Structural identification of a cantilever beam with multiple cracks: Modeling and validation

Abstract

This paper presents the structural identification problem of a multiple damaged cantilever beam with hollow circular cross-section. To consider multiple crack effects, the cantilever beam including cracks is considered for six damage scenarios. The problem is solved by the transfer matrix method analytically and the finite element method numerically. In addition, results are validated by experimental measurements. In analytical solution, the cracked Timoshenko beam is treated as an assembly of sub-segments linked by rotational springs to serve the crack's flexibility coefficient. Finite element models are constituted in ANSYS software for numerical solution. Ambient vibration tests are performed to extract the experimental dynamic characteristics using Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI) methods. Measured and calculated natural frequencies and corresponding mode shapes for undamaged and damaged beams are compared with each other. Modal Assurance Criterion (MAC) and Coordinated Modal Assurance Criterion (COMAC) factors are obtained from the mode shapes and two set of measurements to establish the correlation between the measured and calculated values for identification of damage location.