Abstract: A device and method for the non-contact measurement of dynamic torsion in a rotating shaft using magnetostrictive sensors (MsS). The monitoring and detection system has specially configured magnetostrictive signal detectors that include inductive pick-up coils, in which signals corresponding to localized shaft torques are induced. The basic system sensor utilizes either a permanent DC bias magnet positioned adjacent the rotating shaft or applies a residual magnetic field to the shaft. The techniques described in conjunction with the system are particularly advantageous for on-line monitoring of loaded rotating shafts that are integral parts of power trains, by providing a low-cost and a long-term sensor for acquiring dynamic data of the shaft portion of the machinery system being monitored and/or controlled.

Abstract: A method and apparatus is provided for the sensing, collection, and analysis of information on combustive and mechanical events occurring within an operating internal combustion engine through the measurement of mechanical stress waves present within the engine. The system includes a magnetostrictive sensor placed in mechanical compliance with the engine, preferably the engine block, which detects and translates stress waves into an electrical signal that is filtered and amplified for recording and/or for analysis. Information regarding the frequency, amplitude, and timing changes within the signal is utilized to characterize the ordinary operation of the engine and to identify anomalous events. The system includes a means for maintaining a signal record and comparing signal features with past records for a particular engine or with standard signal features associated generally with certain engine events.

Abstract: A new ultrasonic method for measuring wall thickness and detecting material flaws in natural-gas pipelines, risers, and similar structures. The method is inherently suitable for the task, because it relies on the use of the natural gas as the coupling fluid for transmitting the probing ultrasonic signals into and out of the pipe wall. Furthermore, the method facilitates the operation of the inspection from the inside of the pipe. An experimental apparatus used to demonstrate the technical feasibility of this approach and provide experimental and theoretical evidence that support the claims is described. Significantly, it is shown that by the use of a diplexer, the same transducer can be used to generate and detect the probing ultrasonic signals. The same configuration is used in commercial ultrasonic inspection of oil pipelines where oil is the coupling fluid; but until now this method could not be used in natural gas pipelines due to the low specific acoustic impedance of natural gas.

Abstract: A method and apparatus for the inspection of ferromagnetic and non-ferromagnetic pipes, tubes or other cylindrical shell structures utilizing the magnetostrictive effect to detect defects such as corrosion pits, wall thinning, and cracks within the structure under evaluation. The apparatus and method constitute an active testing application, wherein 1) a transmitting coil element generates a mechanical pulse within a cylindrical shell structure through the magnetostrictive effect and a second coil detects reflected mechanical waves within the pipe, this by the inverse magnetostrictive effect, or 2) a single sensor functions as both transmitter and detector. The present invention also anticipates a passive monitoring application with a detection coil that continuously monitors ferromagnetic or non-ferromagnetic tubes, pipes, etc.

Abstract: A method and apparatus for the nondestructive evaluation of ferromagnetic and non-ferromagnetic materials, particularly wire ropes, cables, and strands, and pipes utilizing the magnetostrictive effect for measuring minute variations in magnetic fields and characterizing these minute variations as indicative of the acoustic/ultrasonic behavior of fractures, cracks, and other anomalies within a substance under evaluation. The apparatus and method contemplate both an active testing application, wherein a transmitting sensor generates an acoustic/ultrasonic pulse within a material through the magnetostrictive effect and a second receiving sensor detects reflected acoustic/ultrasonic waves within the material, again by the inverse magnetostrictive effect. The advantages of utilizing magnetostrictive sensors as opposed to well known piezoelectric sensors lies in the ability to generate and detect acoustic/ultrasonic waves without a direct physical or acoustical contact to the material.

Abstract: A method and apparatus for the nondestructive evaluation of ferromagnetic and non-ferromagnetic materials, particularly wire ropes, cables, and strands, and pipes utilizing the magnetostrictive effect for measuring minute variations in magnetic fields and characterizing these minute variations as indicative of the acoustic/ultrasonic behavior of fractures, cracks, and other anomalies within a substance under evaluation. The apparatus and method contemplate both an active testing application, wherein a transmitting sensor generates an acoustic/ultrasonic pulse within a material through the magnetostrictive effect and a second receiving sensor detects reflected acoustic/ultrasonic waves within the material, again by the inverse magnetostrictive effect. The advantages of utilizing magnetostrictive sensors as opposed to well known piezoelectric sensors lies in the ability to generate and detect acoustic/ultrasonic waves without a direct physical or acoustical contact to the material.

Abstract: Apparatus for detecting flaws in the threaded end of a ferromagnetic pipe is disclosed. The apparatus comprises means for applying a magnetic force to produce a field generally axially through the threaded end of the pipe, first and second means adjacent successive crests of a thread for sensing a generally radial magnetic field and generating a first and second signal corresponding to the sensed magnetic fields, and means for differentially connecting the signals generated by said first and second sensing means, whereby a differential output signal is produced in response to a flaw between the crests of the thread being inspected. The apparatus also comprises means for helically rotating said sensing means to follow a path corresponding to the threads of the pipe, whereby the first and second signals vary with time.A method for detecting flaws in the threaded end of a ferromagnetic pipe is also disclosed.

Abstract: This disclosure relates to a nondestructive method of measuring stress in a ferromagnetic structural material. One method involves the measurement of the change in ultrasonic velocity induced by an externally applied magnetic field; the method enables nondestructively determining the magnitude, the direction, and the sign (i.e., tensile or compressive) of a stress in a ferromagnetic material. The magnetically induced velocity change of an ultrasonic wave is caused by the magnetoelastic coupling in the ferromagnetic material. This magnetically induced velocity change is characteristically dependent on the magnitude and the sign of the stress and also on the relative orientation of the stress, the magnetic field, and the polarization and propagation direction of the ultrasonic wave. The dependence of magnetically induced velocity changes can be utilized for nondestructive stress measurements. In one version, for measuring bulk stresses, either a longitudinal ultrasonic wave or a shear ultrasonic wave is used.