Aircraft manufacturing involves the drilling of a large number of holes for structural joints. The life and proper functioning of the joint can be critically affected by the quality of the hole which generally deteriorates with drill wear. In the use of composite material for the aircraft structure, the “lamination frequency,” associated with the laminated fiber of the material, can be considered to represent the waviness of the hole surface (an aspect of hole quality). The variance associated with this frequency, present in the dynamic nature of the drilling thrust and the hole surface profile, was found to change with the use of the drill. This study presents the possibility of using this change in the lamination frequency content of the drilling thrust for on-line monitoring of the drill condition, through analysis by the Dynamic Data System (DDS) technique.

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