RESULTS OF THE TEFFMA EUROPEAN FP7 PROJECT: TOWARDS EXPERIMENTAL FULL FIELD MODAL ANALYSIS

The improvements in the electronics of modern cameras have raised the attention on image based technologies also for the measurement of complex vibration patterns for dynamic analyses in a broad extent beyond Holography. The advent of digital cameras has brought ESPI techniques to a recent success. Besides, the production of hi-speed digital cameras has recently raised DIC technique as another competitive technology in the full field domain; the SLDV, thanks to its ability to scan discrete locations over the surface, can also be considered close to the full field technologies. Present dynamic testing and analysis approaches, based on traditional transducers, do not take full advantage of the growing optical measurements, while full field techniques have proved to be increasingly effective in complex dynamic analysis. The potential of three completely different technologies was benchmarked in the TEFFMA project. SLDV, dynamic ESPI and hi-speed DIC were here first deployed in a complex and unique test on the estimation of FRFs with high spatial accuracy from a thin vibrating plate. A peculiar pointwise comparison was addressed by means of discrete geometry transforms to put all the three technologies on trial at each physical point of the surface. These researches numerically evaluated and compared also rotational and dynamic strain FRFs. Thereafter, dynamic stress FRFs can be modelled directly, by means of a constitutive model: spectral fatigue approaches can try to predict the life of a component in many excitation conditions, highlighting benefits and drawbacks of a direct experimental approach to failure & risk assessment. The identification of EMA models highlighted the increasing quality of shapes that can be obtained nowadays from native full field high resolution gears, against that of a scanning system like the SLDV tested. Model updating results were compared between scanning and native full field technologies, with comments and details on the test rig, on the advantages and drawbacks of the approaches.