Development of enhanced ultrasonic imaging for in-situ inspection of a tension-stressed threaded fastener

Morris S. Good; Robert V. Harris Jr.; James R. Skorpik; Allan F. Pardini; Christopher M. Smith; Robert E. Bowey; Aaron A. Diaz; Brion J. Burghard; Kayte M. Judd; Justus D. Adamson

doi:10.1117/12.387852

9 June 2000 Development of enhanced ultrasonic imaging for in-situ inspection of a tension-stressed threaded fastener

Morris S. Good, Robert V. Harris Jr., James R. Skorpik, Allan F. Pardini, Christopher M. Smith, Robert E. Bowey, Aaron A. Diaz, Brion J. Burghard, Kayte M. Judd, Justus D. Adamson

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Proceedings Volume 3995, Nondestructive Evaluation of Highways, Utilities, and Pipelines IV; (2000) https://doi.org/10.1117/12.387852
Event: SPIE's 5th Annual International Symposium on Nondestructive Evaluation and Health Monitoring of Aging Infrastructure, 2000, Newport Beach, CA, United States

Abstract

A laboratory system was developed that utilized an ultrasonic pulse-echo technique to detect very small cracks emanating from the thread root of a tensile-stressed fastener. Primary benefits were (1) the ability to inspect the fastener without its removal from the structure, (2) much improved detection sensitivity to small cracks, and (3) easy interpretation of data. The fastener of interest had threads with nominal inner and outer diameters of 1.8 cm (0.73 in.) and 2.2 cm (0.86 in.), respectively, and a thread pitch of 3.1 threads per centimeter (8.0 threads per in.). A plastic washer was placed over the fastener nut to shield the nut from ultrasound and thereby eliminate spurious signals. B-scan images provided feedback to align the ultrasonic scanner and fastener for optimal detection sensitivity. A tone-burst pulser-receiver controlled excitation frequency and bandwidth to maintain focal properties, minimize backscatter noise from the base material, and increase penetration into the coarse-grained Inconel. A custom ultrasonic transducer was used to optimize the focal properties over the inspection zone of 2.3 cm to 3.3 cm (0.9 in. to 1.3 in.) from the threaded end of the fastener. A calibration part with four 1.0-mm (0.040-in.) deep notches spanning the length of the inspection zone was used to calibrate distance-amplitude correction and system sensitivity. Custom B-scan and C-scan views were used to present data to the inspector and optimize the signal-to-noise ratio. A direct comparison was made between ultrasonic and destructive test images. Details of system hardware, data- acquisition procedure, analysis, and plans for a portable hand-held system for field inspection are provided.

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Morris S. Good, Robert V. Harris Jr., James R. Skorpik, Allan F. Pardini, Christopher M. Smith, Robert E. Bowey, Aaron A. Diaz, Brion J. Burghard, Kayte M. Judd, and Justus D. Adamson "Development of enhanced ultrasonic imaging for in-situ inspection of a tension-stressed threaded fastener", Proc. SPIE 3995, Nondestructive Evaluation of Highways, Utilities, and Pipelines IV, (9 June 2000); https://doi.org/10.1117/12.387852

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KEYWORDS

Inspection

Ultrasonics

Transducers

Scanners

Ultrasonography

Calibration

Signal to noise ratio

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