COMPUTERIZED SIGNAL PROCESSING FOR DETECTING CRACKS UNDER INSTALLED FASTENERS

This paper describes the development work on a computerized system designed to detect cracks by rotating a shear wave transducer around installed fasteners or bolt holes. Reflected ultrasonic signals from the cracks are digitized in 2 degrees intervals, processed, and displayed in either polar or rectangular coordinates by the computer. Symmetrical noise resulting from an imperfect fit between the bolt and the hole is suppressed by a statistical digital rejection procedure which increases the signal to noise ratio. Corner slots of .051 x .051 and .025 cm and fatigue cracks under installed fasteners have been detected by this computerized system. Two promising methods to compute flaw sizes are also described in this paper. (A) /TRRL/

• Corporate Authors:

  IPC Science and Technology Press Limited

  IPC House, 32 High Street
  Guildford, Surrey  England 
• Authors:
  • Couchman, J
  • Bell, J
  • Noronha, P
• Publication Date: 1976-11

Language

• English

Media Info

• Features: Figures; Photos; References;
• Pagination: p. 256-262
• Serial:
  • Ultrasonics
  • Volume: 14
  • Issue Number: 6
  • Publisher: Butterworth Scientific Limited

Subject/Index Terms

• TRT Terms: Bolts; Calculation; Cracking; Detection and identification; Detectors; Digital computers; Fasteners; Methodology; Rotation; Sensors; Size; Transducers; Ultrasonics
• ITRD Terms: 3888: Bolt; 6464: Calculation; 5211: Cracking; 8673: Digital computer; 9014: Dimension; 9102: Method; 6406: Rotation; 6120: Sensor; 6140: Transducer; 6739: Ultrasonic
• Subject Areas: Bridges and other structures; Construction; Highways; Maintenance and Preservation; I53: Construction of Bridges and Retaining Walls; I61: Equipment and Maintenance Methods;

Filing Info

• Accession Number: 00149693
• Record Type: Publication
• Source Agency: Transport and Road Research Laboratory (TRRL)
• Report/Paper Numbers: Analytic
• Files: ITRD, TRIS
• Created Date: Jun 22 1977 12:00AM