Steven W. Meeks

Bio: Steven W. Meeks is an academic researcher. The author has contributed to research in topics: Piezoelectricity & Amorphous metal. The author has an hindex of 4, co-authored 6 publications receiving 41 citations.

Effects of static and dynamic stress on the piezoelectric and dielectric properties of PVF2

Abstract: The effects of hydrostatic pressure and pressure cycling on the piezoelectric properties of polyvinylidene fluoride (PVF2) have been experimentally investigated by using an acoustic reciprocity technique. The hydrostatic piezoelectric constants and the relative dielectric constant were measured as a function of pressure and pressure cycling for both voided and nonvoided PVF2 samples. The dynamic response of these materials to high‐amplitude pressure pulses having a rise time of 1–3 ms was also determined. The results showed that the microvoid structures in PVF2 improve the material’s piezoelectric properties but at the same time increase its pressure dependence and introduce a hysteresis effect with changing hydrostatic pressure. Nonvoided PVF2 films were also shown to have a good dynamic response to pressure pulses and, therefore, are promising for applications such as underwater shock sensors.

The evaluation of PVF2 for underwater shock‐wave sensor application

Abstract: A thick‐film polyvinylidene fluoride (PVF2) sample was used to evaluate this material for underwater shock‐sensor applications. The free‐field voltage sensitivity of the sensor showed a flat frequency response with a bandwidth of 2 MHz. The response of the PVF2 sample to a 1‐ms pressure pulse was linear to within 0.6 dB at a peak pressure of 69 MPa. The PVF2 shock sensor also showed reduced high‐frequency ringing in its response to a shock wave when compared with a similar device using a PZT element.

A mobility analogy equivalent circuit of a magnetostrictive transducer in the presence of eddy currents

Abstract: The equivalent circuit in the mobility analogy of a magnetostrictive transducer in the presence of eddy currents is derived. This equivalent circuit is used to predict the effect of eddy currents on the efficiency, the electrical impedance, the transmitting responses, and the receiving sensitivity of a magnetostrictive transducer. Lumped‐parameter equivalent circuits are also presented which use approximations to the exact theory to simply and accurately predict the efficiency and electrical impedance of a transducer with eddy currents within a frequency range of practical interest near the clamped characteristic frequency. It was found that the eddy current theory predicted a sharp drop in the eddy current loss in a narrow frequency range just past resonance. This effect was experimentally observed by Savage and Abbundi [IEEE Trans. Magn. 14, 545 (1978)].

Magnetic boundary conditions for metallic–glass piezomagnetic transducers

Abstract: It has been shown by comparison of theory and experiment that metallic–glass piezomagnetic ribbons can have boundary conditions intermediate to constant B or constant H. It is argued that this intermediate boundary condition is due to partial rotation of the transverse magnetization at very low fields in the 2605SC alloy. An empirical relation for k33 has been derived for metallic–glass alloys with intermediate boundary conditions.

Proposed experimental tests of a theory of fine microstructure and the two-well problem

Abstract: Predictions are made based on an analysis of a new nonlinear theory of martensitic transformations introduced by the authors The crystal is modelled as a nonlinear elastic material, with a free-energy function that is invariant with respect to both rigid-body rotations and the appropriate crystallographic symmetries The predictions concern primarily the two-well problem, that of determining all possible energy-minimizing deformations that can be obtained with two coherent and macroscopically unstressed variants of martensite The set of possible macroscopic deformations obtained is completely determined by the lattice parameters of the material For certain boundary conditions the total free energy does not attain a minimum, and the finer and finer oscillations of minimizing sequences are interpreted as corresponding to microstructure The predictions are amenable to experimental tests The proposed tests involve the comparison of the theoretical predictions with the mechanical response of properly oriented plates subject to simple shear Additional crystallographic background is given for the model, and the theory is compared with the `linearized' model of Khachaturyan, Roitburd and Shatalov There are some similarities in the predictions of the two theories, but also some major discrepancies

Recent Advancements in Bulk Metallic Glasses and Their Applications: A Review

Abstract: Bulk metallic glasses (BMGs), that display extraordinary properties of high strength, corrosion resistance, polymer-like formability, and excellent magnetic properties, are emerging as modern quint...

Biological effects of shock waves: lung hemorrhage by shock waves in dogs--pressure dependence.

Abstract: The most serious side effect observed during the destruction of gallstones by shock waves in dogs was lung bleeding. To determine the conditions leading to lung damage, pressure probes were implanted into dogs between the lung and the diaphragm. The distance between the lung and the focal point of the pressure field was determined at which 1000 shock waves caused no more lung hemorrhage. On the long axis it is greater than 15 cm and perpendicular to the long axis it is 4 cm. Shock wave pressures over 2 MPa could be administered safely, whereas a pressure of 10 MPa caused bleedings in beagles, but probably not in boxers.

Piezoelectricity in crystallizing ferroelectric polymers: Poly(vinylidene fluoride) and its copolymers (A review)

Abstract: The piezoelectricity observed in poly(vinylidene fluoride) (PVDF) and its copolymers involves three components that are associated with the presence of at least two phases (crystalline and amorphous) in the polymer structure. The main contributions to the phenomenon observed are made by the size effect and electrostriction, which are related to each other. These contributions manifest themselves through the mechanism of strain-induced reversible transformations of a number of domains of the anisotropic amorphous phase into the crystalline state under the action of mechanical or electrical fields. With due regard for different packings of chains in the amorphous and crystalline phases, this mechanism accounts for the large Poisson ratios μ31 obtained for textured films of flexible-chain crystallizing polymers. The dependence of the piezoelectric coefficient d 32 on the static stress in textured films is governed by the change in the fraction of the crystalline phase due to strong anisotropy of the elastic constants in the film plane. It is shown that the shear deformations of polymers are characterized by a strong piezoelectric response. The specific features revealed in the piezoelectric effect under bending deformations are described for films with an inhomogeneous distribution of polarization over the cross section. The general regularities of the electrostriction in the polymers and inorganic relaxor ferroelectrics studied are considered.

Characterization of nano-dimensional thin-film elastic moduli using magnetoelastic sensors

Abstract: Application of magnetoelastic thick-film sensors to the measurement of thin-film elastic moduli is described in this study. An analytical model is derived, that relates the resonant frequency of a magnetoelastic sensor to the elasticity and density of an applied thin-film. Limits of the model are analyzed, and related to experimental measurements using thin-films of silver and aluminum. For 500 nm thick-films, the measured Young's modulus of elasticity for Al and Ag is found to be within 1.6% of standard data. Using commercially available magnetoelastic sensors, the elasticity of coatings, approximately 30 nm thick, can readily be measured.