A method and
system for implementing magnetostrictive sensor techniques for the nondestructive evaluation of pipeline structures. The
system consists of a magnetostrictive sensor instrument unit, a data storage unit, and a plurality of magnetostrictive sensor probes are positioned on an in-line inspection vehicle. The
instrumentation unit includes
electronics for transmitting excitation pulses to a transmitting magnetostrictive sensor probe as well as
electronics for amplifying and conditioning the signals detected by a receiving magnetostrictive sensor probe. The magnetostrictive sensor probes include both plate magnetostrictive sensors and permanent magnets which provide a
DC bias magnetic field necessary for magnetostrictive sensor operation. The transmitting and receiving probes are attached to the in-line inspection vehicle by way of mechanical arms on opposing sides of the vehicle. The mechanical arms are spring loaded and are equipped with rollers which maintain the probes at approximately constant distances from the inside
diameter of the
pipe wall. The method involves generating pulses of
shear horizontal waves of frequencies less than 200 kHz. The transmitting magnetostrictive sensor probe generates a wave that propagates in both directions around the circumference of the
pipe wall from a point adjacent to the transmitting probe. Both
waves are thereafter received at the receiving probe spaced 180 degrees apart from the transmitting probe. Any defect present in the
pipe wall within the circumference being investigated will show up in the received
signal.