Patent ID: 7215118

Claim:
An apparatus for structural diagnosis comprising; a plurality of ferromagnetic strips attached around a circumference of a member having an arbitrary cross-section with a fixed inclination; a first housing disposed to surround the ferromagnetic strips, the first housing being made of insulating material; a coil wound around the first housing; a second housing disposed to surround the coil at a fixed distance, the second housing being made of insulating material; and a bias coil wound on the second housing, a power source supplying a current to the coil wound around the first housing and the bias coil; and a magnetic field measuring device for measuring the magnitude of a magnetic field in the vicinity of the ferromagnetic strips and a variation of the magnitude of the magnetic field while torsional waves propagate along the member, the magnetic field being induced by applying the current from the power source to the coil wound around the first housing, the torsional waves being generated according to a magnetostrictive effect; wherein the bias coil is adapted to increase the magnitude of the torsional waves responsive to an application of a direct current to the bias coil.