Structural Health Monitoring of Beams

Abstract

Chapter 3 illustrates the genetic fuzzy system for structural health monitoring of a beam. The cantilever beam structure is fixed at one end and free at the other and can model airplane wings, helicopter blades, and turbine blades, among other things. A finite element model of the undamaged and damaged beam is used to simulate the damaged system. Damage is introduced in the beam by a localized stiffness reduction in accordance with continuum mechanics theory. A genetic fuzzy system is formulated for the beam structure to find the damage location and size from modal data. Initially, the genetic fuzzy system is developed for a uniform beam. It is shown that the method is robust to noise in the data and to missing measurements. The genetic fuzzy system is then illustrated for a nonuniform beam and for a more refined discretization of the damage locations. It is shown that the architecture of the genetic fuzzy system allows for a simple approach for recreating the pattern recognition algorithms as the measurements and outputs change. For each input-output set, a genetic algorithm is used to maximize the success rate of fault isolation for a set of noisy data. The approach is finally illustrated for a non-rotating helicopter main rotor blade using frequency and mode shape data. It is found that the genetic fuzzy system performs very well for the structural health monitoring of beams.