Magnetostrictive sensor technology and its applications
TL;DR: A description is given of its various scientific and engineering applications, including the study of wave dispersion in structures, global and long-range inspection of steel pipes and tubes, condition monitoring of machinery such as combustion engines, and onboard sensing of crash events for vehicle safety system operations.
Abstract: The magnetostrictive sensor (MsS) is a type of transducer which can generate and detect time-varying stresses or strains in ferromagnetic materials. In this paper, a general description is first given of the physical principles of the MsS. sensor configuration and instrumentation, and operating characteristics and capabilities. Then a description is given of its various scientific and engineering applications, including the study of wave dispersion in structures, global and long-range inspection of steel pipes and tubes, condition monitoring of machinery such as combustion engines, and onboard sensing of crash events for vehicle safety system operations.
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Abstract: In this paper we review the state of the art in an emerging new technology: embedded ultrasonic non-destructive evaluation (NDE). Embedded ultrasonic NDE permits active structural health monitoring, i.e. the on-demand interrogation of the structure to determine its current state of structural health. The enabling element of embedded ultrasonic NDE is the piezoelectric wafer active sensor (PWAS). We begin by reviewing the guided wave theory in plate, tube, and shell structures, with special attention to Lamb waves. The mechanisms of Lamb wave excitation and detection with embeddable PWAS transducers is presented. It is shown analytically and verified experimentally that Lamb wave mode tuning can be achieved by the judicious combination of PWAS dimensions, frequency value, and Lamb mode characteristics. Subsequently, we address in turn the use of pitch-catch, pulse-echo, and phased array ultrasonic methods for Lambwave damage detection. In each case, the conventional ultrasonic NDE results are contrasted with embedded NDE results. Detection of cracks, disbonds, delaminations, and diffuse damage in metallic and composite structures are exemplified. Other techniques, such as the time reversal method and the migration technique, are also presented. The paper ends with conclusions and suggestions for further work.
243 citations
Cites background or methods from "Magnetostrictive sensor technology ..."
...(1999) proposed a Lamb wave ultrasonic tomography imaging system for aircraft structural health assessment. The acquisition and processing of Lamb wave data uses the image reconstruction method and is based on algorithms developed for cross-borehole tomography. The transducer geometry consists of parallel arrays of transmitters–receivers. The simulated damage was a circular defect with a 2.5 mm diameter in an aluminum plate. The results showed that the method could accurately determine the dimension, shape, and location of defect by reconstructing an area of 30.5 × 30.5 cm(2). Moulin et al. (2003) studied the feasibility of inducing beam steering with embedded rectangular PWAS. A three-element array mounted on a composite plate was used as transmitter of somehow directional beams of S0 Lamb waves, while peripherally placed PWAS were used as receivers. Changes in the signal amplitudes due to damage were observed. Beam steering studies were also carried out by Sundaraman and Adams (2002), Purekar and Pines (2003), and others....
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...(1999) proposed a Lamb wave ultrasonic tomography imaging system for aircraft structural health assessment. The acquisition and processing of Lamb wave data uses the image reconstruction method and is based on algorithms developed for cross-borehole tomography. The transducer geometry consists of parallel arrays of transmitters–receivers. The simulated damage was a circular defect with a 2.5 mm diameter in an aluminum plate. The results showed that the method could accurately determine the dimension, shape, and location of defect by reconstructing an area of 30.5 × 30.5 cm(2). Moulin et al. (2003) studied the feasibility of inducing beam steering with embedded rectangular PWAS....
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...Kwun and Bartels (1998) and Kwun et al. (2002) developed an electromagnetically coupled transducer for SH guided waves using a portable coil and a nickel foil affixed to the structure....
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TL;DR: A variety of state-of-the-art MPT configurations and their applications will be reviewed along with the working principle of this transducer type.
Abstract: A magnetostrictive patch transducer (MPT) is a transducer that exploits the magnetostrictive phenomena representing interactions between mechanical and magnetic fields in ferromagnetic materials. Since MPT technology was mainly developed and applied for nondestructive ultrasonic testing in waveguides such as pipes and plates, this paper will accordingly review advances of this technology in such a context. An MPT consists of a magnetic circuit composed of permanent magnets and coils, and a thin magnetostrictive patch that works as a sensing and actuating element which is bonded onto or coupled with a test waveguide. The configurations of the circuit and magnetostrictive patch therefore critically affect the performance of an MPT as well as the excited and measured wave modes in a waveguide. In this paper, a variety of state-of-the-art MPT configurations and their applications will be reviewed along with the working principle of this transducer type. The use of MPTs in wave experiments involving phononic crystals and elastic metamaterials is also briefly introduced.
200 citations
TL;DR: In this paper, a simplified acoustoelastic formulation of the Pochhammer-Chree vibrations in cylindrical waveguides is derived in the framework of the partial wave representation for guided waves.
Abstract: Health monitoring of steel strands is the subject of much research in the nondestructive evaluation and civil engineering communities. This paper deals with a guided stress wave method for stress monitoring and defect detection in seven-wire strands. A simplified acoustoelastic formulation of the Pochhammer-Chree vibrations in cylindrical waveguides is derived in the framework of the partial wave representation for guided waves. Magnetostrictive transducers are used to excite and detect the waves in the experiments. Results from acoustoelastic measurements on single wires and on strands are presented, showing the feasibility of the method for stress measurement, although an anomalous behavior of the strands at low stress levels remains the subject of current investigation. Improvements to the inherently low sensitivity of acoustoelastic stress measurements are suggested by adding the effect of strand elongation. The role of the strand anchorages is also examined in the context of wave attenuation. Finally, the suitability of the guided wave method for the detection of indentations and broken wires in the strands is demonstrated, including the possibility of inspecting the critical anchored regions.
156 citations
TL;DR: A finite element model of the elementary transducers has been developed and shows that magnetostrictive EMATs directly applied on mild steel plates have comparatively poor performance that is dependent on the precise magneto-mechanical properties of the test object.
Abstract: Guided wave inspection has proven to be a very effective method for the rapid inspection of large structures. The fundamental shear horizontal (SH) wave mode in plates and the torsional mode in pipe-like structures are especially useful because of their non-dispersive character. Guided waves can be generated by either piezoelectric transducers or electro- magnetic acoustic transducers (EMATs), and EMATs can be based on either the Lorentz force or magnetostriction. Several EMAT configurations can be used to produce SH waves, the most common being Lorentz-force periodic permanent magnet and magnetostrictive EMATs, the latter being directly applied on the sample or with a bonded strip of highly magnetostrictive material on the plate. This paper compares the performance of these solutions on steel structures. To quantitatively assess the wave amplitude produced by different probes, a finite element model of the elementary transducers has been developed. The results of the model are experimentally validated and the simulations are further used to study the dependence of ultrasonic wave amplitude on key design parameters. The analysis shows that magnetostrictive EMATs directly applied on mild steel plates have comparatively poor performance that is dependent on the precise magneto-mechanical properties of the test object. Periodic permanent magnet EMATs generate intermediate wave amplitudes and are noncontact and insensitive to the variations in properties seen across typical steels. Large signal amplitudes can be achieved with magnetostrictive EMATs with a layer of highly magnetostrictive material attached between the transducer and the plate, but this compromises the noncontact nature of the transducer.
149 citations
Cites background from "Magnetostrictive sensor technology ..."
...a possible solution to this problem is to attach a highly magnetostrictive material, like nickel or an iron-cobalt alloy, onto the sample [15], [23]; this can be done by adhesive bonding or, in some cases, via shear couplant....
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...a large number of variants to the EmaT configurations described have been reported [11], [15], [22]–[24]....
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TL;DR: In this article, the application of smart materials/sensors for the structural health monitoring (SHM) of civil engineering structures is critically reviewed, where the major focus is on the evaluations of laboratory and field studies.
Abstract: Structural Health Monitoring (SHM) aims to develop automated systems for the continuous monitoring, inspection, and damage detection of structures with minimum labour involvement. The first step to set up a SHM system is to incorporate a level of structural sensing capability that is reliable and possesses long term stability. Smart sensing technologies including the applications of fibre optic sensors, piezoelectric sensors, magnetostrictive sensors and self-diagnosing fibre reinforced composites, possess very important capabilities of monitoring various physical or chemical parameters related to the health and therefore, durable service life of structures. In particular, piezoelectric sensors and magnetorestrictive sensors can serve as both sensors and actuators, which make SHM to be an active monitoring system. Thus, smart sensing technologies are now currently available, and can be utilized to the SHM of civil engineering structures. In this paper, the application of smart materials/sensors for the SHM of civil engineering structures is critically reviewed. The major focus is on the evaluations of laboratory and field studies of smart materials/sensors in civil engineering structures.
110 citations
Cites background from "Magnetostrictive sensor technology ..."
...Based on these phenomena, Kwun and Bartels [83] invented a type of magnetostrictive sensor (MsS) which could generate and detect guided waves in the ferromagnetic materials under testing without direct physical contact to the material surface....
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References
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Book•
01 Jan 1969
TL;DR: In this article, the authors describe the physical fundamentals of ultrasonics and materials up to the most sophisticated methods for nondestructive testing of solid material using ultrasonic waves for defects such as cavities, nonbonding, and strength variations.
Abstract: Nondestructive testing of solid material using ultrasonic waves, for defects such as cavities, nonbonding, and strength variations, is treated in this book from the physical fundamentals of ultrasonics and materials up to the most sophisticated methods. The book is written at a level which should make it accessible to readers with some knowledge of technical mathematics. Physical laws are explained in elementary terms, and more sophisticated treatments are also indicated. After the fundamentals, instrumentation and its application is extensively reported. Tricks and observations from thirty years of experience in the field are included. The third part of the book presents test problems related to special materials or ranges of modern heavy industry, including recent applications such as those in nuclear power plants. This fourth edition features improved presentation of certain fundamental physical facts, updated reports on electronic instrumentation, and new applications in the nuclear and space industries.
1,751 citations
Patent•
01 Aug 1986TL;DR: An ultrasonic apparatus for testing a material comprises an oscillator (10) which generates a selected frequency in the ultrasonic range, and a transducer (1) is connected to the oscillator for applying an ultrasonic signal to the material and for receiving an echo signal back from the material.
Abstract: An ultrasonic apparatus for testing a material comprises an oscillator (10) which generates a selected frequency in the ultrasonic range. A transducer (1) is connected to the oscillator (10) for applying an ultrasonic signal to the material and for receiving an echo signal back from the material. A phase detector (5) receives the echo signal and an in-phase oscillator signal to generate a first display signal, and a phase detector (6) receives a quadrature signal (90° out of phase from the oscillator signal) and the echo signal to generate a second display signal. The first and second display signals are utilised in a visual display, such as a cathode ray tube (8), to generate an image. The image changes according to the phase shift between the ultrasonic signal transmitted into the material and the echo signal, which, in turn, can be utilised to determine the presence and depth of a flaw or boundary in the material.
1,017 citations
TL;DR: In this article, the development of a dry-coupled piezoelectric transducer system for the detection of corrosion in chemical plant pipework using cylindrical Lamb waves is described.
Abstract: The development of a dry-coupled piezoelectric transducer system for the detection of corrosion in chemical plant pipework using cylindrical Lamb waves is described. It is shown that the axisymmetricL(0,2) mode at a frequency of about 70 kHz is an attractive mode to use for longdistance propagation. The results show that a ring of piezoelectric length-expander elements can be used to excite theL(0,2) mode and to suppress all the nonaxisymmetric modes. Tests have been carried out both with the piezoelectric elements bonded to the pipe and fabricated into a simple transducer which was clamped against the pipe. The performance of the dry-coupled system was very similar to that of the bonded elements. In pulse echo tests, the noise floor obtained with the dry-coupled system was less than 1% of the amplitude of the propagatingL(0,2) mode. The drycoupled transducers provide a simple, light, readily detachable system for the long-range inspection of pipework.
235 citations
TL;DR: In this article, a simple and efficient experimental technique was used to observe the dispersion characteristics of multiple longitudinal modes of elastic-wave propagation in bounded solids of various configurations, including a solid cylinder, cylindrical tube, square rod, reinforcing rod and seven-wire strand.
Abstract: Dispersion characteristics of multiple longitudinal modes of elastic‐wave propagation in bounded solids of various configurations were observed using a simple and efficient experimental technique. The technique involves (1) transmitting a short elastic‐wave pulse into the material using a noncontacting magnetostrictive sensor (MsS), (2) detecting transient waveforms of the transmitted wave using another MsS, and (3) performing time‐frequency analysis on the detected signals using the short‐time Fourier transform (STFT). Data acquired from a solid cylinder, cylindrical tube, square rod, reinforcing rod, and seven‐wire strand are given and discussed based on known theories.
54 citations