INVESTIGATION OF ANTI-PLANE SHEAR BEHAVIOR OF TWO COLLINEAR CRACKS IN PIEZOELECTRIC MATERIALS BY A NEW METHOD

In this paper, the interaction between two collinear cracks inpiezoelectric materials under anti-plane shear loading wasinvestigated for the impermeable crack face conditions. By using theFourier transform, the problem can be solved with two pairs of tripleintegral equations. These equations are solved using Schmidt'smethod. This process is quite different from that adopted previously.This makes it possible to understand the two collinear cracksinteraction in piezoelectric materials.

DYNAMIC FRACTURE MECHANICS ANALYSIS FOR COMPOSITE MATERIAL WITH MATERIAL NON-HOMOGENEITY IN THICKNESS DIRECTION

The problem considered here is the response of a non-homogeneouscomposite material containing some cracks subjected to dynamicloading. It is assumed that the composite material is or- thotropicand all material properties depend only on the coordinate y (alongthe thickness direcion). In the analysis, the elastic region isdivided into a number of plies of infinite length. The materialproperties are taken to be constants for each ply. By utilizing theLaplace transform and Fourier transform technique, the generalsolutions for plies are derived.

COUPLED THERMAL/MECHANICAL ANALYSIS FOR THE FRACTURE OF FUNCTIONALLY GRADED MATERIALS UNDER TRANSIENT THERMAL LOADING

A comprehensive treatment of fracture of functionally gradedmaterials (FGMs) is provided. It is assumed that the materialproperties depend only on the coordinate perpendicular to the cracksurface And vary continuously along the crack faces. By using alaminated composite plate model to simulate the ma- Terialnon-homogeneity, an algorithm for solving the system based on Laplacetransform and Fourier transform Techniques is presented. Unlikeearlier studies that considered certain assumed propertydistributions and a Single crack problem, the current investigationstudies multiple crack problem in the FGMs with arbitrarily Varyingmaterial properties. Transient thermal stresses are presented.

DYNAMIC RESPONSE FOR FUNCTIONALLY GRADED MATERIALS WITH PENNY-SHAPED CRACKS

This paper provides a method for studying the penny-shaped cracksconfiguration in functionally graded material(FGM)structuressubjected to dynamic or steady loading. It is assumed that the FGMare transversely isotropic and all the material properties onlydepend on the axial coordi- nate z. In the analysis, the elasticregion is treated as a number of layers. The material properties aretaken to be constants for each layer. By utilizing the Laplacetransform and Hankel transform tech- nique, the general solution forthe layers are derived.

INVESTIGATION OF THE SCATTERING OF ANTI-PLANE SHEAR WAVES BY TWO GRIFFITH CRACKS USING THE NON-LOCAL THEORY

In this paper, the scattering of harmonic antiplane shear waves bytwo finite cracks is studied using the non-local theory. The Fouriertransform is applied and a mixed boundary value prob- lem isformulated. Then a set of triple integral equations is solved using anew method, namely Schimidt's method. This method is more exact andmore reasonable than Erigen's for solving this Kind of problem. Theresult of the stress near the crack tip was obtained. Contrary to theclassical elas- Ticity solution, it is found that no stresssingularity is present at the crack tip, which can explain theProblem of macroscopic and microscopic mechanics.

TiC Fe cermets fabricated by SHS

The dense TiC Fe cermets were produced by self propagating high temperature synthesis and pseudo hot isostatic pressing(SHS/PHIP). The influence of Fe content on the combustion temperature, combustion velocity, density and microstructure of products was studied. The composition and microstructure of the product were analyzed. The results showed that the cermet consists of quasi spherical TiC particles and Fe binder phases. A thin diffusion layer was found between Fe binder phase and TiC particle. In the range of 10%～20% Fe content, the combustion temperature and velocity decrease more slowly than the other contributions.

THE SCATTERING OF HARMONIC ELASTIC ANTI-PLANE SHEAR WAVES BY A FINITE CRACK IN INFINITELY LONG STRIP USING THE NON-LOCAL THEORY

In this paper, the scattering of harmonic anti-plane shear wavesby a finite crack in infinitely long strip is studied using thenon-local theory. The Fourier transform is applied and a mixedboundary value problem is formulated. Then a set of dual integralequations is solved using the Schmidt method instead of the first orthe second integral equation method. A one-dimensional non-localkernel is used instead of a two-di- mensional one for the anti-planedynamic problem to obtain the stress occurring at the crack tips.Contrary to the classical elasticity solution, it is found that nostress singularity is present at the crack tip. The non-local dynamicelastic solutions yield a finite hoop stress at the crack tip, thusallowing for a fracture criterion based on the maximum dynamic stresshypothesis. The finite hoop stress at the crack tip depends on thecrack length, the width of the strip and the lattice parameters.

盐雾条件下NiCrAl涂层的耐腐蚀性研究

采用大气等离子喷涂工艺在Ni基高温合金上制备NiCrAl涂层,并研究了该涂层在盐雾腐蚀和氧化条件下的耐腐蚀性能。通过对NiCrAl涂层盐雾腐蚀前后的极化曲线分析,可知NiCrAl涂层盐雾腐蚀后的腐蚀电位变得更负,腐蚀电流密度变得更大,说明经过盐雾腐蚀后的NiCrAl涂层的耐腐蚀性明显下降。由SEM观察可知,NiCrAl涂层经过盐雾腐蚀后表面和内部都出现了大量的裂纹,组织变得疏松,遭到严重腐蚀,涂层失去保护能力。经EDX分析可知,腐蚀产物的化学通式为MexOyClz。经过预氧化的NiCrAl涂层由于形成了θ-Al2O3膜,耐腐蚀性能增强。