6926475971

Lockheed Missiles & Space Co.. Inc., Sunnyyałe, CA. J. Spacecraft Rockets, 21 (1), pp 6-8 (Jan/Feb 1984) 4 figs, 2 refs

Kay Word*: Beam*. Flutter

A technique i* presented for rapid construction of approxi* mata fluttar boundaries for a baam without acces* to detailed ttructural informatlon. The method i* a utaful preliminary detign tool which permit* aasy evaluatbn of the effects of design change* thereby facllitating finding the maant to aiiminata eeroelastic instability, should H occur. An exampJe i* praaantad from a recent analytis of tha dynamie aeroelastic ftabiiity of *>ece shuttla protuberance*.

84-1707

lmproved Finhe-Difference Analysis of Uncoupled Yibrations of Tapfred Cantilewr Beaini

K.B. Subrahmanyam and K.R.V. Kaza NASA Lewis Res. Ctr., Cleveland, OH. Rept. No. E-1828, NASA-TM-83495, 39 pp (Sept 1983) N84-13610

Kay Word*: Baam*. Cantilavar baam*, Variabla cross saction, Natura/ frequencies. Modę shapes

An itnproved finita drfference procedura for determining tha natura) fraquancias and moda shapas of tapered cantiiavar baams undargoing uncoupled vibratton» is praaantad. Bound-ary conditions ara darłvad in tha form of simple recursiva rełations involving tha eecond order central dWerencet. Ra-sults obtainad by using tha conventional first order central differences and tha present tecond order central diffarancas ara comparad. and ft is obsaryad that tha prasant sacond order acham# i* mora efficient than tha convantk>nal ap-proach.

84-1708

Cosi pled Tbermoełastie Yibration* of a Timodsenko Beam

C.V. Massalasand V.K. Kalpakidis Dept. of Mechanics, Univ. of loannina. loannina, Greece, Intl. J. Engrg. Sci.. 22 (4). pp 459-465 (1984) 4 figs, 12 refs

Kay Word*: Baams, Tlmoshenko theory. Temperatura effects

Tha dynamie behevior of a Tlmoshenko baam subjected to a step haat flux to tha surfa ca z - +h/2 at tkną t - 0⁺ is studiad. The mathematical ana/ysis is basad on intagral transforms, tha Muller'* method of aołving algabraic equa-tions and tha Heeviside axpansion thaoram. From tha nu-m er i cal rasults prasamad the effect of inartia and that of tha coupling betwaen temperatura and strain field* on tha dynamie behavk>r of tha beam as wali as the distribution of tha temperatura field* with tima is shown.

84-1709

Acouatic Radiation from a Yiacoełastic Beam Im-pacted by a Steel Spbere

M. Sakata, M. Horii, and T. Kimura Tokyo Inst. of Tech., Meguro-ku. Tokyo 152, Japan. J. Sound Vib.,_92_ (1), pp 67-81 (Jan 8. 1984) 12 figs, 3 tables, 12 refs

Kay Word*: Baams, Viscoelastic properties. Impact reiponse, Flaxural yibration

Tha aooustic radiation from a viscoelastic baam impact ad by a staal sphere is studiad theoretically and axparimantally. Transy ar sa yibration* of free-free yisooelastic baam* ara analyzed by amploying tha modal analysis tachniqua and an approKlmate method. włth the Hertz theory usad to evaluate impact forcas. Tha wave aquatk>n was solvad to determine tha a co u stic pras*ure radietad from impact ad baams of circular and alliptical cross-sactions. Tha theoretical predic-tions ara comparad with the experimental rasults for tha radiation from PMMA baams of circular and ractangular cross-sactions.

84-1710

Yibration Reaponse of Geometricalły Nonlinear Elastic Beams to Pulie and Impact Loading

H. Liebowitz

School of Engrg. and Applied Science, George Washington Univ„ Washington, DC. Rept. No. NASA-CR-174495. 33 pp (Oct 7. 1983)

N84-12527

Kay Wrods: Baams, Pulsa axcitation, Impact axcitation, Vibration re«>onse

Tha govarning equetk>ns for tha geometricalły nonlinear deformetion of a la Stic baams subjected to dynamie bending loads ara davalopad and solved for various initial conditions. Of prlmary intarast Is tha response to pulsa loading and simuteted impact. Both transiant and savaral cycla Solutions ara ganaratad for tha free yibration response to pulsa loading. Tha rasults obtainad ara comparad to a first moda

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