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The paper deals with interface behavior of bimaterial ceramic-metal composites under dynamic time-harmonic load, The first plate is precracked with a normal crack touching the interface between the plates. It is assumed that the respective restriction for the ratio of energy release rates of the plates allowing the occurrence of an interface single delamination before the initiation of the normal crack in the second plate is satisfied. The growth of interface delamination is not considered. The used approximate shear- lag dynamic approach gives a possibility to obtain solutions in a closed form for axial and shear stresses of the structure. At an elastic- brittle interface behavior theoretical predictions for single debond length of two bimaterial structures are calculated. The parametric analysis reveals the sensitivity of the interface single debond length and shear stress to the type of bimaterial structure and to the characteristics of the dynamic load--in particular its frequency and amplitude. All results are illustrated in figures and tables and are discussed, DOI: 10.1061/(ASCE)EM.1943-7889.0000155 CE Database subject headings: Cracking; Shear lag; Bonding; Delaminating; Plates; Dynamic loads, Author keywords: Dynamics of bimaterial cracked plate; Shear lag model; Interface elastic-brittle delamination; Single debond length.

Colloidal coatings, such as paint, are all around us. However, we know little about the mechanics of the film-forming process because the composition and properties of drying coatings vary dramatically in space and time. To surmount this challenge, we extend traction force microscopy to quantify the spatial distribution of all three components of the stress at the interface of two materials. We apply this approach to image stress near the tip of a propagating interface crack in a drying colloidal coating and extract the stress intensity factor. fracture mechanics | colloids | ceramics doi/ 10.1073/pnas.1005537107

A[l.sub.2][O.sub.3]-Zr[O.sub.2] ceramics containing 5-50 mol% Zr[O.sub.2] were prepared by solid state reaction method. The bulk density, average grain size and microhardness of A[l.sub.2][O.sub.3]-Zr[O.sub.2] ceramics system as function of Zr[O.sub.2] content were investigated. The dense A[l.sub.2][O.sub.3] ceramics were successfully by means of carefully control processing parameters that include sintering temperature and heating/cooling rates. These ceramics with higher Zr[O.sub.2] content was obtained high bulk densities and small grain sizes. However, the high hardness values were exhibited from A[l.sub.2][O.sub.3] ceramics with dopants Zr[O.sub.2] between 1-10mol% and its tend to decrease with concentration of Zr[O.sub.2]. It can be found that the fast heating/cooling rates are controlled grain growth and obtained high hardness in materials. The results gave good correlation between stoichiometry characteristics, heating/cooling rates in sintering and microstructure of fabricated dense and mechanical properties. Key words: A[l.sub.2][O.sub.3]-Zr[O.sub.2] ceramics, microhardness, heating/cooling rates, sintering, INTRODUCTION The most widely used ceramic materials are alumina, A[l.sub.2][O.sub.3] and zirconia, Zr[O.sub.2], because of their excellent bio-compatibility. The main advantage of A[l.sub.2][O.sub.3] is its high hardness and wear resistance, [...]

Numerical and analytical simulations of projectiles penetrating brittle materials such as ceramics and glasses are a very challenging problem. The difficulty comes from the fact that the yield surface of brittle materials is not well characterized (or even defined), and the failure process may change the material properties. Recently, some works have shown that it is possible to characterize and find the constitutive equation for brittle materials using a confined compression test, i.e., a test where a cylindrical specimen, surrounded by a confining sleeve, is being compressed axially by a mechanical testing machine. This paper focuses on understanding the confined compression test by presenting an analytical model that explicitly solves for the stresses and strains in the sample and the sleeve, assuming the sleeve is elastic and the specimen is elastoplastic with a Drucker-Prager plasticity model. The first part of the paper briefly explains the experimental technique and how the stress-strain curves obtained during the test are interpreted. A simple and straight forward approach to obtain the constitutive model of the material is then presented. Finally, a full analytical model with explicit solution for displacements, strains, and stresses in the specimen and the sleeve is described. The advantage of the analytical model is that it gives a full understanding of the test, as well as information that can be useful when designing the test (e.g., displacements of the outer radius of the specimen). [DOI: 10.1115/1.2775501]

The lamellate structure of clay and the extrusion forming process cause terra cotta ceramic's anisotropic elastic behavior at low strain and may induce gradients of macroscopic mechanical properties. Among other techniques, strain measurements obtained through digital image correlations were used to locally characterize transverse isotropic elastic behavior. Kinematic field measurements on small specimens were also compared with fields derived from three-dimensional finite element computations in order to check the consistency of the local characterization procedure. DOI: 10.1061/(ASCE)0899-1561 (2007) 19:8(642) CE Database subject headings: Mechanical properties; Clays; Measurement; Construction materials.

The authors have carried out extensive measurements of electron triboemission from the scratching of ceramics and semiconductors that are briefly summarized in this paper. Analysis of the frequency-domain distribution of typical triboemission count-pulse outputs suggested that their occurrence is not Poisson's (e.g., it is not random). This paper presents a study on the hypothesis of deterministic-chaos origin for triboemission data. Electron triboemission outputs from the ceramics alumina, sapphire, silicon nitride, and the semiconductors Si and Ge are analyzed by means of extracting deterministic-chaos metrics. The results suggest that the low-level electron-emission components may be described by multiplicative processes of random initiation, while the superimposed large burst-type components may be of deterministic origin. [DOI: 10.1115/1.2736709] Keywords: triboemission, exoemission, ceramics, randomness

The article evaluates the use of lower-cost inorganic polymers and ceramic reinforcement materials for wind-and-react insulation materials. Findings reveal that the reinforcement materials provide increased stiffness, thermal conductivity, compression, and shear strengths necessary for magnet applications.

The study investigates the peculiarities of high-pressure oxygenation of the melt-textured Y[Ba.sub.2][Cu.sub.3][O.sub.x]-based thin-walled ceramics (MT-YBCO). The analysis shows that these ceramics acquire a higher microhardness after oxygenation.

The elastic properties of ceramics and a mix of minerals can be calculated in a simple way including some properties of the interfaces between grains. While the Hashin Shtrikman averaging method has bounds, which are strictly correct for many realistic physical conditions, one finds empirical data which lie outside these bonds. One possible interpretation is that the scaling of the volume proportions in mineral assemblies is not truly represented by the nominal volume proportionfof each phase. It is argued that interfacial effects scale with f(1-f). In the case of certain assemblies, it is shown that the scaling is entirely with f rather than f. For intermediate cases, a more realistic scaling replaces f in the relevant averaging schemes by f(1-S) + S [f.sup.2] where S weighs the effect of the non-linearities in the volume expansion of the averaging schemes. Keywords: Compressibility, mechanical properties, elastic moduli, surfaces

Byline: R. Marinkovic-Neducin, J. Ranogajec, V. Mihalj The critical phase in production of specific ceramic materials for hydraulic fracturing in oil/gas production - proppants - is considered to be the formation of high green density spheres of defined diameter (0.4-1.25 mm) from the complex raw material mixture. The degree of sphericity and roundness, as well as the mechanical strength of proppants dependent on the physico-chemical characteristics of the starting powder (multi-component system) and on the procedure and parameters of sphere formation. Two systems, based on alumina and bauxite, both in combination with clay and feldspar, have been investigated as candidate mixtures for intermediate strength/intermediate density proppant (ISP) production. It has been shown that in obtaining the optimal properties of final system-proppant, good packing in green state is less important than the interaction of plastic and non-plastic components during sintering in the closed system. The physico-chemical properties of the liquid phase seem to play a dominant role in obtaining the desired microstructure and resulting mechanical properties.

The conventional solid-state reaction method is employed to explain the fabrication, as well as the various properties of the SrTi[O.sub.3] ceramics. These ceramics are shown to exhibit extremely high-temeprature dielectric relaxation caused due to the presence of oxygen vacancies inside them.

Byline: Yingge Dong, Jinlong Yang Silicon nitride ceramics were fabricated using submicron Si3N4 powder and nano-Si3N4, adding Al2O3 and Y2O3 by isostatic pressing and SSN. In the paper, the dispersion of nano-Si3N4 powder, the effect of different nano-Si3N4 concentrations on Si3N4 ceramic mechanical properties, application performances and nano-Si3N4 dispersion are discussed. The results demonstrated that the dispersion effect of ethanol was better than water as solvent when PEG was the dispersant agent and the time was 40 min by a supersonic instrument. Flexural strength, hardness and fracture toughness of the specimens were the highest when the content of nano-Si3N4 was 3% by weight.

Byline: Ming Yue, Jinlong Yang, Xiaoqing Xi, Yong Huang Microbeads produced by colloidal injection moulding own high quality and performance. In this paper, friction and wear properties of the microbeads were studied. The effects of surface roughness, degassing of slurries, and water lubrication on the wear properties were discussed. The results show that the smoother the surface is, the better the wear resistance of the ceramic; the process of degassing of slurries in the moulding procedure improves the wear resistance of the ceramics; high load leads to severe wear under both dry sliding condition and water lubrication, and water acts as lubrication and decreases the wear of the ceramics.

A heterodyne Doppler interferometric method is used to measure the longitudinal ac strain response of lead lanthanum zirconate titanate (PLZT) ceramics while varying both the ac and the dc bias electric-field strengths. The results from the temperature and frequency dependence of the dielectric properties of a relaxor ferroelectric have provided insight into other characteristics such as electrostrictive and electro-optic behavior, which are consequences of dipole moments arising from ion displacements.

The microstructures, dielectric properties and ferroelectric relaxor behavior of rare-earth (La, Sm, Eu, Dy, Y) substituted barium zirconium titanate ceramics fabricated via the solid-state reaction method are examined. The doping amount of suitable rare-earth ions are manipulated in order to obtain tunable ferroelectric materials with moderate dielectric constant and low dielectric loss.

Environmentally dependent subcritical crack growth, stress-corrosion cracking and ceramic-metal interfaces are analyzed for the silica glass-copper system. The results are used for understanding the micro-mechanisms that govern stress-corrosion crack growth along ceramic-metal interfaces.