Vol.5, No 1, 2007pp. 1 - 9
UDC 621.825.2 : 531.65
MODIFICATION OF THE DYNAMICS CHARACTERISTICS
IN THE STRUCTURAL DYNAMIC REANALYSIS
Nataša Trišović
Faculty of Mechanical Engineering,
University of Belgrade, Kraljice Marije 16, 11000 Belgrade
E-mail: ntrisovic@mas.bg.ac.yu
Abstract. Structural dynamic modification (SDM) techniques can be
defined as methods by which the dynamic behavior of a structure is improved
by predicting the modified behavior brought about by adding modifications
like those of lumped masses, rigid links, dampers, beams, etc. or by variations
in the configuration parameters of the structure itself. Such methods,
especially those with their roots in finite element models, have often
been described as reanalysis. Most of the techniques imply a dynamic test
at some stage of SDM and currently prefer implementation on a personal
computer. The need for SDM arises because of the demands on higher performance
capabilities of complex mechanical and structural systems, like machine
tools, automobiles, rail vehicles, aerospace systems and high speed rotating
systems, which require sound dynamic design, i.e. desired dynamic characteristics
like vibration levels, response, resonances, eigenvalues, dynamic stability
and mode shapes. Structural dynamic modification implies the incorporation,
into an existing model, of new information gained either from experimental
testing or some other source, which questions or improves the accuracy
of the model. This paper deals with improving of dynamic characteristics
of tube collector (protection pipe of conductors of transformer) of the
ring cross section. It is shown how change of conditions of support can
improve dynamic characteristics of structure. Distribution of potential
and kinetic energy in every finite element is used for analysis. In this
study it is shown that structural dynamic modification is important in
structural reanalysis.
Key Words: Structural Dynamics Modification, Eigenvalues, Potential
and Kinetic Energy.
MODIFIKACIJA DINAMIČKIH KARAKTERISTIKA
U STRUKTURALNOJ REANALIZI MEHANIČKIH SISTEMA
Tehnika strukturne dinamičke modifikacije (SDM) može se definisati kao
skup metoda pomoću kojih se dinamičko ponašanje konstrukcije može popraviti
procenom modifikovanog ponašanja dobijenog dodavanjem modifikacija kao
na primer koncentrisanih masa, krutih veza, prigušenja, novih elemenata,
isl. ili promenom konfiguracionih parametara u samoj strukturi. Takve metode
kod kojih je osnov metod konačnih elemenata se često se nazivaju metode
reanalize. Potreba za strukturnom dinamičkom modifikacijom se pojavila
zbog zahteva za višim performansama složenih mašina i strukturnih sistema,
kao što su mašine alatke, automobili, šinska vozila, avioni, i sistemi
sa velikim brojem obrtaja, koji zahtevaju zvučno dinamičko projektovanje,
odnosno željene dinamičke karakteristike kao što su nivo vibracija/odziv,
rezonanca/sopstvene vrednosti, dinamička stabilnost i modalni oblici.
Ovaj rad se bavi poboljšanjem dinamičkih karakteristika jedne cevne sabirnice
prstenastog poprečnog preseka. Pokazano je kako se promenom graničnih
uslova i geometrije mogu popraviti dinamičke karakteristike konstrukcije.
U toj analizi se koristi raspodela potencijalne i kinetičke energije u
svakom konačnom elementu. Takođje, pokazano je da dinamička modifikacija
igra važnu ulogu u reanalizi konstrukcija.
Ključne reči: dinamička modifikacija konstrukcija, sopstvene
vrednosti, potencijalna i kinetička energija
