- Author
- Watanabe, H. | Rossiter, W. J., Jr.
- Title
- Pulse-Echo Ultrasonic Evaluation of the Integrity of Seams of Single-Ply Roofing Membranes: Laboratory Evaluation of a Prototype Test Apparatus.
- Coporate
- Takenaka Corp., Tokyo, Japan National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Naval Facilities Engineering Command, Port Hueneme, CA
- Report
- NISTIR 4424, December 1990, 46 p.
- Distribution
- Available from National Technical Information Service
- Keywords
- adhesive-bonding | EPDM rubber | field inspection | membranes | nondestructive testing | pulse-echo method | roofing | seams | ultrasonics
- Abstract
- The feasibility of using NDE (non-destructive evaluation) methods to detect voids in adhesive-bonded seams of single-ply membranes has been under investigation at the National Institute of Standards and Technology (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 speciments. 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.