SHM of pipes using torsional waves generated by in situ magnetostrictive tapes
TL;DR: In this article, an improved magnetostrictive sensors (MsSs) were used for structural health monitoring (SHM) of hard-to-inspect pipes using polymeric magnetic tape material that is suitable for use in a variety of industries.
Abstract: Long-range, torsional guided waves generated in pipes using magnetostrictive sensors (MsSs) have great potential for applications to the structural health monitoring (SHM) of hard-to-inspect pipes. This paper reports an improved MsS technique (when compared to related techniques currently used for the NDT of pipes) that uses polymeric magnetic tape material that is suitable for use in a variety of industries as an SHM tool for pipes. Improvements include increased efficiency, reduced cost and increased long-term survivability of the sensor system. Transduction efficiency was increased by reducing the sensor eddy current losses and by using a field concentrator strip. For long-term monitoring, a low-cost magnetic oxide based MsS material (video recording tape) having the required magnetic properties was used. The MsS strips were oriented to generate non-dispersive torsional guided ultrasonic waves that propagate long distances with minimal mode conversion. Further, considering both safety and long-term survivability of the sensor, low-power ultrasonic instrumentation was developed and tested. Measurements reported here demonstrate the sensitivity of this sensor to both radial notches (saw cuts) and drilled holes. Results also show that magnetic anisotropy of the strip plays a role in generating torsional waves. It is envisioned that results obtained from the present study will significantly enhance the ability to monitor the long-term structural health of piping systems.
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TL;DR: The generation of omnidirectional Lamb waves by a new magnetostrictive patch transducer (MPT) is presented and the mechanism of the Lamb wave generation and its frequency characteristics are investigated.
Abstract: This work presents the generation of omnidirectional Lamb waves by a new magnetostrictive patch transducer (MPT) and investigates its generation mechanism. Although MPTs have been widely used for wave transduction in plates and pipes, no investigation reports the generation of omnidirectional Lamb waves in a plate by an MPT. For the generation, we propose an axisymmetrically-configured MPT that installs multiple axisymmetric turns of coil outside of a permanent cylindrical magnet located above the center of a circular magnetostrictive patch. After confirming the omnidirectivity of the proposed MPT experimentally, the mechanism of the Lamb wave generation and its frequency characteristics are investigated. It is also shown that the Lamb wave is most efficiently generated in a test plate when its wavelength is equal to two-thirds of the magnetostrictive patch diameter. If this wavelength?patch diameter relation holds, the second radial extensional vibration mode of the patch of the proposed MPT is shown to be the mode responsible for generating the Lamb wave in a plate.
52 citations
TL;DR: The goal of this investigation is to extend magnetostrictive transducer technology for simultaneous identification of the axial and circumferential locations of cracks by using shear horizontal (SH) waves.
Abstract: The lowest-branch torsional guided wave is very effective in pipe damage inspection because of its non-dispersive characteristics, but it cannot be used for the simultaneous identification of axial and circumferential locations of a defect in a pipe. Motivated by recent developments in magnetostrictive transducer technology, which is especially efficient in torsional and shear wave generation, the goal of this investigation is to extend this technology for simultaneous identification of the axial and circumferential locations of cracks by using shear horizontal (SH) waves. Unlike the conventional magnetostrictive patch method using a single complete patch wound around the pipe's circumference, the proposed method segments the patch into several pieces to generate SH waves propagating over the pipe surface. Accordingly, SH waves in a pipe are generated and sensed individually by a meander coil placed separately on each segment. By using two sets of segmented-patch arrays separated by some distance, the cylindrical surface of a pipe can be inspected both axially and circumferentially. After the underlying angular profile of the patch segment is investigated, experiments identifying the axial and circumferential locations of multiple cracks in a pipe are carried out to demonstrate the potential of the proposed methodology.
38 citations
Cites methods from "SHM of pipes using torsional waves ..."
...note that conventionally, a single transducer configuration consisting of a solenoid coil and magnetostrictive patches wound around the circumference of a pipe have been used to generate axially propagating torsional waves [15]–[19]....
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TL;DR: A specially configured meander coil-magnetostrictive patch transducer was developed and successful experimental results of generation and measurement of guided pure torsional waves of up to 2 MHz were achieved.
Abstract: This work is concerned with high-frequency guided torsional wave experiments in the range of 1 to 2 MHz in a cylindrical waveguide. A specially configured meander coil-magnetostrictive patch transducer was developed and successful experimental results of generation and measurement of guided pure torsional waves of up to 2 MHz were achieved. The usefulness of the developed method was demonstrated through a case study to detect a small-sized crack which would be otherwise difficult to identify with a lower-frequency torsional wave.
35 citations
Cites background from "SHM of pipes using torsional waves ..."
...For this reason, the guided torsional wave has received much attention in nondestructive evaluation of cylindrical structures [9]–[14]....
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TL;DR: In this article, a circular magnetostrictive patch transducer (CMPT) with a large magnetostriction along a preferred orientation parallel to the patch's rolling direction was proposed.
Abstract: This paper presents the investigation of a directional magnetostrictive patch transducer (MPT) composed of a highly textured Galfenol (Fe?Ga alloy) patch in the use of ultrasonic guided Lamb wave (GLW) inspection techniques for isotropic planar structures. Recently, the actuation and sensing performance of an MPT using a disc patch made of polycrystalline nickel was reported, based on GLW testing in thin aluminum plates. The nickel-based MPT appeared to have omnidirectional GLW sensitivity in the metallic plate because of the isotropic magnetostrictive nature of polycrystalline nickel with random orientation. In this work, we investigated two viable methods to control and improve MPT?s directional sensitivity for detecting GLWs in metallic plate structures. First, we proposed a circular MPT (CMPT) using the highly textured Galfenol patch with a large magnetostriction of ?270 ppm along a preferred orientation parallel to the patch?s rolling direction. The CMPT exhibited outstanding sensitivity to incoming GLWs along the direction of the patch in a thin aluminum plate. This was mainly due to the unique anisotropic magnetostriction effect of the textured Galfenol patch. In addition to the use of the Galfenol material, we developed a novel cruciform MPT (XMPT) containing four solenoid sensing coils that possessed individual directional sensing preferences, corresponding to the orientations of the sensing coils. The directional sensing performance of the XMPT was initially validated by using the polycrystalline nickel patch with the isotropic magnetostrictive characteristic, exhibiting the remarkable directionality attributes of the individual sensing elements. Of particular interest was that the XMPT combined with the highly textured Galfenol patch demonstrated excellent directional sensitivity corresponding to the Galfenol?s preferred orientation. And the directional sensing feature was noticeably enhanced by incorporating the textured Galfenol patch into the proposed XMPT system.
35 citations
TL;DR: In this article, Li et al. combined multiple computer-aided processes for designing graphene thin film sensors and arrays on composites, including spray-coating, laser-scribing and ink-dispensing.
35 citations
References
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TL;DR: The concept of sensor networks which has been made viable by the convergence of micro-electro-mechanical systems technology, wireless communications and digital electronics is described.
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683 citations
01 Jan 1997
TL;DR: In this article, a general-purpose program that can create dispersion curves for a very wide range of systems and then effectively communicate the information contained within those curves is presented, using the global matrix method to handle multi-layered Cartesian and cylindrical systems.
Abstract: The application of guided waves in NDT can be hampered by the lack of readily available dispersion curves for complex structures. To overcome this hindrance, we have developed a general purpose program that can create dispersion curves for a very wide range of systems and then effectively communicate the information contained within those curves. The program uses the global matrix method to handle multi-layered Cartesian and cylindrical systems. The solution routines cover both leaky and non-leaky cases and remain robust for systems which are known to be difficult, such as large frequency-thicknesses and thin layers embedded in much thicker layers. Elastic and visco-elastic isotropic materials are fully supported; anisotropic materials are also covered, but are currently limited to the elastic, non-leaky, Cartesian case.
485 citations
TL;DR: Magnetic crystal anisotropy and magnetostriction have been measured in various single crystals of ferrites having compositions represented approximately by $M{\mathrm{Fe}}_{2}{\mathrm{\O}}_{4}$, where $M$ stands for Mn, Fe, Co, Ni, and Zn in various proportions.
Abstract: Magnetic crystal anisotropy and magnetostriction have been measured in various single crystals of ferrites having compositions represented approximately by $M{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$, where $M$ stands for Mn, Fe, Co, Ni, and Zn in various proportions. Special attention is given to heat-treatment in a magnetic field.The magnetic anisotropy of cobalt ferrite at room temperature is as high as 4\ifmmode\times\else\texttimes\fi{}${10}^{6}$ ergs/${\mathrm{cm}}^{2}$. Magnetostriction is as high as 800\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$. Magnetic anneal is effective at temperatures as low as 150\ifmmode^\circ\else\textdegree\fi{}C, and causes the hysteresis loop to become square. In polycrystalline material the response to magnetic anneal is a maximum at compositions intermediate between Co${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$ and ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$.The constants for the various specimens are tabulated. Values of the anisotropy constants of Mn${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$ at 20\ifmmode^\circ\else\textdegree\fi{}C and -196\ifmmode^\circ\else\textdegree\fi{}C are the same as those determined from ferromagnetic resonance experiments. At -196\ifmmode^\circ\else\textdegree\fi{}C the constant for ${\mathrm{Ni}}_{0.75}$${\mathrm{Fe}}_{2.25}$${\mathrm{O}}_{4}$ differs markedly from that determined by ferromagnetic resonance; this is to be expected from the relaxation phenomena observed by Galt, Yager, and Merritt.
446 citations
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