• Journal of the Korean Society for Nondestructive Testing
• /
• v.28 no.2
• /
• pp.205-210
• /
• 2008

Magnetic hysteresis loops of a nickel strip and a Fe-Co alloy strip, which have been used in magnetostrictive strip type guided wave transducers for long range ultrasonic testing of pipelines, were measured and then magnetic property effects of a strip on transducer sensitivity were analyzed. The sensitivity of an optimized Fe-Co strip transducer was superior to that of the nickel strip transducer by a factor of about 30. It was shown that this was mainly attributed to the differences in remanence magnetization and coercivity of the two magnetostrictive materials.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.28 no.5
• /
• pp.416-420
• /
• 2008

In EMAT field, spiral RF coils are much more widely used when compared with solenoid coils. In the field of the magnetostrictive strip transducers for long range ultrasonic testing of cylindrical structures, however, solenoid coils has been used. This seems to be attributed to the difficulty in fabricating low frequency (i.e., large size) spiral coils. In this paper, we describe a method for fabricating spiral coil magnetostrictive strip guided wave transducers from FFC (flexible flat cable). It is demonstrated through a comparison experiment that the spiral coil transducer has much superior performance (sensitivity, SNR, and guided wave direction control capability) than the previous transducer with solenoid coils.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2008.04a
• /
• pp.205-208
• /
• 2008

This paper propose a advanced technique for exciting and receiving the guided torsional wave to detect flaws in pipe systems. There are some difficulties in selecting and exciting of modes by using the nickel strip attached on pipe systems, such as qualification of residual magnetic field and multi-exciting of the unwanted modes etc. In order to there difficulties we propose the new sensor, so called Crossed-coils sensor. We will prove that it is possible to select the modes to be excited and to find a optimal excitation condition for torsional mode by using the proposed sensor.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.18 no.6
• /
• pp.856-862
• /
• 2008

This paper propose a advanced technique for exciting and receiving the guided torsional wave to detect flaws in pipe systems. There are some difficulties in selecting and exciting of modes by using the nickel strip attached on pipe systems, such as qualification of residual magnetic field and multi-exciting of the unwanted modes etc. In order to there difficulties we propose the new sensor, so called Crossed-coils sensor. We will prove that it is possible to select the modes to be excited and to find a optimal excitation condition for torsional mode by using the proposed sensor.