An actuator comprises a magnetostrictive element operably connected to a solenoid coil, preloaded to a default length, having an expanded length greater than the default length, and having a compressed length less than the default length. The compressed length of the magnetostrictive element is not less than a length at which permanent mechanical degradation of the magnetostrictive element occurs. An output element is disposed proximate to a terminal end of the actuator and movable between an original position and an actuated position. The coil can be energized or deenergized between a lower level and a higher level for part or all of an expansion or compression of the magnetostrictive element anywhere within the range between the compressed length and the expanded length. The magnetostrictive element can comprise a terbium alloy.

A method of determining a thickness of a region of wall- or plate-like structure which is thinner than a thickness of a surrounding region of the structure due to a cavity in the structure is disclosed. The method comprises comparing a measured time-frequency dispersion map for at least one dispersive guided wave obtained by measuring the structure using guided waves with a reference time-frequency dispersion map obtained by modelling the structure, determining a cut-off frequency, fc, at which the measured time-frequency dispersion map and the reference time-frequency dispersion map differ and calculating the thickness of the thinner region in dependence upon the cut-off frequency.

A downhole acoustic emitter including a support housing with a cavity and ports, in which housing are disposed a rod-type magnetostrictive transducer with an electrical coil on the rods, and an acoustic waveguide in the form of a cylinder which transitions into a tapering cone. The cylindrical portion of the acoustic waveguide is disposed inside the support housing, and the conical portion is disposed outside the housing. The upper end surface of the acoustic waveguide is coaxially joined to the lower emitting surface of the magnetostrictive transducer by soldering, and the acoustic waveguide is joined at its middle portion, which coincides with the zero vibration point of the waveguide, to the support housing by a threaded joint. The downhole acoustic emitter is provided with an emitting element, the upper end of which is coaxially joined to the lower end of the acoustic waveguide by a threaded joint. The magnetostrictive transducer has a length of 200-280 mm and is made of Permendur, and the ports are arranged around the perimeter of the support housing in two rows, the first of which is level with the top turns of the electrical coil of the magnetostrictive transducer, and the second row is level with the bottom turns of the coil. The emitting element is in the form of a cylinder or a prism with a square cross-section.

A downhole acoustic emitter including a support housing with a cavity and ports, in which housing are disposed a rod-type magnetostrictive transducer with an electrical coil on the rods, and an acoustic waveguide in the form of a cylinder which transitions into a tapering cone. The cylindrical portion of the acoustic waveguide is disposed inside the support housing, and the conical portion is disposed outside the housing. The upper end surface of the acoustic waveguide is coaxially joined to the lower emitting surface of the magnetostrictive transducer by soldering, and the acoustic waveguide is joined at its middle portion, which coincides with the zero vibration point of the waveguide, to the support housing by a threaded joint. The downhole acoustic emitter is provided with an emitting element, the upper end of which is coaxially joined to the lower end of the acoustic waveguide by a threaded joint. The magnetostrictive transducer has a length of 200-280 mm and is made of Permendur, and the ports are arranged around the perimeter of the support housing in two rows, the first of which is level with the top turns of the electrical coil of the magnetostrictive transducer, and the second row is level with the bottom turns of the coil. The emitting element is in the form of a cylinder or a prism with a square cross-section.

An electromagnetic acoustic transducer includes a flux guide surrounded by one or more permanent magnets abutting side faces of the flux guide. The magnetic field from the permanent magnets enters the flux guide where repulsion between the magnetic fields directs at least a portion of the magnetic fields toward a test face abutting a test object. The flux density at the test face is greater than the flux density within the originating permanent magnets. An active portion of a coil disposed between the flux guide and the test object contains conductors that are substantially straight, parallel and carry current in the same direction in order to provide substantially mode pure and uni-directionally polarised excitation of shear waves within the test object.

An electromagnetic acoustic transducer includes a flux guide surrounded by one or more permanent magnets abutting side faces of the flux guide. The magnetic field from the permanent magnets enters the flux guide where repulsion between the magnetic fields directs at least a portion of the magnetic fields toward a test face abutting a test object. The flux density at the test face is greater than the flux density within the originating permanent magnets. An active portion of a coil disposed between the flux guide and the test object contains conductors that are substantially straight, parallel and carry current in the same direction in order to provide substantially mode pure and uni-directionally polarised excitation of shear waves within the test object.

Systems and methods for detecting corrosion in pipes are disclosed herein. In one embodiment, an apparatus for detecting corrosion in an object includes an electromagnetic acoustic transducer (EMAT) having a ferromagnetic core and a plurality of permanent magnets arranged peripherally around the ferromagnetic core. The permanent magnets are arranged to produce a magnetic field through the ferromagnetic core. The apparatus also includes a coil between the ferromagnetic core and the object.

An ultrasonic unit manufacturing system and process are based on a universal ultrasonic generator unit that operates interchangeably with either one of piezoelectric and magnetostrictive ultrasonic devices, and optionally as well as with either on-off or power level control footswitches. The ultrasonic units use a generator unit having a detector that determines whether the connected device is piezoelectric or magnetostrictive, and activates the generator for the appropriate piezoelectric or magnetostrictive operating mode. The ultrasonic units so made and methods of using them are also disclosed.

An ultrasonic unit manufacturing system and process are based on a universal ultrasonic generator unit that operates interchangeably with either one of piezoelectric and magnetostrictive ultrasonic devices, and optionally as well as with either on-off or power level control footswitches. The ultrasonic units use a generator unit having a detector that determines whether the connected device is piezoelectric or magnetostrictive, and activates the generator for the appropriate piezoelectric or magnetostrictive operating mode. The ultrasonic units so made and methods of using them are also disclosed.

A metallic diaphragm disk incorporating a piezoelectric material bonded thereto and operatively coupled to a base rim of a housing provides for closing an open-ended cavity at the first end of the housing. At least one inertial mass is either incorporated in or attached to the housing. A plastic film adhesively bonded to at least one of an outer rim of the housing or an outer-facing surface of the disk provides for receiving an adhesive acoustic interface material to provide for coupling the housing to the skin of a test subject.