Simulation of damage-features in a lug joint using guided waves

A lug joint is one of the several 'hotspots' in an aerospace structure which experiences fatigue damage. Several fatigue tests on lug joint samples prepared from 0.25 in plate of Aluminum (Al) 2024 T351 indicated a distinct failure pattern. All samples failed at the shoulders. Therefore, in the current study, different notch sizes are introduced at the shoulders and both experimental and modeled active health monitoring with piezoelectric transducers is performed. Simulations of the real time experiments are carried out using FE analysis. The crack geometry and piezoelectric transducer orientation in lug joint samples are kept same both in experiments and in simulation. Results presented illustrate the feasibility of guided waves in interrogating damage in lug joints. A comparison of sensor signals between experimental and simulated signals, in the time-frequency domain, show fairly good correlation. The frequency transform on the sensor signal data yield useful information for characterizing damage. Sensor sensitivity studies using a distance-based outlier technique are conducted to classify sensor data for different damage states. This information can be used in a number of applications including damage localization by reducing redundant sensors, and optimal sensor placement for SHM.