M. Dearaujo et J. Antunes, REMOTE IDENTIFICATION OF IMPACT FORCES ON LOOSELY SUPPORTED TUBES - PART 1 - BASIC THEORY AND EXPERIMENTS, Journal of sound and vibration, 215(5), 1998, pp. 1015-1041
Flow-induced vibration of heat-exchanger tube bundles is an important
issue, concerning component life and plant availability. Predictive me
thods have been developed to analyze heat-exchanger tube responses and
wear, for realistic multi-supported tubes and flow configurations. Ex
perimental validation of these methods is currently pursued by several
research groups, with considerable success. However. experiments on v
ibro-impacting tubes involve very carefully instrumented test tubes an
d tube-supports, which is seldom possible in real field components, du
e to space limitations and severe environment conditions. Hence, there
is a need for identification techniques that enable the diagnostic an
d field monitoring of tube-support interaction under real operating co
nditions, using information from motion transducers located far from t
he impact locations. In this paper, the basic theory for the propagati
on of flexural waves is briefly reviewed, and techniques are developed
for the experimental identification of the wave path propagation para
meters and impact forces, from tube response measurements at remote lo
cations. These inverse problems are quite sensitive to the noise conta
mination of measurements. Optimization techniques are used to overcome
these difficulties, and their merits are accessed using extensive num
erical simulations. Then, experiments performed on a long steel beam a
re presented. A simple method is developed to deal with the boundary r
eflections of a wave generated by a single impact. Experimental identi
fication of the wave-path properties, of isolated impact forces and al
so of impact locations is performed. Overall, quite good agreement was
found between directly measured and remotely identified quantities. (
C) 1998 Academic Press.