PATH LENGTH EFFECTS IN ULTRASONIC TESTING OF BRICKWORK

This paper deals with the application of ultrasonic testing to the problem of assessing the construction quality of loadbearing brickwork. The need for the development of non-destructive test procedures is discussed and the existing literature is briefly reviewed. The potential usefulness of ultrasonic testing using pulsed signals in the 20-100 kHz band is identified. The paper then concentrates on the results of a recent experimental and analytical investigation concerning the influence of path length on the pulse velocity results obtained using standard digital timing equipment with both indirect and semi-direct transducer configurations. It is shown that the results may be strongly influenced by path length. At small transducer separations a consistent initial pulse velocity value, Vi, is obtained but above a critical path length, Lc, the results become slightly less consistent. It is proposed that these longer path results may be represented by an apparent pulse velocity, Va, which is less than Vi, sometimes by a very significant amount. It is shown that the presence of construction defects leads to reductions in both velocity values and that the relative influence on Va tends to be much greater than on Vi. The results of a detailed investigation of the received signal waveforms using digital storage oscilloscopes are used to show that these phenomena are associated with changes in the shape and amplitude of the leading part of the signal pulse. These changes affect the operation of the digital timing equipment. It is suggested, however, that the development of a testing regime capable of identifying Va and Lc, as well as Vi, would provide more reliable information on the condition of a wall, and greater sensitivity to the presence of defects, than the simple procedure of measuring Vi over a fixed short path length. It is further proposed that the measurement of transit times over path lengths significantly greater than Lc may provide the basis for a practicable approach to the assessment of large areas of brickwork. (A) For the covering abstract see IRRD 861706.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0903132206
• Corporate Authors:

  BRITISH INSTITUTE OF NON-DESTRUCTIVE TESTING

  1 SPENCER PARADE
  NORTHAMPTON,   United Kingdom  NN1 5AA
• Authors:
  • HOBBS, B E
  • VARDY, A E
  • ZUBAIR, AKM
• Conference:
  • CONFERENCE PROCEEDINGS OF THE BRITISH INSTITUTE OF NON-DESTRUCTIVE TESTING INTERNATIONAL CONFERENCE, NDT IN CIVIL ENGINEERING 14-16 APRIL 1993, LIVERPOOL UNIVERSITY. VOLUME 2
• Publication Date: 1993

Language

• English

Media Info

• Features: References;
• Pagination: p. 451-68

Subject/Index Terms

• TRT Terms: Conferences; Detection and identification; Detectors; Deterioration; Field tests; Loss and damage; Nondestructive tests; Reinforced concrete; Structures; Test procedures
• ITRD Terms: 3352: Building (structure); 8525: Conference; 1614: Damage; 9115: Detection; 5255: Deterioration; 6226: In situ; 6216: Non destructive testing; 4794: Reinforced concrete; 6288: Test method
• Subject Areas: Bridges and other structures;

Filing Info

• Accession Number: 00644614
• Record Type: Publication
• Source Agency: Transport Research Laboratory
• ISBN: 0-903132-20-6
• Files: ITRD
• Created Date: Apr 18 1994 12:00AM