The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform

Yongqiang Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Vibration of Elastic Functionally Graded Thick Rings
    Shock and Vibration, 2020
    Co-Authors: Guang-hui Xu, Huaiwei Huang, Yongqiang Zhang
    Abstract:

    The free vibration behaviors of functionally graded rings were investigated theoretically. The material graded in the thickness direction according to the power law rule and the rings were assumed to be in Plane stress and Plane Strain states. Based on the first-order shear deformation theory and the kinetic relation of von Karman type, the frequency equation for free vibration of functionally graded ring was derived. The derived results were verified by those in literatures which reveals that the present theory can be appropriate to predict the free vibration characteristics for quite thick rings with the radius-to-thickness ratio from 60 down to 2.09. Comparison between the Plane stress Case and the Plane Strain Case indicates a slight difference. Meanwhile, the effects of the structural dimensional parameters and the material inhomogeneous parameter are examined. It is interesting that the value of the logarithmic form of vibration frequency is inversely proportional to the logarithmic form of the radius-to-thickness ratio or the mean radius.

  • stability of hydrostatic pressured fgm thick rings with material nonlinearity
    Applied Mathematical Modelling, 2017
    Co-Authors: Huaiwei Huang, Yongqiang Zhang
    Abstract:

    Abstract Buckling behaviors of elastoplastic ceramic/metallic functionally graded material (FGM) rings are investigated by using the first order shear deformation theory. The hydrostatic-pressured rings are assumed to be in both the Plane-stress Case and the Plane-Strain Case, which lead respectively to a uniaxial and a biaxial elastoplastic stress states in prebuckling stage. A uniform Strain hypothesis helps to deal with the elastoplastic stress states. By introducing in the graded material properties, the constitutive model of FGMs is formulated under the framework of J 2 deformation theory. By considering the kinetic relations of von-Karman type and employing the principle of virtual displacement, the equilibrium equations and the buckling governing equations of FGM circular rings are formulated, and the analytical solution of the anisotropic rings is obtained. Finally, the elastoplastic buckling problem is numerically solved through a semi-analytical method, which is proposed to seek the real circumferential Strain of FGM rings at the buckling point and determinate the elastoplastic buckling critical hydrostatic pressure. The effects of the inhomogeneous and geometrical parameters on the buckling critical load and the position of the elastoplastic interface are discussed. Results show that, in both the Plane-stress and the Plane-Strain Cases, the elastoplastic critical loads are generally lower than their elastic counterparts due to material flow, and the Plane-Strain critical load is generally larger than the Plane-stress one. The elastoplastic critical load does not always decrease monotonously with the increase of the inhomogeneous parameters, which is quite different from their elastic counterparts.

  • Effect of porosity on the properties of Strain localization in porous media under undrained conditions
    International Journal of Solids and Structures, 2002
    Co-Authors: Yongqiang Zhang, Mao-hong Yu
    Abstract:

    Abstract Within the general framework of mixture theory and by introducing the fictitious “fluid phase” as a mixture of a liquid and a gas, the conditions for localization of deformation into a shear band in the incremental response of partially saturated and fully saturated elastic–plastic porous media under undrained conditions are derived. The effect of porosity is included in the derivation. The explicit analytical expressions of the direction of shear band initiation and the corresponding hardening modulus of the porous media for the Plane Strain Case are deduced, and a parametric analysis is made of the influence of the porosity on the properties of Strain localization based on Mohr–Coulomb yield criterion. It is found that the dependence of the shear banding properties of partially saturated porous media on the porosity is related to the stress states and Poisson's ratio. However, the properties of the Strain localization for the fully saturated porous media are almost independent of Poisson's ratio. Finally, on the basis of Mohr–Coulomb yield criterion, some solutions of the shear banding orientation for water-saturated granular materials are obtained, which are proved to be in good agreement with the experimental results reported by other researchers.

Huaiwei Huang - One of the best experts on this subject based on the ideXlab platform.

  • Vibration of Elastic Functionally Graded Thick Rings
    Shock and Vibration, 2020
    Co-Authors: Guang-hui Xu, Huaiwei Huang, Yongqiang Zhang
    Abstract:

    The free vibration behaviors of functionally graded rings were investigated theoretically. The material graded in the thickness direction according to the power law rule and the rings were assumed to be in Plane stress and Plane Strain states. Based on the first-order shear deformation theory and the kinetic relation of von Karman type, the frequency equation for free vibration of functionally graded ring was derived. The derived results were verified by those in literatures which reveals that the present theory can be appropriate to predict the free vibration characteristics for quite thick rings with the radius-to-thickness ratio from 60 down to 2.09. Comparison between the Plane stress Case and the Plane Strain Case indicates a slight difference. Meanwhile, the effects of the structural dimensional parameters and the material inhomogeneous parameter are examined. It is interesting that the value of the logarithmic form of vibration frequency is inversely proportional to the logarithmic form of the radius-to-thickness ratio or the mean radius.

  • stability of hydrostatic pressured fgm thick rings with material nonlinearity
    Applied Mathematical Modelling, 2017
    Co-Authors: Huaiwei Huang, Yongqiang Zhang
    Abstract:

    Abstract Buckling behaviors of elastoplastic ceramic/metallic functionally graded material (FGM) rings are investigated by using the first order shear deformation theory. The hydrostatic-pressured rings are assumed to be in both the Plane-stress Case and the Plane-Strain Case, which lead respectively to a uniaxial and a biaxial elastoplastic stress states in prebuckling stage. A uniform Strain hypothesis helps to deal with the elastoplastic stress states. By introducing in the graded material properties, the constitutive model of FGMs is formulated under the framework of J 2 deformation theory. By considering the kinetic relations of von-Karman type and employing the principle of virtual displacement, the equilibrium equations and the buckling governing equations of FGM circular rings are formulated, and the analytical solution of the anisotropic rings is obtained. Finally, the elastoplastic buckling problem is numerically solved through a semi-analytical method, which is proposed to seek the real circumferential Strain of FGM rings at the buckling point and determinate the elastoplastic buckling critical hydrostatic pressure. The effects of the inhomogeneous and geometrical parameters on the buckling critical load and the position of the elastoplastic interface are discussed. Results show that, in both the Plane-stress and the Plane-Strain Cases, the elastoplastic critical loads are generally lower than their elastic counterparts due to material flow, and the Plane-Strain critical load is generally larger than the Plane-stress one. The elastoplastic critical load does not always decrease monotonously with the increase of the inhomogeneous parameters, which is quite different from their elastic counterparts.

Andreas Ochsner - One of the best experts on this subject based on the ideXlab platform.

  • Elastic Material Behavior
    Continuum Damage and Fracture Mechanics, 2015
    Co-Authors: Andreas Ochsner
    Abstract:

    This chapter reviews the basics of elastic material behavior. Starting from simple load Cases, i.e. uniaxial tension, pure shear and hydrostatic compression, basic material parameters are derived from experimental results. The next part presents the three-dimensional constitutive law for isotropic and linear-elastic material behavior. The chapter closes with two important Cases of two-dimensional formulations, i.e. the Plane stress and the Plane Strain Case.

  • 2d modelling of a thin elasto plastic interphase between two different materials Plane Strain Case
    Composite Structures, 2007
    Co-Authors: Gennady Mishuris, Andreas Ochsner
    Abstract:

    A thin soft elasto-plastic interphase between two different media is under consideration. The intermediate layer is assumed to be of infinitesimal thickness and is modelled by non-linear transmission conditions which incorporate the elasto-plastic material behaviour of the layer. FEM analysis of a bimaterial structure with such an imperfect elasto-plastic interface shows the efficiency of the approach and illustrates some restrictions of its application.

Gennady Mishuris - One of the best experts on this subject based on the ideXlab platform.

Pradeep R. Guduru - One of the best experts on this subject based on the ideXlab platform.

  • Biologically Inspired Mechanics of Wavy Surface Adhesion
    Experimental Analysis of Nano and Engineering Materials and Structures, 2020
    Co-Authors: Pradeep R. Guduru
    Abstract:

    Inspired by the attachment ability of insects with smooth pads to vertical walls and ceilings, the mechanics of detachment of a rigid solid from an elastic wavy surface has been analyzed for the axisymmetric Case of a sphere and the Plane Strain Case of a cylinder [1]. Due to the qualitative similarities, the discussion was limited to the axisymmetric Case only. The load-displacement curve for a sphere indenting a wavy flat surface is shown in Fig. 1, in which the load P is normalized with the JKR pull-off force P jxr and the approach displacement h is normalized with the waviness amplitude λ.

  • Detachment of a rigid solid from an elastic wavy surface : Experiments
    Journal of The Mechanics and Physics of Solids, 2007
    Co-Authors: Pradeep R. Guduru, C. Bull
    Abstract:

    Abstract The mechanics of detachment of a rigid solid from an elastic wavy surface has been analyzed in a recent article, in which the axisymmetric Case of a sphere and the Plane Strain Case of a cylinder were considered. Due to the qualitative similarities, the discussion was limited to the axisymmetric Case only. It was shown that the surface waviness makes the detachment process proceed in alternating stable and unstable segments and each unstable jump dissipates mechanical energy. As a result, the external work and the peak force required to separate a wavy interface are higher than the corresponding values for a flat interface, i.e., waviness causes interface toughening as well as strengthening. In this paper, a systematic experimental investigation is presented which examines the above theoretical analysis, by measuring adhesion between a “rigid” wavy punch and a soft “elastic” material, which is a block of gelatin here. The observed increase in adhesion due to waviness closely agrees with the theoretical predictions within the experimental and material uncertainties. The experiments not only validate the theory, but also demonstrate that adhesion of a soft material can be substantially enhanced by topographic optimization alone, without modifying the surface chemistry.