Detection of back-side pit on a ferrous plate by magnetic flux leakage method with analyzing magnetic field vector

Tsukada, Keiji; Yoshioka, Mitsuteru; Kawasaki, Yoshihiko; Kiwa, Toshihiko

doi:10.1016/j.ndteint.2010.01.004

Cited by 35 publications

(14 citation statements)

References 21 publications

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“…Therefore, if these two types of features are inspected, surface topography can also be easily measured accordingly. In this case, by using magnetic sensors to directly induce the magnetic features with a certain liftoff distance above the measured surface, the corresponding surface topography can be inspected and therefore be evaluated [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]. Naturally, a non-contact magnetic inspection and evaluation methodology is provided here by using magnetic sensors such as Halls or magneto-resistive units with a certain liftoff distance to directly scan the corresponding magnetic characters caused by different surface topography, concave or bump, for instance, and then, the picking-up signals are processed through a data processing system where the surface topography is reflected ultimately, as shown in Figure 4.…”

Section: Ndtande Methodology For Surface Topographymentioning

confidence: 99%

A NDT&E Methodology Based on Magnetic Representation for Surface Topography of Ferromagnetic Materials

Sun¹,

Liu²

2016

Non-Destructive Testing

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Accurate evaluation is the final aim of nondestructive testing (NDT). However, the present electromagnetic NDT methods are commonly used to check the existence of defects, and all the tested targets only consist of concave defects (i.e., section-loss defects), such as holes, cracks, or corrosions, failing to evaluate the tested surface topography, which mainly consists of concave-shaped and bump-shaped features. At present, it is accepted that the commonly observed signals of the defects mainly manifest themselves in a single-/doublepeak wave and their up/down directions of the peak wave can be easily changed just by changing the directions of either applied magnetization or pick-up units even for one defect. Unlike the present stylus and optical methods for surface topography inspections, a new electromagnetic NDT and evaluation (NDT&E) methodology is provided based on the accurate magnetic representation of surface topography, in which a concaveshaped feature produces "positive" magnetic flux leakages (MFLs) and therefore forms a "raised" signal wave but a bump-shaped feature generates "negative" magnetic fields and therefore leads to a "sunken" signal wave. In this case, the corresponding relationships between wave features and surface topography are presented and the relevant evaluation system for testing surface topography (concave, bumped, and flat features) is built. The provided methodology was analyzed and verified by finite element and experimental methods. Meanwhile, the different dimension parameters of height/ depth and width of surface topography are further studied.

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Section: Ndtande Methodology For Surface Topographymentioning

confidence: 99%

A NDT&E Methodology Based on Magnetic Representation for Surface Topography of Ferromagnetic Materials

Sun¹,

Liu²

2016

Non-Destructive Testing

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“…The measurement of small, low-frequency magnetic fields is critically important in several industrial fields [ 1 , 2 , 3 ]. Magnetoresistive (MR) sensors, such as anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunnel magnetoresistance (TMR) sensors, are considered promising candidates for magnetic sensor applications.…”

Section: Introductionmentioning

confidence: 99%

Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical Characteristics

Jin

Wang

Fujiwara³

et al. 2020

Sensors

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Thanks to their high magnetoresistance and integration capability, magnetic tunnel junction-based magnetoresistive sensors are widely utilized to detect weak, low-frequency magnetic fields in a variety of applications. The low detectivity of MTJs is necessary to obtain a high signal-to-noise ratio when detecting small variations in magnetic fields. We fabricated serial MTJ-based sensors with various junction area and free-layer electrode aspect ratios. Our investigation showed that their sensitivity and noise power are affected by the MTJ geometry due to the variation in the magnetic shape anisotropy. Their MR curves demonstrated a decrease in sensitivity with an increase in the aspect ratio of the free-layer electrode, and their noise properties showed that MTJs with larger junction areas exhibit lower noise spectral density in the low-frequency region. All of the sensors were able detect a small AC magnetic field (Hrms = 0.3 Oe at 23 Hz). Among the MTJ sensors we examined, the sensor with a square-free layer and large junction area exhibited a high signal-to-noise ratio (4792 ± 646). These results suggest that MTJ geometrical characteristics play a critical role in enhancing the detectivity of MTJ-based sensors.

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“…Anomalies such as cracks in the path of the magnetic flux will produce a leakage, and this leakage can be detected by magnetic sensors. The MFL technique has shown a better detection performance not limited to surface cracks [31]. However, the use of the electromagnet yoke and high current to saturate the sample magnetisation results to a size increase of the MFL system.…”

Section: Introductionmentioning

confidence: 99%

Design of Eddy Current Testing Probe for Surface Defect Evaluation

Saari

Nadzri

Aiman

et al. 2019

IJAME

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Early detection of defects in metallic components used in infrastructure is crucial to ensure their safety and reliability. This paper presents a development of a small eddy current testing (ECT) probe for evaluation of sub-millimetre surface defects. The ECT probe is developed in a planar differential using sensitive anisotropy magnetoresistance sensors, and the signal amplification is achieved by a home-made instrumentation amplifier. The developed ECT probe is evaluated by performing phase sensitive measurement of the magnetic responses of sub-millimetre surface slits at the excitation field of 200 Hz and 10 kHz. Compared to the real component of the magnetic response, the imaginary component can be used to identify the existence and position of the slits based on the signal intensity change caused by the induced eddy current. The spatial distribution of the magnetic response measured by the ECT probe can be used to estimate the dimension of the slit. It is expected that the developed ECT probe can be utilised for assessment of sub-millimetre surface defect.

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Detection of back-side pit on a ferrous plate by magnetic flux leakage method with analyzing magnetic field vector

Cited by 35 publications

References 21 publications

A NDT&E Methodology Based on Magnetic Representation for Surface Topography of Ferromagnetic Materials

A NDT&E Methodology Based on Magnetic Representation for Surface Topography of Ferromagnetic Materials

Detection of Small Magnetic Fields Using Serial Magnetic Tunnel Junctions with Various Geometrical Characteristics

Design of Eddy Current Testing Probe for Surface Defect Evaluation

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