New Magnetostrictive Transducer Designs for Emerging Application Areas of NDE (original) (raw)
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Review of Guided Wave Testing Using Magnetostrictive Transducers
2018
The use of guided waves for long-range inspection of components is a rapidly growing segment of the NDE service business. Magnetostrictive sensors utilizing ferromagnetic strip material for the transduction effect have proven to be very effective for guided wave testing on a variety of components. There is still a demand for enhanced sensor characterization and the development of specific sensor characteristics. A novel magnetostrictive transducer (MsT) utilizing a reversed Wiedemann effect was introduced to the market in 2010 [1] and opened a number of new possibilities in guided wave testing. The most challenging area is structural health monitoring of components operating at elevated temperature. An extremely robust transducer design was developed and tested for this application; it is capable of functioning at high temperatures as well as stresses induced by thermal cycling. Another recent development is an automated omnidirectional probe suitable for screening of large shells s...
Overview and experimental evaluation of magnetostrictive transducers for guided wave inspection
Non-Destructive Testing
This paper provides an overview on the magnetostrictive sensors performances for guided wave inspection and monitoring of pipelines. Initially the basic working principles of guided wave magnetostrictive sensors are presented followed by experimental tests performed on-field and in the laboratory. The results outline the performances of tested transducers together with advantages and drawbacks concerning the use of magnetostrictive sensors for guided wave inspection and monitoring.
Independently of the instrumentation which is used to generate and receive guided waves (GW) in pipes, wave propagation is affected by some factors like pipe geometry (T-branches, welded joints, U-bends), state of integrity (good state or heavily corroded), coating material (paint, PE, FBE, bitumen etc) or surrounding media (soil, water, air). Among other factors, wave attenuation (gradually loss of energy during guided wave propagation), has a remarkable influence on the performances of the guided wave technique. Sensitivity and range of investigation play a key role to describe the quality of Guided Wave non-destructive testing (GW-NDT) of pipes, particularly when the pipe to be tested is buried or coated with a material that produces a high attenuation effect on the propagating waves. In this paper the relationship between wave attenuation and inspection range and sensitivity is discussed considering measured attenuation values for unburied PE coated pipes, unburied bitumen coate...
Research and Review Journal of Nondestructive Testing
Guided wave testing is now a widely accepted method for detection of structural damage in many different types of components, from pipelines to pressure vessels to tanks. Torsional wave modes (T modes) in pipes and shear horizontal (SH) mode guided waves in plates are good candidates for finding areas with generalized corrosion, due to the absence of fluid coupling effects and their lack of dispersion. However, from our field test experience, certain types of defects are difficult to detect with conventional T mode or SH mode guided wave probes. Gradual wall thinning is one such type of defect; another is crack-like defects in or close to welds or penetrations in the pipe. Recently, Southwest Research Institute (SwRI) has developed a new sensor configuration and scanning system that overcomes these limitations. We have recently developed a linear scanning magnetostrictive transducer (MsT) probe system, in which a FeCo strip wound with radio frequency (RF) coils is attached to the st...
Ultrasonics, 2013
As an effective tool to inspect large plates, omni-directional guided wave transducers have become more widely used to form phased-array inspection systems. While omni-directional Lamb wave transducers have been successfully utilized in the systems, omni-directional Shear-Horizontal (SH) wave transducers have not been investigated. In this paper, we propose an omni-directional SH magnetostrictive patch transducer that consists of an annular magnetostrictive patch, a toroidal coil and a permanent magnet. After presenting the unique configuration of the proposed transducer and its working principle, the omni-directivity of the developed transducer is verified through simulations and experiments conducted in an aluminum plate. The frequency characteristics of the proposed transducer depending on the patch size are also investigated as the underlying reference data for future construction of an SH phased-array system.
Sensors, 2021
Ultrasonic guided waves provide unique capabilities for the structural health monitoring of plate-like structures. They can detect and locate various types of material degradation through the interaction of shear-horizontal (SH) waves and Lamb waves with the material. Magnetostrictive transducers (MSTs) can be used to generate and receive both SH and Lamb waves and yet their characteristics have not been thoroughly studied, certainly not on par with piezoelectric transducers. A series of multiphysics simulations of the MST/plate system is conducted to investigate the characteristics of MSTs that affect guided wave generation and reception. The results are presented in the vein of showing the flexibility that MSTs provide for guided waves in a diverse range of applications. In addition to studying characteristics of the MST components (i.e., the magnetostrictive layer, meander electric coil, and biased magnetic field), single-sided and double-sided MSTs are compared for preferential ...
Performance Of Long Range Ultrasonic Inspection Using Magnetostrictive Sensor Guided Wave On Piping
2015
Long-Range ultrasonic Testing (LRUT) Technology was useful for detecting the corrosion and metal loss in pipes. The aim of the LRUT inspection is to test long lengths of pipe rapidly from a single test location with 100% coverage of the pipe wall and to identify areas of corrosion or erosion for further evaluation using other NDT techniques such as radiography or conventional ultrasonic testing. This technique is equally sensitive to metal loss on both the outside and inside surfaces of the pipe. A technique of using Magnetostrictive sensor (MsS) for generation and detection of guided wave is in practical use already. The torsional guided waves generated in pipes by using MsS have great potential to be used as one of the tool in the structural integrity assessment of piping. Varieties of pipe materials are coming in the industry with the advent of new engineering materials with tailored properties. MsS with the low frequency range of ultrasonic guided waves can be extended to be use...
NDT & E International, 2010
The configuration of magnetostrictive transducers for both transmitter and receiver was optimized for the generation and reception of ultrasonic longitudinal guided waves in seven-wire steel strands in a pitch catch arrangement. Three axisymmetric permanent magnets significantly improved the capability of magnetostrictive transducers compared to two permanent magnets, and effectively increased the amplitude of the longitudinal guided wave mode, L(0, 1) at 160 kHz. Experimental results show that the maximum amplitude of a received guided wave signal could be obtained by using a receiver with a three-layer coil in parallel and a transmitter with a three-layer coil in series. The amplitudes of the defect-reflected signal increased by as much as 50% or more as compared with those when both transducers used a single layer coil. As a result, magnetostrictive transducers with an optimized configuration, including permanent magnet distribution and multilayer coil connection, could be efficiently used for the inspection of seven-wire steel strands by using ultrasonic guided waves in a pitch catch arrangement.
NDT & E International, 2016
Recently, a magnetostrictive patch transducer (MPT) by means of the highly magnetostrictive (such as nickel or iron-cobalt alloy) patch attached on the specimen has been applied in nondestructive ultrasonic testing in waveguides. In the study, we proposed a new MPTs array employing a multi-splitting meander coil (MSMC) for generating and receiving longitudinal guided waves in pipes. In the suggested configuration, the directions of the static magnetic field produced by the permanent magnets and the dynamic magnetic field produced by the MSMC are in the axial direction of the pipe. Two finite element models were established to simulate the distribution of the static and dynamic magnetic fields in the patch, respectively. The proposed MSMC was made of flexible printed circuit (FPC), so it could be easily installed on pipe surface. The performance of the proposed MPTs array was experimentally studied. Firstly, it was experimentally verified that the axisymmetric longitudinal guided wave mode, L(0,2), could be effectively generated and received in pipes with the developed MSMC-MPTs array. Secondly, the frequency response characteristics of the developed MSMC-MPTs array were related to D (the distance between adjacent belts of the MSMC). Thirdly, we demonstrated the ability of the developed MSMC-MPTs array for the identification and location of a crack defect in pipes. Finally, we compared the performances of the MSMC-MPTs array and conventional meander coil-MPTs and proved that the signals of the longitudinal guided wave mode could be enhanced by using the developed MSMC-MPTs array.
Generating and detecting torsional guided waves using magnetostrictive sensors of crossed coils
NDT & E International, 2011
In this work, we propose a crossed-coil magnetostrictive sensor consisting of a solenoid coil, a toroidal coil, and a ferromagnetic patch for generating and detecting torsional waves for pipe inspection. We show that the direction of the magnetic field of the ferromagnetic patch can be controlled by adjusting the input current to the toroidal coil. In addition, it is found that the amplitudes of the signals reflected from the pipe end using a crossed-coil sensor are much larger than those using pre-magnetization techniques, and excitation energies are used to generate the torsional waves only. From results on pipes with multiple circumferential notches, any defects larger in diameter than three times the pipe thickness were detected using the crossed-coil magnetostrictive sensor.