Non-uniform Material Properties Research Articles

Distortionless piezoelectric transducers with nonuniform electroelastic parameters

Of concern are the generation and detection of sound by piezoelectric transducers with nonuniform material properties along the principal axis. It is shown that subject to conditions of distortionless propagation [V. Burke, R. J. Duffin, and D. Hazony, “Distortionless Wave Propagation in Inhomogeneous Media and Transmission Lines,” Q. Appl. Math. 183–194 (July 1976)] it is possible to associate a circuit model with the transducer similar to the Mason model [W. P. Mason, Electromechanical Transducers and Wave Filters (Van Nostrand, New York, 1948)]. This work follows the development of spherical shell piezoelectric transducers [D. Hazony, “Nonuniformly Poled Spherical Shell Piezoelectric Transducers,” J. Acoust. Soc. Am. 81, 1624–1627 (1987)]. [Work supported in part by Tecsonics, Inc.]

Three-dimensional large displacement analysis of orthodontic appliances

An incremental technique for predicting the nonlinear load-displacement characteristics of orthodontic appliances is developed. The analysis is based upon a three-dimensional finite-difference formulation which permits the treatment of appliances that have arbitrary configurations and non-uniform material and cross-sectional properties. The effects of intermediate loading and attached springs may also be studied. The results show the activated configurations and the associated force-couple systems for three appliances that are activated to the yield point. The incremental analysis results are compared to those of the linear solution for each case.

Local and Overall Buckling of Cold-Formed Members

The combined effects of local buckling, overall column buckling, and nonuniform material properties in compression members are studied. The results are given for 34 tests on two types of columns, one with local buckling occurring in elements supported along both longitudinal edges, and one with local buckling occurring in elements along only one longitudinal edge. Based on these tests, an analytical approach is presented for predicting the ultimate strength of columns subject to the factors just mentioned. Column buckling is accounted for by means of the tangent modulus concept and post-buckling behavior of plate elements by utilizing the effective width expression developed by the third writer. A simpler approximation of the analytical approach is also given for routine design.

Performance of Foil Supported Electrode System and Plans for Improvement

In a previous communication the advantages and the performance of foil supported wires for counter arrays were described, and we hinted at rate limitations caused by voltage drop in the resistive foil. The non-uniform material properties which are never quite ruled out initially and often develop under irradiation, particle bombardment etc. - at least on the surface of organic foils, and the recent increase of stable gas-amplification make these limitations severe beyond our first expectation. This is a preliminary report on a changed approach: we use a good insulator for supporting the foil and eliminate the field distortion caused by surface charges through a self shielding geometry described below.

Thermo-elastic-plastic stress distribution in composite media with nonuniform temperature distribution and temperature dependent material properties

A formulation and a method of solution are outlined for the thermo-elastic-plastic stress and strain distribution in composite media with nonuniform temperature distribution and temperature dependent material properties. A sample problem demonstrates the practicality of the method. Some results are plotted for a seed plate section of a pressurized water reactor for illustrative purposes.