Thesis-1991-Shellabear.pdf (5.74 MB)
Application of electronic speckle pattern interferometry to the study of three-dimensional mechanical vibrations
thesis
posted on 2012-10-02, 13:30 authored by Michael C. ShellabearElectronic speckle pattern interferometry (ESPI) has become an established
technique for mechanical vibration analysis, but in the past has been restricted to
uniaxial measurements and has suffered from producing results which require
skilled interpretation. The work reported here has extended the range of
application of the technique to include three-dimensional vibration studies, and has
made progress in automating the acquisition and processing of data. After
establishing the importance of empirical vibration analysis and the practical
advantages of ESPI, the theoretical requirements for measuring three-dimensional
motion are considered. An experimental rig has been constructed using a
continuous wave laser which has demonstrated that ESPI is capable of measuring
time-averaged in-plane vibrations, an ability which was previously in some doubt.
The rig has been used to study the three-dimensional resonant behaviour of simple
structures and real engineering components in laboratory conditions. Some
limitations were encountered and, in order to overcome these, a pulsed laser was
introduced to the system. This has enabled the method to be extended to unstable
objects, large amplitudes and non-resonant behaviour. Image processing and
phase-stepping techniques have also been applied, enabling quantitative in-plane
and out-of-plane displacement plots to be computed from the ESPI data.
Experimental results are presented showing modal analyses of flat plates, an
ultrasonic forming die, a turbocharger blade and an ultrasonic cutting system. The
application of pulsed ESPI to the study of travelling waves, unstable objects and
factory environment measurements is also demonstrated. The performance of
three-dimensional ESPI is compared with alternative techniques, and the potential
for further improving the technique is discussed. It is concluded that the method
offers particular advantages for some types of study, and that it compliments the
existing range of empirical techniques.
History
School
- Mechanical, Electrical and Manufacturing Engineering
Publisher
© M.C. ShellabearPublication date
1991Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Language
- en