Accession Number : ADA186139

Title :   Natural Frequencies and Structural Integrity Assessment of Large Space Structures.

Descriptive Note : Technical rept. 1 Sep 85-1 Apr 87,

Corporate Author : WEA CAMBRIDGE MA

Personal Author(s) : Williams, James H , Jr ; Nagem, Raymond J

PDF Url : ADA186139

Report Date : 01 Apr 1987

Pagination or Media Count : 39

Abstract : In a previous report, transfer matrices and joint coupling matrices are used to compute natural frequencies of vibration of a five-bay planar lattice structure. In this report, the problem of detecting damage in the five-bay planar lattice structure is considered. Seven different states of damage are assumed. Each damage state corresponds to a disconnected or partially disconnected joint in the lattice. Transfer matrices and joint coupling matrices are used to compute natural frequencies associated with each damage state. The natural frequencies computed for each damage state are significantly different from the natural frequencies of the undamaged lattice; for example, the frequencies of the first flexible mode of the damaged lattice are 26% to 83% lower than the frequency of the first flexible node of the undamaged lattice. The results presented here demonstrate that measurement of natural frequencies is a potentially useful method for detecting damage in lattice structures, at least, for the types of damage considered here. However, it is also shown here that measurement of natural frequencies alone is not sufficient, in general, to determine the location of damage within the lattice structure. Thus, measurement of natural frequencies should be regarded as only a part of a complete nondestructive evaluation method. After the results obtained here are presented, some suggestions for NDE methods which may be capable of providing more quantitative measures of structural integrity are given.

Descriptors :   *SPACE STATIONS, *STRUCTURAL RESPONSE, *SPACECRAFT COMPONENTS, DAMAGE, MATRICES(MATHEMATICS), MEASUREMENT, NODES, NONDESTRUCTIVE TESTING, RELIABILITY, RESONANT FREQUENCY, SPACECRAFT, STRUCTURAL PROPERTIES, TRANSFER FUNCTIONS, VIBRATION

Subject Categories : Mechanics
      Unmanned Spacecraft

Distribution Statement : APPROVED FOR PUBLIC RELEASE