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Abstract
The feasibility of using NDE methods to detect voids in adhesive-bonded seams of single ply membranes has been under investigation at NIST. This report covers the first phase of a two part study to investigate the applicability of a pulse echo ultrasonic method for this purpose. A prototype pulse echo ultrasonic apparatus, called the field scanner and suitable for testing of single ply seams in the field was developed. A series of laboratory experiments was conducted using the field scanner to investigate: 1) optimal operating conditions, 2) sensitivity and practical limitations for detecting voids, and 3) variables affecting its response. The equipment was found to be effective in maintaining coupling between the transducer and seam specimens. Two 5-MHz transducers (focusing and non-focusing types) were selected as the most suitable for void detection in the seams. Voids incorporated in laboratory seam specimens were readily detected. The results of the Phase 1 investigation provided guidelines on the optimum conditions for use of the field scanner. Although not without limitations, encouraging evidence was obtained indicating that the field scanner should be applicable to inspections of EPDM seams in service. Consequently field investigations are being conducted, as planned, in Phase 2 of the study.
The feasibility of using NDE methods to detect voids in adhesive-bonded seams of single ply membranes has been under investigation at NIST. This report covers the first phase of a two part study to investigate the applicability of a pulse echo ultrasonic method for this purpose. A prototype pulse echo ultrasonic apparatus, called the field scanner and suitable for testing of single ply seams in the field was developed. A series of laboratory experiments was conducted using the field scanner to investigate: 1) optimal operating conditions, 2) sensitivity and practical limitations for detecting voids, and 3) variables affecting its response. The equipment was found to be effective in maintaining coupling between the transducer and seam specimens. Two 5-MHz transducers (focusing and non-focusing types) were selected as the most suitable for void detection in the seams. Voids incorporated in laboratory seam specimens were readily detected. The results of the Phase 1 investigation provided guidelines on the optimum conditions for use of the field scanner. Although not without limitations, encouraging evidence was obtained indicating that the field scanner should be applicable to inspections of EPDM seams in service. Consequently field investigations are being conducted, as planned, in Phase 2 of the study.
Date
11/1990
11/1990
Author(s)
H Watanabe; W Rossiter Jr
H Watanabe; W Rossiter Jr
Page(s)
46
46
Keyword(s)
ultrasonic; EPDM; field inspection; adhesive bonding; NDT non destructive testing; pulse echo; seams
ultrasonic; EPDM; field inspection; adhesive bonding; NDT non destructive testing; pulse echo; seams