Browsing by Author "Hu, C. N."

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Geometrically induced stress singularities in a piezoelectric body of revolution
(2011-09-01)
Huang, C. S.
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Hu, C. N.
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土木工程學系
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Department of Civil Engineering
An eigenfunction expansion approach is combined with a power series solution technique to establish the asymptotic solutions for geometrically induced electroelastic singularities in a piezoelectric body of revolution, with its direction of polarization not parallel to the axis of revolution. The asymptotic solutions are obtained by directly solving the three-dimensional equilibrium and Maxwell's equations in terms of displacement components and electric potential. When the direction of polarization is not along the axis of revolution, the assumption of axisymmetric deformation that is often made in the published literature is not valid, and the direction of polarization and the circular coordinate variable can substantially affect the singularities. The numerical results related to singularity orders are shown in graphical form for bodies of revolution that comprise a single material (PZT-4 or PZT-5H) or bonded piezo/piezo (PZT-4/PZT-5H) or piezo/isotropic elastic (PZT-4/Al or PZT-5H/Al) materials. This is the first study to present results for the direction of polarization not along the axis of revolution. (C) 2011 Elsevier Ltd. All rights reserved.
Geometrically-induced singularities in functionally graded magneto-electro-elastic wedges
(2014-12-01)
Huang, C. S.
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Hu, C. N.
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土木工程學系
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Department of Civil Engineering
Asymptotic solutions are proposed for geometrically-induced magneto-electro-elastic (MEE) singularities at the vertex of a rectilinearly polarized wedge that is made of functionally graded magneto-electro-elastic (FGMEE) materials. The material properties are assumed to vary along the thickness, of the wedge, and the direction of polarization may not be parallel or perpendicular to the thickness direction. An eigenfunction expansion approach with the power series solution technique and domain decomposition is adopted to establish the asymptotic solutions by directly solving the three-dimensional equations of motion and Maxwell\'s equations in terms of mechanical displacement components and electric and magnetic potentials. Since the direction of polarization can be arbitrary in space, the in-plane components of displacement, electric and magnetic fields are generally coupled with the out-of-plane components. The solutions are presented here for the first time. The correctness of the proposed solutions is confirmed by comparing the orders of MEE singularities with the published results for wedges under anti-plane deformation and in-plane electric and magnetic fields. The proposed solutions are further employed to investigate the effects of the direction of polarization, vertex angle, boundary conditions and material-property gradient index on the MEE singularities in BaTiO3-CoFe2O4 wedges. (C) 2014 Elsevier Ltd. All rights reserved.
Singularity analysis for a magneto-electro-elastic body of revolution
(2013-06-01)
Huang, C. S.
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Hu, C. N.
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土木工程學系
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Department of Civil Engineering
Three-dimensional asymptotic solutions are obtained for magneto-electro-elastic singularities in bodies of revolution that are made of a single magneto-electro-elastic (MEE) material or hi-materials that consist of an MEE material and an elastic material or piezoelectric material. The solutions are obtained by combining an eigenfunction expansion approach with the power series solution method to solve three-dimensional equilibrium equations and Maxwell's equations in terms of mechanical displacement components and electric and magnetic potentials. The MEE material is assumed to be transversely isotropic and its polarization direction is not necessarily parallel to the axis of revolution. The polarization direction, which is not along the axis of revolution, yields and complicates non-axisymmetric solutions. The solutions are validated by comparing the present characteristic values of the asymptotic solutions, which are related to the orders of singularities of stress, electric displacement and magnetic flux, to the published ones for a piezoelectric body of revolution because no results have been published for an MEE body of revolution. The developed solutions are further employed to examine the effects of the direction of polarization, the configuration of the body of revolution and the material components on the orders of the singularities in bodies of revolution that comprise a single MEE material (BaTiO3-CoFe2O4) and bonded MEE/isotropic elastic (BaTiO3-CoFe2O4/Si), MEE/piezoelectric (BaTiO3-CoFe2O4/PZT-5H), or MEE/MEE (BaTiO3-CoFe2O4 (V-I = 50%)/BaTiO3-CoFe2O4(V-I = 20%)) materials. These results are published here for the first time. (C) 2012 Elsevier Ltd. All rights reserved.
Stress singularities in an anisotropic body of revolution
(2014-05-15)
Huang, C. S.
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Hu, C. N.
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Lee, C. C.
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Chang, M. J.
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土木工程學系
To fill the gap in the literature on the application of three-dimensional elasticity theory to geometrically induced stress singularities, this work develops asymptotic solutions for Williams-type stress singularities in bodies of revolution that are made of rectilinearly anisotropic materials. The Cartesian coordinate system used to describe the material properties differs from the coordinate system used to describe the geometry of a body of revolution, so the problems under consideration are very complicated. The eigenfunction expansion approach is combined with a power series solution technique to find the asymptotic solutions by directly solving the three-dimensional equilibrium equations in terms of the displacement components. The correctness of the proposed solution is verified by convergence studies and by comparisons with results obtained using closed-form characteristic equations for an isotropic body of revolution and using the commercial finite element program ABAQUS for orthotropic bodies of revolution. Thereafter, the solution is employed to comprehensively examine the singularities of bodies of revolution with different geometries, made of a single material or bi-materials, under different boundary conditions. (C) 2014 Elsevier Ltd. All rights reserved.
Three-dimensional analyses of stress singularities at the vertex of a piezoelectric wedge
(2013-03-15)
Huang, C. S.
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Hu, C. N.
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土木工程學系
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Department of Civil Engineering
The electroelastic singularities at the vertex of a rectilinearly polarized piezoelectric wedge are investigated using three-dimensional piezoelasticity theory. An eigenfunction expansion approach is combined with a power series solution technique to find the asymptotic solutions at the vertex of the wedge by directly solving the three-dimensional equilibrium and Maxwell's equations in terms of the displacement components and electric potential. This study is the first to address the problems in which the polarization direction of the piezoelectric material is not necessarily either parallel to the normal of the mid-plane of wedge or in the mid-plane. The correctness of the proposed solution is verified by convergence studies and comparison with the published results that are based on generalized plan strain assumption. The solution is further employed to study comprehensively the effect of the direction of polarization on the electroelastic singularities of wedges that contain a single material (PZT-5H), bounded piezo/isotropic elastic materials (PZT-5H/Si), or piezo/piezo materials (PZT-5H/PZT-4). (C) 2012 Elsevier Inc. All rights reserved.