A thin adhesive film, located between two bonded adherents, is capable of localizing the energy of elastic waves in the form of an interface wave. Under study are the phase velocity and transmission losses of the interface wave which were measured during the entire course of polymerization of the adhesive. It is shown that the phase velocity of the interface wave and the effective shear modulus of the interface film, calculated from the velocity data, are related to the strength of the adhesive bonds. The general transmission loss factor, which is a function of the relaxation maximum of losses arising during the course of polymerization of the adhesive, is another parameter correlated with the strength. The shear strength of the joint was determined on a special specimen in the form of a lap joint, which was also used for acoustic measurements.

Temperature gradients that develop in ceramic materials during microwave heating are known to be strongly dependent on the applied microwave frequency. To gain a better understanding of this dependence, identical samples of ZnO powder compacts were microwave heated at three distinct widely separated frequencies of 2.45, 30, and 83 GHz and the core and surface temperatures were simultaneously monitored. At 2.45 GHz, the approximately uniform “volumetric” heating tends to raise the temperature of the sample as a whole, but the interior becomes hotter than the exterior because of heat loss from the surface. At 30 and 83 GHz, this interior to exterior temperature difference was found to be reversed, especially for high heating rates. This reversal resulted from increased energy deposition close to the sample's surface associated with reduced skin depth. A model for solving Maxwell's equations was incorporated into a newly developed two‐dimensional (2‐D) heat transport simulation code. The numerical simulations are in agreement with the experimental results. Simultaneous application of two or more widely separated frequencies is expected to allow electronic tailoring of the temperature profile during sintering.

Ultrasonically determined elastic moduli in ZnO samples sintered to various densities were evaluated using both an empirical model and the Mori‐Tanaka effective field theory. Both approaches have been successfully used to model the modulus‐porosity relations in several material systems. In the present investigation, application of the empirical model predicted elastic moduli which deviated significantly from the experimental results. The deviation was attributed to the porosity dependence of Poisson's ratio which was neglected in this model. When this dependence was accounted for empirically, the fit to the experimental data was improved dramatically. Analysis of the data in the context of the Mori‐Tanaka model indicates that the porosity shape changes significantly during the sintering process. This analysis may provide a convenient way to quantitatively compare such changes for ceramic materials prepared by different processing techniques, such as by conventional and microwave sintering.

The waveguide properties of a thin film separating two elastic half-spaces possessing a shear modulus higher than the shear modulus of the film are investigated. It is shown analytically and experimentally that such a film is capable of localizing the energy of elastic waves near the interface. The velocity of the interface wave is determined by shear modulus, density, thickness of the film, and by the elastic properties of the substrates. The velocity of the interface wave lies between that of the Rayleigh and that of the shear waves in the solid half-spaces. It is shown that the interface wave can be used to estimate the elastic and dissipation properties of thin interface layers.

Patients with severe action tremor have uncontrollable, relatively rapid oscillatory motion super-imposed on otherwise useable slower voluntary motor activity. Because a mechanical damper produces an opposing force proportional to velocity, applying damping loads to tremorous limbs should attenuate the (high-velocity) tremor component of movement while permitting the slower purposeful portion to proceed relatively unopposed. In this study, the effect of upper extremity damping in three degrees of freedom was examined in 10 patients with cerebellar action tremor due to multiple sclerosis or traumatic brain injury. Variable amounts of damping were applied by prototype energy-dissipating orthoses which generated resistive viscous loads by means of computer-controlled magnetic particle brakes. All patients experienced statistically and functionally significant tremor reduction with the application of damping.

The effect of porosity on the complex dielectric permittivity of microwave sintered zinc oxide at room temperature and 2.45 GHz is reported. The predictions of conventional Maxwell–Garnet theory and the effective medium approximation are in poor agreement with the experimental results. Various methods are employed to investigate the system in an effort to come up with new mixing laws, including combinations of these two analytic theories and finite difference electromagnetic simulations of representative microstructures. A model that assumes the existence of dielectrically inactive, fractal-geometry boundaries between ceramic grains provides an excellent description of the results with no free parameters. It gives physical insight into the experimentally observed mixing law.

The longitudinal and transverse acoustic velocities and the ultrasonic attenuations in high-purity polycrystalline gadolinium, terbium, dysprosium, holmium, and erbium metals have been measured by a pulse technique at a frequency of 10 MHz between 4.2 and 300°K. The variations with temperature of the Young moduli JE, shear moduli G, adiabatic compressibilities K s , and Debye temperatures QD have been determined. The anomalies observed in the elastic and anelastic behavior were correlated with the magnetic transitions known to occur in these metals. The behavior of the elastic properties and ultrasonic attenuations in the vicinity of the majority of the magnetic transition points was in accord with the criteria of Landau et al.'s theories of second-order phase changes. Exceptions are the ferromagnetic transitions in terbium and dysprosium, and the change in the antiferromagnetic structure of erbium at 56°K. The character of the elasticity anomalies in these three cases tends to indicate that they are of first order. The abrupt change in the easy direction of magnetization in gadolinium at 224°K is sharply manifested in the elastic and anelastic properties. Determination of these properties in holmium revealed an anomalous behavior at 70°K. The temperature variation of the Debye temperatures in gadolinium, terbium, dysprosium, holmium, and erbium depicts the elasticity behavior. The limiting Debye temperatures at 0°K are, in general, higher than those obtained from specific-heat measurements.

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