Measuring operational deflection shapes with a scanning P-U probe

Scanning measurement techniques allow reducing significantly the number of sensors required to characterize time-stationary sound fields. Therefore, it is possible to produce sound maps by combining the signal acquired while moving a transducer with its tracking information. Structural vibrations can be measured acoustically by using a particle velocity sensor or Microflown since particle velocity is proportional to surface displacement under specific conditions. Moreover, relative phase information can be acquired by adding an additional static reference sensor. Combining particle velocity with relative phase information across the structure gives a very powerful visualization technique for studying operational deflection shapes (ODS). In this paper a theoretical basis of the measurement principle is presented along with a experimental example. In addition, a discussion focused on the advantages and disadvantages of the particle velocity based scanning method is given.