The Determination of Modal Shapes in Resonance Testing

Abstract

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.