Vibration based non-destructive evaluation shows promise for damage detection in metal-to-metal adhesive joints. This research investigates an experimental technique to diagnose damage in single-lap adhesive joints subject to cyclical tensile loading. Vibration analysis reveals that damage can be correlated with changes in identified modal damping ratios. Constant amplitude forcing functions are employed to eliminate amplitude-dependent nonlinearities in the dynamic response profiles. Damping estimates obtained from time-domain analyses correlate well with damage magnitudes. Finite element modal analysis of the lap joints supports the experimental results.
Bonded metallic GRID-LOCK ® structures are being adopted for a variety of aerospace applications due to their structural efficiency and damage tolerance. The development of non-destructive evaluation (NDE) methods is necessary to identify bond defects that can lead to failures in these structures. However, this task is complicated by the lack of interior access and complex geometry of GRID-LOCK ® components. In this dissertation, the feasibility of various NDE techniques for detecting the existence, location, and extent of bond defects in GRID-LOCK ® joints is investigated. Experiments are conducted on customized test structures to compare the effectiveness of optical NDE, ultrasonic C-scans and vibration-based damage detection. Finite element analysis (FEA) is used to interpret experimental results and highlight the advantages of candidate methods. The qualitative effectiveness of optical NDE is further investigated using full-field surface slope measurements (shearography). Because accurate characterization of structural defects is critical to flight safety, a quantitative non-destructive evaluation (QNDE) method using artificial neural networks (ANNs) is developed. This method involves the use of radial basis function networks (RBFNs) trained and validated using FEA simulation data. The effectiveness of this QNDE approach is demonstrated using experimental data from a custom-built optical scanning system.ii My dad has never failed to inspire me and my mom has always supported me, so this one is for them.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.