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Comparative studies on phased array ultrasonic, alternating current potential drop and conventional ultrasonic techniques for detection, monitoring and sizing of circumferential fatigue crack growth in pipes
L. Satyarnarayan,
Published in
Volume: 34
Issue: 2
Pages: 104 - 110
This paper reports the comparative study of detection, imaging and sizing of a fatigue crack initiated from an artificially made circumferential starter notch in a stainless steel (SS) pipe of 169 mm diameter and 14.33 mm thickness that was subjected to cyclic bending loads in a four point bending load arrangement using three NDE techniques: Ultrasonic Phased Array, Alternating Current Potential Drop (ACPD) and Conventional Ultrasonics. All the experiments carried out using Omniscan MX Phased Array system were performed using a 64 element contact phased array linear probe of 5 MHz center frequency and phasing it to generate a 45 degree longitudinal wave inside the specimen, while the conventional ultrasonic technique Krautkramer USN 52L equipment used a 45 degree shear wave probe of 4 MHz centre frequency. Both conventional ultrasonics and phased array techniques used the time of flight method to size the defects. The ACPD setup used in this study consists of RMG 4015 hand held straight probe crack depth meter across the notch on the SS pipe specimen. The phased array, ACPD and conventional ultrasonic techniques measurements were made simultaneously and periodically after a predetermined number of fatigue cycles. Beach marks were introduced deliberately by varying the cyclic load amplitude for every 2 mm increase in crack depth. The crack growth estimated using the three techni ques were critically evaluated and compared with the beach marks that were present in the fracture surface.
About the journal
JournalJournal of Structural Engineering (Madras)
Open AccessNo