Papers by Author: Yue Sheng Wang

Abstract: Combined with the supercell technique, the plane wave expansion method is used to calculate the band structures for the in-plane wave of the two-dimensional solid-solid phononic crystals with line defects and the random disorders in either radius or location of the scatterers. The influences of the random disorders on the band structures and guided waves will be discussed. Propagation of the wave with one certain frequency in the waveguiding phononic crystals with different disorder degree is studied.

Abstract: The supercell based plane wave expansion method is used to study the effects of random disorders on the band structures of a two-dimensional (2D) solid-fluid phononic crystal. Phononic systems with steel scatterers embedded in a water matrix are calculated in detail. The radius disorder and location disorder are concerned. The influences of the disorder degree on the first band gap are investigated. The localization phenomenon is discussed by computing the displacement fields in the supercell.

Abstract: In this paper, a method based on the displacement-traction map is developed to calculate the bandgaps of transverse waves propagating in a 2D phononic crystal composed of nanosized circular holes in a square lattice. The Young-Laplace equation is employed to take into account of the surface effects of the nanosized holes. Detailed calculations are performed for the system with nanosized circular holes in an aluminum host with or without the surface effect. The result shows that all bands descend with the first bandgap becoming wider due to the existence of the surface effects.

Abstract: In this paper, combined with the supercell technique, the plane wave expansion method is used to calculate the band structures of the two-dimensional phononic crystals with line defects and the random disorders in either radius or location of the scatterers. Phononic systems with plumbum scatterers embedded in an epoxy matrix are calculated in detail. The influences of the random disorder on the band structures of anti-plane waveguiding modes will be discussed. The displacement distributions are calculated to show the wave localization phenomenon. Propagation of the guided wave in the phononic crystals with different disordered degree is studied. The analysis is relevant to the assessment of the influences of manufacture errors on wave behaviors in waveguiding phononic crystals as well as the possible control of wave propagation by intentionally introducing disorders into the systems.

Abstract: This paper deals with the finite frictional contact of a functionally graded coating with considering the effect of Poisson’s ratio. We assume that a functionally graded coated half-space is indented by a rigid spherical punch and that the shear modulus of FGMs varies as exponential function. The whole contact region is divided into the central adhesion zone and the slip annulus. Within the slip annulus, the shear stress is limited by friction. By using the Hankel integral transform technique, the problem is reduced to a set of Cauchy singular integral equations. A numerical method is used to get the contact pressure and tangential tractions in the contact region for different Poisson’s ratio. The results show that the variation of Poisson’s ratio has obvious effect on both normal and tangential tractions. With the increase of ν, the peak value of the normal traction increases and that of the tangential traction decreases.

Abstract: The improved supercell plane wave expansion method is applied to theoretically study the propagation of flexural waves in a ternary locally resonant phononic crystal thin plate with a point defect and linear defects. The thin concrete plate composed of a square array of steel cylinders hemmed around by rubber is considered here. Absolute band gaps in low frequency are obtained. For the point defect, the defect mode is localized around the defect, and the magnitude of the resonant defect mode is strongly dependent on the defect filling fraction, mass density and Young’s modulus of the defect cylinder. For the straight linear defects, several resonant linear defect bands appear inside the absolute band gap. And the displacement distributions show that the flexural waves could well propagate along the linear defects.

Abstract: In this paper, band gaps tunned by material parameters in three-dimensional fluid-fluid sonic crystals are studied. From the basic wave equation, it is found that the material parameters directly determining the three-dimensional sonic band gaps are the mass density ratio and bulk modulus ratio. The calculation of the sonic band gaps is completed by the plane-wave expansion method. The effects of these parameters on sonic band gaps are discussed in details for the simple-cubic (sc), face-centered cubic (fcc) and body-centered cubic (bcc) lattices. The results show that the first potential sonic band gap easily appears at both small mass density ratio and bulk modulus ratio, and becomes wider with both of these two parameters decreasing. The bulk modulus ratio plays a more important role than the mass density ratio in tuning the sonic band gaps. The present analysis can be applied to artificially design band gaps.

Abstract: A quantitative life prediction method has been proposed to evaluate fatigue life during morphological evolution of precipitates in Ni-based superalloys. The method is essentially based on Eshelby’s equivalent inclusion theory and Mori-Tanaka’s mean field method. The shape stability and life prediction are discussed when the external stress and matrix plastic strain are applied. The calculated results show that the fatigue life is closely related with microstructures evolution of precipitates. The magnitude and sign of the external stress and matrix plastic strain have an important effect on fatigue life of Ni-based superalloys during the morphological evolution of precipitates.

Abstract: In this paper, the continuous in-situ observations of the fatigue crack growth in U71Mn and U75V rail steel are made by using the scanning electronic microscope (SEM). The microstructure patterns of cracks under the mode I fatigue loads and quasi-static loads are presented. The results indicate that the short fatigue crack growth in rail steel is a quasi-cleavage fracture. The ductility and the performance of fatigue resistance of U71Mn rail steel are better than those of U75V rail steel.

Abstract: In this paper, a new theoretical model is developed to characterize the damage of the adhesive joint. Elastic modulus of adhesive joints is an important parameter to represent damage characteristics. Based on the fact that the thickness of the adhesive layer is very small, it is reasonable to believe that damage will decrease the tension modulus of the adhesive joint while the compression modulus will keep unchanged. Modeling the adhesive joint as an interface with different modulus in tension and compression, and applying integral transform method, we solve the associated nonlinear boundary problem to obtain the nonlinear ultrasonic waves transmitting through the adhesive layer. With this nonlinear ultrasonic wave, variation of elastic modulus and damage variable of the adhesive layer are thereafter characterized nondestructively by a nonlinear coefficient.