-9 Univ Skaya Nab St Petersburg 199034 Russia St Petersburg State Polytech Univ Polytech Skaya St 29 St Petersburg 195251 Russia

A two-dimensional model is considered in the form of a phononic crystal having a rectangular lattice with elastically interacting ellipse-shaped particles possessing two translational and one rotational degrees of freedom. The linear differential-difference equations are obtained by the method of structural modeling to describe propagation of longitudinal, transverse and rotational waves in the medium. It is found analytically how the coefficients of the equations depend on the sizes of the particle and on the parameters of interactions between them. The dispersion properties of the model are analyzed. Existence of a backward wave is established. The threshold frequencies of acoustic and rotational waves in some crystalline materials with cubic symmetry are estimated. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Phononic crystal Structural modeling Rectangular lattice Ellipse-shaped particles microstructure parameters Dispersion properties

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Static Friction of Biomimetic Surface microstructure of PDMS under Wet and Dry Conditions

Static Friction of Biomimetic Surface Microstructure of PDMS...

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Conference on Bioinspiration, Biomimetics, and Bioreplication

作者： Yu, Haiwu Jia, Hongduo Gong, Ling Li, Rong Wang, Caiping Wang, Xiaojie Chinese Acad Sci Hefei Inst Phys Sci Inst Adv Mfg Technol Changzhou 213164 Peoples R China

ISBN: (纸本)9781510600386

Smooth adhesive pad found among arthropods, amphibians, particularly tree frogs, are usually covered with surface microstructure of different shape to enhance the attachment abilities on the smooth substrate. During the last decade, it has gained more attentions in the development of anti-slippery systems by mimicking these unique characteristics. In this paper, we studied a new amphibian species newt by observing their climbing abilities on wet and dry vertical smooth surface, and found that the newts can even hang on the surface with an inclination angle more than 90 degrees without falling. We investigated the toe pad micro-structured surface of the newt by using scanning electron microscopy (SEM), and found that an array of hexagonal cells with micro-ridges on cell borders exists for the larvae;while an array of hexagonal cells separated by microgrooves is for the adult. Inspired by these features, the biomimetic micro-structured surfaces were fabricated using a soft elastomeric material polydimethysiloxane (PDMS). Four different microstructures were chosen to study their tribological properties with a solid substrate under wet and dry conditions. The patterns of the microstructures include round pillar, hexagonal pillar, round pillars surrounded by a closed hexagonal ridge, and round pillars surrounded by a semi-closed hexagonal ridge. The static friction tests were carried out using the multi-functional surface meter TYPE12. The results showed that the area ratio of the micro pillar plays a major role in enhancing the static friction for both wet and dry conditions, while the numerical density of the micro pillar has less effect on the friction enhancement. Among the four kind specimens, the specimen with hexagonal pillars would increase the static friction more than others at the same test conditions when the pillar area ratio is lower than 40%.

关键词： Newt Biomimetic microstructure microstructure parameters Static Friction

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Usable Properties of AlSi7Mg Alloy after Sodium or Strontium Modification

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ARCHIVES OF FOUNDRY ENGINEERING 2016年第3期16卷 129-132页

作者： Tupaj, M. Orlowicz, A. W. Mroz, M. Trytek, A. Markowska, O. Rzeszow Univ Technol Dept Casting & Welding Al Powstancow Warszawy 12 PL-35959 Rzeszow Poland

The paper deals with the effect of microstructure diversified by means of variable cooling rate on service properties of AlSi7Mg cast alloy refined traditionally with Dursalit EG 281, grain refining with titanium-boron and modified with sodium and a variant of the same alloy barbotage-refined with argon and simultaneously grain refining with titanium-boron and modified with strontium. For both alloy variants, the castings were subject to T6 thermal treatment (solution heat treatment and artificial aging). It turned out that AlSi7Mg alloy after simultaneous barbotage refining with argon and grain refining with titanium-boron and modified with strontium was characterised with lower values of representative microstructure parameters (SDAS - secondary dendrite arm spacing, lambda(E), l(max)) and lower value of the porosity ratio compared to the alloy refined traditionally with Dursalit EG 281 and grain refining with titanium-boron and modified with sodium. The higher values of mechanical properties and fatigue strength parameters were obtained for the alloy simultaneously barbotage-refined with argon and grain refining with titanium-boron and modified with strontium.

关键词： AlSi7Mg0.3 alloy Refining and modification Cooling rate microstructure parameters Usable properties

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Parametric identification of crystals having a cubic lattice with negative Poisson's ratios

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JOURNAL OF APPLIED MECHANICS AND TECHNICAL PHYSICS 2015年第6期56卷 1015-1022页

作者： Erofeev, V. I. Pavlov, I. S. Russian Acad Sci Inst Problems Mech Engn Nizhnii Novgorod 603024 Russia Lobachevsky State Univ Nizhni Novgorod Res Inst Mech Nizhnii Novgorod 603950 Russia

A two-dimensional model of an anisotropic crystalline material with cubic symmetry is considered. This model consists of a square lattice of round rigid particles, each possessing two translational and one rotational degree of freedom. Differential equations that describe propagation of elastic and rotational waves in such a medium are derived. A relationship between three groups of parameters is found: second-order elastic constants, acoustic wave velocities, and microstructure parameters. Values of the microstructure parameters of the considered anisotropic material at which its Poisson's ratios become negative are found.

关键词： crystal with a cubic lattice negative Poisson's ratios microstructure parameters parametric identification

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Effect of film thickness on microstructure parameters and optical constants of CdTe thin films

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JOURNAL OF ALLOYS AND COMPOUNDS 2009年第1-2期482卷 400-404页

作者： Shaaban, E. R. Afify, N. EI-Taher, A. Qassim Univ Dept Phys Fac Sci Buridah 51452 Saudi Arabia Assiut Univ Dept Phys Assiut Egypt Al Azhar Univ Fac Sci Dept Phys Assiut Egypt

Different thickness of cadmium telluride (CdTe) thin films was deposited onto glass substrates by the thermal evaporation technique. Their structural characteristics were studied by X-ray diffraction (XRD). The XRD experiments showed that the films are polycrystalline and have a zinc-blende (cubic) structure. The microstructure parameters, crystallite size and microstrain were calculated. It is observed that the crystallite size increases and microstrain decreases with the increase in the film thickness. The fundamental optical parameters like band gap and extinction coefficient are calculated in the strong absorption region of transmittance and reflectance spectrum. The possible optical transition in these films is found to be allowed direct transition with energy gap increase from 1.481 to 1.533 eV with the increase in the film thickness. It was found that the optical band gap increases with the increase in thickness. The refractive indices have been evaluated in transparent region in terms of envelope method, which has been suggested by Swanepoul in the transparent region. The refractive index can be extrapolated by Cauchy dispersion relationship over the whole spectral range, which extended from 400 to 2500 nm. It is observed that the refractive index, n increases on increasing the film thickness up to 671 nm and then the variation of n with higher thickness lie within the experimental errors. (C) 2009 Elsevier B.V. All rights reserved.

关键词： CdTe Semiconductors Thin films microstructure parameters Optical constants

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Optical constants and fitted transmittance spectra of varies thickness of polycrystalline ZnSe thin films in terms of spectroscopic ellipsometry

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JOURNAL OF ALLOYS AND COMPOUNDS 2013年 563卷 274-279页

作者： Shaaban, E. R. Al Azhar Univ Dept Phys Fac Sci Assiut 71542 Egypt

Different thickness of Zinc selenide (ZnSe) thin films were deposited onto glass substrates by the thermal evaporation technique. Their structural characteristics were studied by X-ray diffraction (XRD). The microstructure parameters, crystallite size and microstrain were calculated. The optical constants (n,k) and film thicknesses of ZnSe thin films were obtained by fitting the ellipsometric parameters (psi and Delta) data using three layer model systems in the wavelength range 300-1100 nm. It is found that the refractive index, n increases with the increase of the film thickness. The possible optical transition in these films is found to be allowed direct transitions. The optical energy gap increase with increasing the film thickness in a narrow range. The experimental transmittances spectrum can be fitted in terms Murmann's exact equation using the modeled thickness and optical constants obtained spectroscopic ellipsometry model. (c) 2013 Elsevier B.V. All rights reserved.

关键词： ZnSe thin film microstructure parameters Spectroscopic ellipsometry Band gap Transmittance spectra

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A MATHEMATICAL MODEL FOR INVESTIGATION OF NONLINEAR WAVE PROCESSES IN A 2D GRANULAR MEDIUM CONSISTING OF SPHERICAL PARTICLES

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COMPOSITES-MECHANICS COMPUTATIONS APPLICATIONS 2013年第3期4卷 239-255页

作者： Erofeev, V. I. Pavlov, I. S. Leontiev, N. V. Russian Acad Sci Mech Engn Res Inst Nizhnii Novgorod Russia

A two-dimensional model of a crystalline (granular) medium, representing a square lattice consisting of elastically interacting spherical particles with three translational and three rotational degrees of freedom, is discussed. Nonlinear differential equations, describing the propagation and interaction of various types of waves in such medium, are derived. An analytical dependence of the coefficients of these equations on the microstructure parameters is found. When only the motion of the particles in the lattice plane is considered, the rotational degree of freedom of particles in the region of low frequencies can be ignored, and the obtained system degenerates into a two-mode system. It is shown that in a one-dimensional case the latter model allows a soliton solution on sheer deformation under the conditions of longitudinal static deformation.

关键词： granular medium structural modeling microstructure parameters soliton solution

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Kinetics of Mechanical Alloying, Mechanical Properties of Micro and Nanostructural Al-C Systems

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HIGH TEMPERATURE MATERIALS AND PROCESSES 2012年第4-5期31卷 359-369页

作者： Besterci, Michal Suelleiova, Katarina Velgosova, Oksana Slovak Acad Sci Inst Mat Res Kosice Slovakia Tech Univ Kosice Fac Met Dept Mat Sci Kosice 04200 Slovakia

A method of mechanical alloying process is described. Carbon transformation to Al4C3 is characterized within the different heat treatment schedules and nine commercial carbon powders are tested. The micromechanism of carbon incorporation into the metallic powder, and its compacting are described. The influence of dispersed carbides on mechanical properties is evaluated together with the influence of deformation on microstructure and properties. It was proved that the transformation efficiency of carbon to Al4C3 by heat treatment of aluminium with the porous furnace black and electrographite is higher than that of the hard cracked graphite. microstructure changes consisted of the fracture processes and welding of the particles with incorporation of C phase and forming of final granules. The dispersed phase Al4C3 particle size was measured on thin foil structures, and it was constant and as small as 30 nm. The particle size was influenced neither by the carbon type nor by the heat treatment technology applied. Subgrain size measured in the range of 100 grains in thin foils depended on the carbon type, as well. It ranged from 0.3 to 0.7 mu m. Using a DSI (depth sensing indentation technique), the Martens hardness, indentation modulus E and deformation work W for Al matrix and Al4C3 particles have been measured. The temperature dependence of ductility, and reduction of area in the temperature range of 623-723 K and strain rate of 10(-1) s(-1), indicated a considerable increase of these properties. In a case when the volume fraction of Al4C3 changes from lower to higher, the grain rotation mechanism dominates instead of the grain boundary sliding. The comparison of the tensile test results and changes in fracture for the Al-Al4C3 system at two temperatures and two strain rates is summarized. The dependence of the minimum deflection rate on the applied force as well as the dependence of the time to fracture on the applied force for two temperature levels (623 and 723 K) b

关键词： aluminium-graphite powder system mechanical alloying carbon to Al4C3 transformation compacting microstructure parameters mechanical properties indentation hardness creep characteristics

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