Experimental Validation of Nonlinear Model Tracking with Varying Conditions

Abstract

Mechanical systems can be described with models involving mass, damping, stiffness and nonlinear parameters, albeit with varying complexity. With known healthy model values, investigation of beam failure by crack initiation and propagation can be approached through monitoring model values while the system is excited. This approach uses harmonic excitation and focusses on the nonlinear model value. This experimental testing is performed near the system’s second natural frequency in a thin cantilever beam. Holding continuous sinusoidal forcing, significant shifts in the beam’s nonlinear parameter serve as an early warning of the system’s failure. This study is a continuation of iterative research [Song et al.: Mech. Syst. Sig. Process. 49(1–2), 13–23 (2014)] to verify the integrity and robustness of this particular type of health monitoring in cantilevered beams. This study explores how varying beam geometry, material, excitation frequency, and introducing an additional mass to the system will affect the expected change in the nonlinear parameter as well as how standard beams excited by discretely changing frequencies will give rise to these changes. Results indicate these variables alter the nature of the model, yet still provide significant warning of system failure. In practice, the scope of applicability becomes apparent in both the type of systems and excitations to prevent catastrophic failure.