Abstract

The objective of this study was to perform analyses for the static and dynamic mechanical response of a 36 ft fiberglass whip antenna for the purpose of determining survivability under nuclear weapons effects. The static analysis was to obtain the stiffness/deflection characteristics of the antenna using material, wall-thickness, and mechanical loading history provided by the Naval Surface Warfare Center. The results of the static analysis were then to be used in a NASTRAN transient dynamic analysis. The effect of the thermal pulse associated with the blast was not directly considered in these studies.

An analytical model of the whip antenna deflected by transverse loading was developed using Castigliano’s Theorem. The resulting integrals were evaluated using Mathematica™. The diameters, wall thicknesses, and mass density resulting from the static response study were then used in the linear, transient dynamic analysis.

These studies concluded that the suggested modeling approach is suitable for the static and linear transient dynamic response analysis of a standard 36 foot fiberglass whip antenna to a 4 KT, 7 psi air blast (without thermal effects). The “Basic” model suggests a linear finite element model maximum deformation to be within 10% of the deflection of about 16 feet observed in the test video. Low-to-midrange stresses are expected at this deformation. A 1 MT, 7 psi air blast would probably, but not necessarily, fail the antenna. These studies support the conclusion that the dynamic response of a standard 36 ft whip antenna is “duration-dependent” within the range of overpressures considered.

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