Masters Theses


"This thesis presents the results of the research investigation on damage detection in mechanical and civil structures using Laser Vibrometer and ultrasonic imaging techniques. The effect of pulse-repetition-rate frequency on the detection of fabricated damage in composite and aluminum plates is investigated. It was observed that intermediate pulse-rate frequencies worked best for testing of composites and low pulse frequencies worked best for the testing of aluminum. Different sizes and depths of defects are tested using the ultrasonic C-Scan imaging technique. A radial basis function neural network was trained using the experimental results and used to predict the actual size and depth of the defects. The C-Scan imaging technique was also used to test for damage in fabricated concrete slabs. The results show the fabricated rectangular defects in concrete along with the inherent porosity arising during fabrication in both the undamaged and damaged concrete slabs. To separate the material irregularities from the major defects that would affect the life and integrity of concrete slabs, three statistical and one wavelet filtering technique were applied to the scan data. The results clearly showed the presence and location of the rectangular voids. It was observed that median filtering worked better than mean filtering, gaussian filtering and wavelet filtering. Modal analysis with wavelet transforms was also investigated for the purpose of detecting the presence, location and extent of defects in aluminum beams. Finite element analysis and the Laser Vibrometer were used to determine the mode shapes of different modes of vibration of an aluminum beam and the results used to construct a first-order regression model for predicting the severity of damage from the wavelet coefficient"--Abstract, page iv.


Okafor, A. Chukwujekwu (Anthony Chukwujekwu)

Committee Member(s)

Koval, Leslie Robert
Rao, Vittal S.


Mechanical and Aerospace Engineering

Degree Name

M.S. in Mechanical Engineering


University of Missouri--Rolla

Publication Date

Summer 2000

Journal article titles appearing in thesis/dissertation

  • Non destructive evaluation of concrete with ultrasonic C-Scan and digital image enhancement techniques
  • Determination of optimal ultrasonic pulse repetition rate frequency for damage detection in composites and aluminum plates using neural networks
  • Structural damage detection in beams by wavelet transforms


xi, 97 pages

Note about bibliography

Includes bibliographical references.


© 2000 Amitabha Dutta, All rights reserved.

Document Type

Thesis - Restricted Access

File Type




Thesis Number

T 7823

Print OCLC #


Link to Catalog Record

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