DYNAMIC STIFFNESS BOUNDARY CONDITIONS DERIVED FROM A FINITE ELEMENT MODEL OF SURROUNDING STRUCTURE BASED ON COMPONENT MODE SYNTHESIS

Authors
  1. Stredulinsky, D.C.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN)
Abstract
This technical memorandum describes the second phase in the development of a method to determine the dynamic stiffness boundary conditions to simulate the influence of the surrounding structure on the frequency response of an extracted structure subjected to harmonic loading. A procedure initially proposed was demonstrated to work well for small finite element models but it was discovered that a complete set of fixed interface modes for the surrounding structure finite element model had to be used to obtain the proper extracted structure response even at low frequencies. A new method has been developed based on a fixed interface component mode synthesis (CMS) technique. This new method was first tested for a discrete multiple mass/spring system using equations implemented symbolically in Maple V. Analytical expressions for the dynamic boundary stiffness matrix were obtained as a function of forcing frequency for the system, using both the origin method and the new method. Based on the promising outcome of the Maple implementation, the new procedure was implemented in conjunction with the VAST finite element code. The surrounding structure was considered as a VAST super element with master nodes on the interface to the extracted structure. The VAST CMS module was used to generate reduced stiffness and mass matrices for the surrounding structure. TRUNCATED
Keywords
BOUNDARY CONDITIONS;BOUNDARY STIFFNESS;COMPONENT MODE SYNTHESIS;DYNAMIC STIFFNESS
Report Number
DREA-TM-94-204 — Technical Memorandum
Date of publication
01 Mar 1994
Number of Pages
55
DSTKIM No
94-03440
CANDIS No
141019
Format(s):
Hardcopy;Originator's fiche received by DSIS

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