Discrete-Layer Piezoelectric Plate and Shell Models for Active Tip-Clearance Control

The objectives of this work were to develop computational tools for the analysis of active-sensory composite structures with added or embedded piezoelectric layers. The targeted application for this class of smart composite laminates and the analytical development is the accomplishment of active tip-clearance control in turbomachinery components. Two distinct theories and analytical models were developed and explored under this contract: (1) a discrete-layer plate theory and corresponding computational models, and (2) a three dimensional general discrete-layer element generated in curvilinear coordinates for modeling laminated composite piezoelectric shells. Both models were developed from the complete electromechanical constitutive relations of piezoelectric materials, and incorporate both displacements and potentials as state variables. This report describes the development and results of these models. The discrete-layer theories imply that the displacement field and electrostatic potential through-the-thickness of the laminate are described over an individual layer rather than as a smeared function over the thickness of the entire plate or shell thickness. This is especially crucial for composites with embedded piezoelectric layers, as the actuating and sensing elements within these layers are poorly represented by effective or smeared properties. Linear Lagrange interpolation polynomials were used to describe the through-thickness laminate behavior. Both analytic and finite element approximations were used in the plane or surface of the structure. In this context, theoretical developments are presented for the discrete-layer plate theory, the discrete-layer shell theory, and the formulation of an exact solution for simply-supported piezoelectric plates. Finally, evaluations and results from a number of separate examples are presented for the static and dynamic analysis of the plate geometry. Comparisons between the different approaches are provided when possible, and initial conclusions regarding the accuracy and limitations of these models are given

Capactitive probe array measurements and limitations

This paper reviews the use of electrostatic capacitive probes for detections and evaluations of dielectric material properties and flaws. Interest in using both inductive and capacitive arrays for proximity sensing, surface feature characterization, material properties evaluation, and flaw detecting has increased steadily since the mid-1980’s [1–7]. Two other papers [6,7] in this proceedings also discuss the present state of the art, particularly with regard to the measurement of lossy dielectrics (complex permittivity). In traditional dielectrometry measurements (as well as in eddy-current measurements of material properties evaluation) varying the probe frequency has long been used as a tool for extracting information about dispersion and loss mechanisms. Use of a spatially periodic array probe interrogates the material, or flaw, with a field that penetrates into the sample to a degree determined by the periodicity. This controllable penetration phenomenon (artificial-skin effect or zoom effect) has been successfully exploited by Melcher, Zaretsky [5], and Goldfine [6] in what they call imposed w-k magnetometry and dielectrometry, using interdigital probes of different periodicities. Details are given in these proceedings. Gammell’s paper [7] gives a progress report on complex permittivity measurements using probes of more conventional type

Understanding the potential in vitro modes of action of bis(β‐diketonato) oxovanadium(IV) complexes

To understand the potential in vitro modes of action of bis(β-diketonato) oxovanadium(IV) complexes, nine compounds of varying functionality have been screened using a range of biological techniques. The antiproliferative activity against a range of cancerous and normal cell lines has been determined, and show these complexes are particularly sensitive against the lung carcinoma cell line, A549. Annexin V (apoptosis) and Caspase-3/7 assays were studied to confirm these complexes induce programmed cell death. While gel electrophoresis was used to determine DNA cleavage activity and production of reactive oxygen species (ROS), the Comet assay was used to determine induced genomic DNA damage. Additionally, Förster resonance energy transfer (FRET)-based DNA melting and fluorescent intercalation displacement assays have been used to determine the interaction of the complexes with double strand (DS) DNA and to establish preferential DNA base-pair binding (AT versus GC)

Finite Element Model of Stress Wave Topology in Unidirectional Graphite/Epoxy: Wave Velocities and Flux Deviations

Until recently, the use of a finite element model (FEM) to simulate stress wave propagation has been limited to solutions where the number of degrees of freedom are kept to a minimum, because of hardware limitations on computer memory and computational speed. With the advent of a number of new supercomputers, numerical simulation becomes a reasonable approach to some simpler problems. Recently, Ludwig, et. at [1,2] have demonstrated the feasibility of such an approach for problems where materials are either isotropic or only slightly anisotropic. We extend this effort to unidirectional graphite/epoxy which has large variations in elastic properties. For this material the effect of elastic anisotropy on stress wave propagation has been studied both experimentally and analytically [3,4] and several interesting properties have been predicted and measured: mode transitions, sensitivity of flux deviations to small changes in anisotropy, and shear wave speeds exceeding longitudinal waves. With a FEM we can simulate and study some of these properties most effectively.</p

Static Deformation of a Spherically Anisotropic and Multilayered Magneto-Electro-Elastic Hollow Sphere

In this paper, we present an analytical solution on the general static deformation of a spherically anisotropic and multilayered magneto-electro-elastic (MEE) hollow sphere. We first express the general solution in each layer in terms of the spherical system of vector functions where two transformations of variables are also proposed to achieve the analytical results. The spherical system of vector functions can be applied to expand any vector as well as scalar function, and it further automatically separates the static deformation into two independent sub-problems: The LM-type and N-type. The LM-type is associated with the spheroidal deformation and is coupled further with the electric and magnetic fields. The N-type is associated with the torsional deformation and is purely elastic and independent of the electric and magnetic fields. To solve the multilayered spherical problem, the propagation matrix method is introduced with the propagation matrix being simply the exponential matrix for each layer. By assuming the continuity conditions on the interface between the adjacent spherical shells, the solution can be simply propagated from the inner surface to the outer surface of the layered and hollow MEE sphere so that specific boundary value problems can be solved. As numerical examples, a three-layered sandwich hollow sphere with different stacking sequences under different boundary conditions is studied. Our results illustrate the influence of the stacking sequences while showing the effectiveness of the proposed method