Arc plasma fabricated phase shifter elements
It has been established that the arc plasma process can be used to fabricate ferrite phasors. The resultant ferrite-dielectric composite, except for the coercive force, has excellent microwave device characteristics. With the advent of a dielectric possessing optimum temperature coefficient of expansion, a phasor can be arc plasma sprayed which will be economical and exhibit the required device performance for phased arrays. The greatest economic impact of the arc plasma is expected to be in phasors requiring thin ferrite walls, since these are more difficult to fabricate by current processes and can be arc plasma fabricated at rapid rates. It should be noted that to achieve low cost phasors with the arc plasma technique, massive production numbers of phasors (in excess of 100,000 units) (6), are not required. That is, one can arc plasma fabricate a relatively small number of phasors and still maintain the economics of this technique.
Arc Plasma Deposition of Nickel Zinc Ferrites
Abstract : Nickel zinc ferrite powders prepared by flame spraying, fluid bed reactions, and a conventional spray dried technique were deposited on ceramic substrates by arc plasma spraying. The deposition rate was dependent upon the powder preparation technique. The magnetic properties evaluated were temperature coefficient, the real part of the permeability tensor, coercive force, and squareness ratio. It was noted that the squareness ratio of arc plasma deposited ferrite was substantially higher than for the same composition conventionally densified. The arc current and the distance from the arc plasma gun to the substrate influenced the values of temperature coefficient, permeability tensor, and coercive force. Measurements of saturation magnetization and resistivity of the deposited ferrite were also made, and the reproducibility of the arc plasma was evaluated. Possible mechanisms for some of the observed phenomena are discussed.
Evaluation of buckling load and dynamic performance of steel shear wall retrofitted with strips made of shape memory alloy
One of the most imperfections of the steel shear wall is out of plane displacements that cause severe damage in both structural and non-structural elements. In this paper, the effects of shape-memory alloys on steel shear walls are investigated. First, a numerical analysis using the finite element method in ABAQUS software has been carried out according to an experimental test. The results of the numerical analysis have been verified with experimental results. Next, shape-memory alloy fibers have been added vertically and horizontally to various parts of the steel shear wall. The results show that retrofitting with the shape-memory alloy reduces the out-of-plane displacement of the steel shear wall under both cyclic and seismic loadings. Besides, the buckling load in the steel shear wall increases when it is retrofitted with the shape-memory alloy. Also, the total out-of-plane movement (accumulated absolute displacements) of the steel shear wall and non-structural damage are controlled by the characteristic of a shape-memory alloy material called “super-elastic”.