Ultrasonic Guided Waves for Damage Detection in Cylindrical Geometries for Torsion and Corrosion Defects

Abstract

In the area of Non destructive testing, ultrasonic testing using wave propagation is an emerging field. Ultrasonic testing uses transmission of high frequency sound waves into a material to detect imperfections or to locate changes in material properties. The most commonly used ultrasonic testing technique is pulse echo wherein sound is introduced into a test object and reflections (echoes) are returned to a receiver from internal imperfections. In this works, Negative spike pulse is used as an input signal to sending/receiving transducer at one end of the rod through Pulser/Receiver system and transmitted pulse is received at the same end by same transducer. The wave signatures obtained are analysed using digitizer card. The results obtained from Ultrasonic Testing were in the form of Voltage-Time curves. For different damage types, ideal modes of testing for frequency excitation were selected. Modes of different frequencies were generated and the best modes for the testing of torsion and corrosion defects on different diameter rods were identified. This report presents the use of pulse echo technique to detect effect of corrosion and torsion damage in steel bars. Testing of rods is done in air by placing the transducer in direct contact with one end of rod where the wave travels through the rod from the transducer with the help of couplant (ultrasonic gel). The comparison of signatures in healthy and rods damaged to various extents (both in torsion and corrosion) leads to damage diagnosis.