Accession Number : AD0481013

Title :   TORSIONAL OSCILLATIONS OF AN ENCASED HOLLOW CYLINDER OF FINITE LENGTH.

Descriptive Note : Technical rept.,

Corporate Author : NORTHWESTERN UNIV EVANSTON IL STRUCTURAL MECHANICS LAB

Personal Author(s) : Achenbach, Jan D.

Report Date : FEB 1966

Pagination or Media Count : 17

Abstract : A hollow elastic or viscoelastic cylinder of finite length is encased in a thin elastic shell. The analysis of free torsional vibrations of the elastic system yields a transcendental frequency equation that is solved numerically. The modes of free torsional motion are discussed and the proper relation establishing orthogonality of the principal modes is determined. The elementary mode of a free circular cylinder, when each transverse section rotates as a whole, does not occur for an encased cylinder. The exact frequencies are compared with estimates based on the assumption that the material of the core is very compliant as compared to the material of the shell. The regions are discussed in which these estimates are acceptable. Fourier-Bessel analysis is used for the problem of forced torsional motion of the encased elastic core, for arbitrary dependence on radial coordinate and time of the prescribed displacements or stresses at the end-sections. For time-harmonic forcing functions the analysis is extended to forced torsional motion of an encased viscoelastic cylinder. The viscoelastic solutions are derived in terms of the complex shear modulus. The analysis of this paper is of interest for applications in solid-rocket technology. (Author)

Descriptors :   *CYLINDRICAL BODIES), (*VISCOELASTICITY, (*PROPELLANTS, VISCOELASTICITY), ELASTIC SHELLS, MATHEMATICAL ANALYSIS, FOURIER ANALYSIS, BESSEL FUNCTIONS, SHELLS(STRUCTURAL FORMS), STRUCTURAL PROPERTIES, TORSION, VIBRATION, TRANSCENDENTAL FUNCTIONS, POLYNOMIALS, HARMONIC ANALYSIS, SHEAR STRESSES, OSCILLATION.

Subject Categories : Ammunition and Explosives
      Mechanics
      Solid Rocket Propellants

Distribution Statement : APPROVED FOR PUBLIC RELEASE