Kennedy Method Research Articles

The Determination of Modal Shapes in Resonance Testing

An experimental study is described which shows the elementary ‘peak-amplitude’ technique of resonance testing to great disadvantage. On the basis of that method the experimentally determined ‘modal shapes’ are completely misleading. While the Kennedy and Pancu method would produce acceptable modes it would demand a much greater effort. An alternative technique is described which gives excellent results at the cost of much less labour. While the new method appears to have an added advantage over the Kennedy and Pancu method when there is strong coupling between the modes, it may well prove to be less accurate when there are close natural frequencies.

A Critical Introduction to Some Industrial Resonance Testing Techniques

This paper gives details of apparatus which was designed to permit an initial appraisal to be made of methods of resonance testing. A fairly lightly damped system with widely spaced natural frequencies was used. The ‘peak-amplitude’ technique of testing gave excellent and consistent results, though a simple alternative (and apparently novel) approach was superior in one respect, namely for the measurement of resonant frequencies. The Kennedy and Pancu method also gave good results but required more effort. A recently-suggested method of estimating damping was not found to be satisfactory or as good as the standard methods for the uncomplicated system under test. The simplest dynamical systems, then, appear to demand only the simplest of the techniques in current use in industry.