Finite element model updating using antiresonant frequencies

This paper uses antiresonant frequencies in the finite element model updating of an experimental six-meter aluminum truss and analyzes the physical correctness of the updated model by using it to detect damage. Rigid elements are used to simplify the modeling of welded joints, and their dimensions are used as parameters in an iterative update based on eigenvalue and antiresonance sensitivities. An update using both natural frequencies and antiresonant frequencies is shown to produce a 46% better correlation to experimental frequency response functions (FRFs) than an update that uses only natural frequencies. The antiresonant updated model is used to predict FRFs for the truss in 112 damaged configurations. Pattern classification and curve-fit algorithms for damage detection are tested. The curve-fit method correctly identified damage 92.6% of the time compared to 76.1% for the pattern classifier. The high quality of the model is attributed to the use of rigid elements that are updated using antiresonant frequencies.