ULTRASONIC GUIDED WAVE INSPECTION OF ADHESIVEJOINTS: A PARAMETRIC STUDY FOR A STEP-LAP JOINT

摘要

Adhesively bonded joints are used to connect structural members in aircraft. Whensubject to loads and environmental conditions these joints undergo deterioration. Being loadbearing members, it becomes critical to develop reliable and non-destructive methods forinspecting these adhesive joints. Ultrasonic guided waves, with their mode and frequency tuningpossibilities, form an attractive tool for such inspections. Guided wave behavior as observedthrough dispersion phenomena is dependent on the waveguide dimensions. Since actual structuraljoints in aircraft involve adherends of different thicknesses and materials, and joints of variedoverlap lengths, a robust inspection methodology needs to be tunable for all conditions. Aparametric study showing the effect that some key joint parameters, that is the thickness of theadhesive, overlap length, and material parameters, have on the ultrasonic guided wave behavior ispresented in this paper. In addition, the influence of defects like cohesive weakness, delaminationand kissing bonds and their location on guided wave propagation is investigated. The transmissionof ultrasonic guided wave energy is used as a guideline to select optimal conditions for jointinspection.