Linear and nonlinear damage detection using a scanning laser vibrometer

In the past few years, in-operation modal analysis has become a valid
alternative for structures where classic forced vibration tests would
be difficult, if not impossible, to conduct. A disadvantage of this
method is that the excitation forces are unknown. Therefore, not all
modal parameters can still be estimated. As a result, operational mode
shape estimates remain unscaled (dependent on the unknown level of
excitation) what restricts the applicability of operational modal
models. So far, no techniques are available for the correct re-scaling
of operational mode shapes purely based on experimental output-only
data. All known methods involve either a detailed knowledge of the
material characteristics of the test structure (finite element model
approach) or make very restrictive assumptions about the excitation
signal. In this contribution, a sensitivity-based method is proposed
for the scaling of operational mode shapes on a basis of operational
modal models only. (C) 2002 Elsevier Science Ltd. All rights reserved.