Full Field Frequency Response Functions: a bridge towards NVH applications

Frequency Response Functions allow the description of the input/output relationship between physical quantities in a broad frequency domain; they can be obtained from an experimental set-up or from a numerical model. Dynamic modelling of mechanical parts and structures have relied on transfer functions since the early '60s, having a strong benefit from the advent of Fourier transforms and multi-channel spectrum analysers. Along with the development of these latter, new substructuring, hybrid coupling and analysis techniques have seen a rapid growth and have found wide application in the field of automotive and aerospace industry, becoming the state-of-the-art procedures in challenging design and quality assessment. The use of FRFs have also permitted multi-domain approaches, such as vibro-acoustic or fluid-structure interaction modelling. But they all lacked of high spatial resolution, which, instead, can be of uttermost importance while dealing with high frequency & short wave phenomena in thin-walled components: vibrations, sound emission, strength&fatigue and all the dynamic events that need a qualified spatial resolution to map in detail the physical behaviour of a complex system. The refinement of image based measurements can nowadays give the opportunity to add a high spatial resolution to traditional NVH tools and pursue a re-interpretation of experimental procedures in a renewed spatialbased approach. In this paper some examples of the potentiality of Full Field FRFs are discussed, based on a recent base research experience had at the Schwingungs- und Strukturanalyse / Optical Vibration Measurement Laboratory of the Vienna University of Technology.