Pulsed Eddy Current Measurement of Lift-Off

Lefebvre, J. H. V.; Mandache, Catalin

doi:10.1063/1.2184591

Cited by 12 publications

(4 citation statements)

References 4 publications

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“…Generally, pulsed eddy current signals are analysed for many signal features like peak amplitude, peak arrival time, zero crossing time etc. The LOI-based methodology [8,[14][15][16][17] estimates the signal slopes near the Lift-off point of Intersection (LOI) and correlates them to the gap between the sensor face and the test specimen. The LOI-based methodology is preferred over other signal features such as peak amplitude, peak arrival time, and zero crossing time because it is largely immune to changes in electrical conductivity [14].…”

Section: Philosophy Of Measurementmentioning

confidence: 99%

“…The LOI-based methodology [8,[14][15][16][17] estimates the signal slopes near the Lift-off point of Intersection (LOI) and correlates them to the gap between the sensor face and the test specimen. The LOI-based methodology is preferred over other signal features such as peak amplitude, peak arrival time, and zero crossing time because it is largely immune to changes in electrical conductivity [14]. The canned PEC sensors were fabricated and tested at room temperature with varying gaps using stacks of thin SS foils.…”

Section: Philosophy Of Measurementmentioning

confidence: 99%

See 1 more Smart Citation

High-Temperature Creep Measurement in Metallic Alloys Using Pulsed Eddy Current Sensors: Influence of Geometry and Magnetic Properties

Venkatesulu,

Sharma,

Patankar

et al. 2024

I2M

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Due to limited space constraints, the creep measurement of test specimens in material testing reactors is done mostly by time consuming offline techniques viz.: air gauges, diameter gauges, etc. A new compact sensor based on pulsed eddy current testing technique is designed for online creep measurement during mechanical properties testing of metallic alloy specimens for future nuclear reactors. The pulsed eddy current sensors that are positioned opposite to the test specimen measure gaps to estimate creep, by analyzing the slopes of the signals near the Lift-off point of Intersection (LOI) region. The paper discusses the temporal shifts in pulsed eddy current signals when operated at room and high temperatures. Experiments were carried out at room temperature to study the effect of geometry change on test specimens on the linearity and sensitivity of the signals.Similarly, the effect of magnetic test specimens on measurement methodology and sensitivity is also briefed. The results of the study have provided us with confidence in using the online creep measurement sensor technology in material testing reactors with a molten metal coolant medium environment. This technology will help us evaluate the mechanical properties of metallic alloy test specimens, which are intended for use in future generation nuclear reactors.

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Section: Philosophy Of Measurementmentioning

confidence: 99%

Section: Philosophy Of Measurementmentioning

confidence: 99%

High-Temperature Creep Measurement in Metallic Alloys Using Pulsed Eddy Current Sensors: Influence of Geometry and Magnetic Properties

Venkatesulu,

Sharma,

Patankar

et al. 2024

I2M

View full text Add to dashboard Cite

show abstract

“…However, the LOI relies heavily on the structure of the probe and the conductivity of the specimen (Shu et al, 2008). The LOI method also requires the direct measurement of lift-off distance (Lefebvre and Mandache, 2006). Different probe designs are also studied.…”

Section: Introductionmentioning

confidence: 99%

Direct compensation of lift-off oscillation effect in magnetic impedance–based damage detection

Tang

2014

Journal of Intelligent Material Systems and Structures

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Owing to its magneto-mechanical coupling characteristics, a magnetic transducer such as the electro-magnetic acoustic transducer can excite a metallic structure by means of the Lorenz force, and its electrical impedance is actually directly related to the mechanical impedance of the structure. Therefore, the change in electrical impedance measured can be used as an indicator of damage occurrence. As such, this type of magnetic transducer can be used in impedance-based structural damage detection, which features a non-contact advantage. Nevertheless, one key issue is that the coupling between the magnetic transducer and the structure monitored is strongly influenced by the lift-off distance (i.e. the distance from the transducer to the structure) which oscillates as the structure is oftentimes subject to oscillation/movement due to environment disturbance. In this research, we propose a new data analysis approach of transformed impedance that is immune to the lift-off distance oscillation during measurements. This data analysis approach takes advantage of the lift-off distance information embedded in the impedance measurement and is capable of removing the lift-off oscillation effect without explicitly measuring it. By doing so, the damage signature can be highlighted directly. Numerical simulations and experimental validations are carried out to demonstrate the effectiveness.

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“…To reduce the liftoff effect, Giguere and Dubois conducted intensive investigations of lift-off and proposed the Lift-off point of Intersection (LOI), representing a lift-off independent point in the time-domain pulsed eddy-current signals [13] to eliminate the lift-off effects in multilayer structures [14,15]. In 2006, Lefebvre and Mandache investigated the characteristics of lift-off via theory and experiment [16] and proposed LOI slope to accurately measure the non-conductive layer thickness on a conductive substrate [17]. Tian and Sophian proposed the normalisation and two-stage differential process for time response [18].…”

Section: Introductionmentioning

confidence: 99%

PEC defect automated classification in aircraft multi-ply structures with interlayer gaps and lift-offs

Pan

Chen

et al. 2013

NDT & E International

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Pulsed Eddy Current Measurement of Lift-Off

Cited by 12 publications

References 4 publications

High-Temperature Creep Measurement in Metallic Alloys Using Pulsed Eddy Current Sensors: Influence of Geometry and Magnetic Properties

High-Temperature Creep Measurement in Metallic Alloys Using Pulsed Eddy Current Sensors: Influence of Geometry and Magnetic Properties

Direct compensation of lift-off oscillation effect in magnetic impedance–based damage detection

PEC defect automated classification in aircraft multi-ply structures with interlayer gaps and lift-offs

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