Dynamic characteristics and modal parameters of a plate with a surface crack

Chen, Yin (1992) Dynamic characteristics and modal parameters of a plate with a surface crack. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (10MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

A systematic study of the behaviour of a plate with a surface crack is carried out using the finite element method. Static, steady state, resonant and transient responses of the cracked plate are examined. Strain, displacement and acceleration responses without/with the crack are computed. Modal analysis is performed to determine the natural frequencies, mode shapes and strain/displacement frequency response functions. Frequency response functions without/with the crack are computed. Strain mode shapes, as well as displacement mode shapes, are obtained. The difference of the strain mode shapes between the uncracked plate and the cracked plate is calculated. Each of the parameters mentioned above is examined to determine the sensitivity of this parameter to the crack that occurs in the structure. -- By using all the methods of analysis mentioned above, and comparing the sensitivity of different parameters to cracking, it is found that the surface crack in the structure will affect most of the dynamic characteristics such as strain/stress field around the crack, natural frequencies of the structure, amplitudes of the response and mode shapes. Some of the most sensitive parameters are the difference of the strain mode shapes and the local strain frequency response functions. By monitoring the changes in the local strain frequency response functions and difference of strain mode shapes, the location and severity of the crack that occurs in the structure can be determined. Based on these results, suitable procedures for detecting the crack in real structures are suggested.

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