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Almost all solid surfaces have roughness on different length scales, from macro, micro to nano. In the conventional fractal contact model, the macroscopic Hertzian contact theory is employed to predict the contact load-area relation for all sizes of contact spots. However, when the contact radius of an asperity shrinks to nanometers, surface tension may greatly alter the contact behavior. In the present paper, we address surface effects on the contact between a rigid sphere and an elastic half space, and we demonstrate that the contact load-area relation is size-dependent, especially for nanosized asperities. Then, the refined contact relation is incorporated into the Majumdar-Bhushan fractal contact model. It is found that the presence of surface tension requires higher load than the conventional fractal contact model to generate the same real contact area. [ABSTRACT FROM AUTHOR]

An approximate continuum theory is developed to effectively handle the problem of interaction between dislocations and inhomogeneity of any shape and properties. The inhomogeneity is, based on the Eshelby equivalent inclusion theory, equivalent to a homogenous one with a transformation strain. The interaction force between dislocation and the inhomogeneity can then be evaluated from the work done by the dislocation stress field during the transformation. The proposed continuum theory is applicable to a variety of inhomogeneities, such as pore, gas bubble, shear band and plastically deformed zone. It can be reduced to the classical continuum theory for some special cases. [ABSTRACT FROM AUTHOR]

Effects of surfaces/interfaces become prominent in micro- and nanosized materials and devices. In the present paper, the diffraction of plane harmonic compressional waves (P wave) by a spherical nanoinclusion is studied theoretically using the surface/interface elasticity theory. The results demonstrated that when the inclusion size shrinks to nanometers, surface/interface elasticity plays a significant role in the diffraction of elastic waves. For incident waves of different frequencies, the interface effects on the dynamic stress concentration around the spherical inclusion are examined in detail. [ABSTRACT FROM AUTHOR]

The residual stresses due to high-temperature processing in micromultilayer ceramic capacitors (MLCCs) with various thicknesses and numbers of dielectric ceramic layers were investigated by using a three-dimensional elastoplastic finite element model with temperature-dependent material properties taken into account. For comparison, an explicit analytical solution for the in-plane residual stress in the dielectric ceramic layer was derived. Both the numerical results and the analytical model showed that the thickness ratio of the dielectric layer to electrode layer has a dominant impact on the residual stress states. There exists a critical thickness for the dielectric ceramic layer in MLCCs in the case of a given thickness of the electrode layer, below which both high tensile out-of-plane stresses and high compressive in-plane stresses could cause the cracking of the brittle dielectric layers near the electrode tips and/or the debonding of the electrode/dielectric interface. [ABSTRACT FROM AUTHOR]

Based on the surface elasticity theory, we examined the effects of surface stresses on nanosized contact problems. The Fourier integral transform method is adopted to derive the general solution for the contact problem under pressure. As two examples, the deformations induced, respectively, by a uniform distributed pressure and a concentrated force are analyzed in detail. The results indicate some interesting characteristics in contact mechanics, which are distinctly different from those in classical elasticity theory. Both the contact normal stress and the deformation gradient on the deformed surface vary smoothly across the loading boundary as a result of surface stress. In addition, the indent depth and the maximum normal contact stress depend strongly on the surface stress for nanoindentation. [ABSTRACT FROM AUTHOR]

A large number of porcelain shards were unearthed at the Hehuaxin and Silongkou kilns around the Shanglin Lake, Ningbo, China, some of which had clear stratification to enable the determination of the date of firing. With the purpose of studying the elemental composition in different cultural periods and between kilns, the chemical compositions of 43 typical shards from these two kilns were determined by energy‐dispersive X‐ray fluorescence (EDXRF). The results show that the mean contents of K2O, CaO and MnO in the glaze fluctuate in different cultural periods at the Hehuaxin kiln, but not systematically. Principal component analysis (PCA) indicates that samples from the Five Dynasties and the Northern Song dynasty are similar to each other. This shows continuity in the raw materials and firing technology between the two dynasties. Comparing the mise type wares from the Hehuaxin and Silongkou kilns in the Northern Song dynasty, we found that MnO and ZrO2 in the glaze can be used as fingerprinting elements to distinguish between samples from these two sites. In spite of this, their chemical compositions are broadly similar. Thus, perhaps, their chemical compositions can be taken as typical for those of the mise type wares produced around the Shanglin Lake. [ABSTRACT FROM AUTHOR]

There is a generally accepted view that there is an obvious distinction between proto‐porcelain and stamped stoneware. However, some early shards unearthed from the Dongtiaoxi region (northern Zhejiang) inspire people to rediscuss the relationship between them, because it is difficult to identify them as proto‐porcelain or stamped stoneware. In this work, we have collected samples from three of the earliest kiln sites (Piaoshan, Beijiashan and Nanshan) in the Dongtiaoxi region. We have analysed the chemical composition, firing temperature and phase composition of the samples. Comparing samples from the three kiln sites, we find that, from Piaoshan and Beijiashan to Nanshan, there has been progression in the manufacturing technology. The Shang proto‐porcelain and the stamped stoneware from Nanshan have similar raw materials, firing temperatures and body phase compositions—and they have obviously different decorative appearances, such as glazing or stamping. For ceramics from Piaoshan and Beijiashan, there is no clear distinction between glazed and unglazed samples. We believe that in the Dongtiaoxi region, the difference in the decoration between proto‐porcelain and stoneware became obvious up to the time of the Nanshan production but that, subsequently, two different paths for the development of high‐fired ceramics began to diverge. [ABSTRACT FROM AUTHOR]

Samples of celadon were collected from the Altar Guan Kiln in Hangzhou, and from the Xiaomeizhen and Xikou Kilns, two subordinate kilns of the Longquan Kiln producing black‐body celadon called Literature Ge. Both the elemental contents in the sample bodies and the glaze were measured. The results reveal that the sample bodies contain fingerprint information for provenance, while this was lost in the glaze during the production process. The TiO2, MnO and Rb2O contained in the bodies are fingerprints to distinguish between celadons from the Xiaomeizhen and Xikou Kilns. In the Altar Guan Kiln, some low‐TiO2 samples were found and their body colour is much lighter than some others, but they do not differ with regard to iron content. This indicates that both titanium and iron are indispensable for the blackness of the bodies: they may react to form some black minerals during the firing process. Ultimately, samples from the Literature Ge and Altar Guan Kilns differ in their body constituents. Principal component analysis reveals that the samples can be divided into two groups, corresponding to the two different areas. [ABSTRACT FROM AUTHOR]