Original Date: 10/14/1988
Revision Date: 01/18/2007
Information : Ultrasonic Inspection
Bell Helicopter Textron, Inc. (BHTI) is making extensive use of ultrasonic inspection techniques for the non-destructive evaluation and testing of materials. Depending on part size and geometry, the immersion method, reflector plate method, through transmission method, and non-immersion ultrasonic inspection is used.
Immersion is used on parts having hollow centers, such as rotor blades and fiberglass spars. BHTI has the capability to inspect parts up to 18" x 36" x 25' by use of the immersion method. Parts are completely immersed in water tanks, with the ultrasonic transducer and receiver, on opposite sides of the part, able to traverse the complete distance of the part. Immersion inspection can scan at up to 15 inches per second and is able to detect small voids. It is currently used to inspect the V-22 rotor spindle.
Reflector plate inspection is similar in technique to immersion, but places the transducer and receiver on the same side of the part. A reflector plate is placed on the opposite side of the part and echoes the transducer's signal back to the receiver. This method is able to detect very small voids and porosity, ply gap, and ply misorientation. Engineering personnel inspect test panels using this method in order to optimize lay-up procedures and test standards.
BHTI uses a gantry, non-immersion or squirter method to inspect parts up to 50 feet in length, such as the V-22 upper and lower wing skins. Small voids and porosity of 5% or more are detected in panels up to ½ inch thick, with scanning speeds reaching 20 inches per second.
BHTI developed hand-held, multiple transducer devices called Mobile Ultrasonic Systems (MOUSs), which are used to inspect I-beam stringers. Four MOUS tools use both through transmission and pulse echo transmission to inspect four radii, the web, and four flanges of an I-beam. MOUS tools are attached to a multiplexer, which is connected to the gantry ultrasonic unit. Inspection data is retrieved by an Automation Industries cell controller. Once a scan is complete, the scan data is sent to a Data General Nova 4 computer for analysis and storage on disks.
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