J. Antunes et al., REMOTE IDENTIFICATION OF IMPACT FORCES ON LOOSELY SUPPORTED TUBES - PART 2 - COMPLEX VIBRO-IMPACT MOTIONS, Journal of sound and vibration, 215(5), 1998, pp. 1043-1064
In a previous paper, techniques were presented, based on response meas
urements at remote locations, for the experimental identification of t
he flexural wave-guide propagation parameters and for recovering the i
mpact forces. Numerical simulations and experiments were presented, fo
r simple isolated impacts. Those basic results showed that such an inv
erse problem can be successfully attempted, and a good agreement was f
ound between direct measurements and the remotely identified impact fo
rces. However, when subject to flow-induced vibrations, the loosely su
pported tubes display very complex rattling motions-with the impact-ge
nerated primary waves completely immersed in countless wave reflection
s travelling between the tube boundaries. As a consequence, the multip
le-impact patterns of tube-support interaction are much more difficult
to identify than isolated force spikes. In this paper, the authors mo
ve a step further towards the identification of impacts for realistic
tube vibrations. To deal with complex vibro-impact regimes, a signal-p
rocessing technique is presented for separating the multiple wave sour
ces? which uses the information provided by a limited number of vibrat
ory transducers. This technique can be applied to both non-dispersive
and dispersive waves and is therefore useful for all kinds of beam mot
ions. Such a method is instrumental in separating the primary impact-g
enerated flexural waves from severe background contamination. This ena
bles the straightforward identification of complex rattling forces at
a loose support. Extensive results are given in order to assert the nu
merical conditioning of the technique used to identify the impact forc
es, the optimal location of the transducers used in the identification
procedure, and the sensitivity of the identification method to noise
contamination. Overall, results are quite satisfactory, as the complex
identified impact forces compare favourably with direct measurements.
(C) 1998 Academic Press.