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.
Polycrystalline Ferrite Films for Microwave Applications Deposited by Arc‐Plasma
The arc‐plasma spray deposition has been successfully applied to fabrication of planar ferrite microwave integrated circuits. Powdered commercial sintered microwave ferrites were deposited at rates up to 2 mils/min on 1 sq in. dielectric substrates by arc‐plasma spray deposition. Process controls produced densities >99% theoretical and also maintained stoichiometric agreement between deposited films and starting material. Annealing expanded <0.1 μ grains to useful sizes of 1 to 20 μ and controlled cation distribution. Special annealing techniques were necessary for ferrites having volatile products such as Ni–Zn compounds. Magnetic and microwave properties of several deposited Mg–Mn ferrites and CeYIG agreed closely with bulk values. Remanence ratios up to 0.87 were noted. Practical application of arc‐plasma deposition required material compatibility studies at high temperature. These considerations often superseded microwave properties as criteria for material section.
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.