Investigation of EMAT Base System for the Detection of Bolt Hole Type Cracks. Part I. Detection of Cracks in the Inaccessible Lower Half of Wing Lap Joints Using EMATS

摘要

The detection of saw slots in an aircraft wing lap joint is demonstrated with EMATS (Electromagnetic acoustic transducers) utilizing 250 KHz horizontal shear acoustic waves reflected from the fastener area. A real-time Fourier transform signal processor was developed and used to gather experimental data and generate plots of power vs. frequency as well as the complex transform. A simple ultrasonics model is described which is capable of explaining many of the features of the experimental data. (Author)