V. Arjun

Bio: V. Arjun is an academic researcher from Indira Gandhi Centre for Atomic Research. The author has contributed to research in topics: Eddy current & Boiler (power generation). The author has an hindex of 3, co-authored 5 publications receiving 47 citations.

Optimisation of pulsed eddy current probe for detection of sub-surface defects in stainless steel plates

Abstract: Pulsed eddy current (PEC) technique is used for the detection of sub-surface defects in electrically conducting materials. In order to extend the application of PEC technique for the detection of defects in thick non-magnetic materials, the detection sensitivity of the probe need to be enhanced. Detection sensitivity of the probe mainly depends on the probe configuration. In view of this, optimisation of probe configuration for deeper penetration of magnetic field in the material is carried out through finite element modelling. Present study focuses on model based design optimisation of PEC probe for the detection of sub-surface defects located more than 4 mm from surface in a 8 mm thick AISI type 316 stainless steel plate. The performance of ferrite cored absolute probe, ferrite cored send-receive probe and ferrite cored send-receive probe with outer shielding has been compared and optimised probe has been fabricated. The detection sensitivity of the optimised probe has been studied using machined notches introduced at different depths.

Development of in-bore magnetostrictive transducer for ultrasonic guided wave based-inspection of steam generator tubes of PFBR.

Abstract: An in-bore magnetostrictive transducer is designed for the steam generator tubes of Prototype fast breeder reactor for the generation of L(0,2) modes of frequencies in the range of 250–350 kHz. Towards this, axi-symmetric finite element models are developed to optimize the coil parameters. The optimized length of the transmitter and the receiver coils turns out to be 10 mm (~half the wavelength) for the frequency of 300 kHz. The optimized width of the coils turns out to be 0.46 mm. FE models also show the generation, propagation and reception of L(0,2) modes in the frequency range of 250–350 kHz. The role of skin effect in the magnetostrictive based-generation of L(0,2) modes with frequency is also discussed. A transducer is designed based on the FE results. The transducer is tested for the generation of L(0,2) mode in the frequency range of 250–350 kHz in a 1 m long steam generator tube segment. A good agreement is observed between FE and experimental normalized amplitudes and the times of flight for different frequencies. L(0,2) modes are found to generate and propagate and received, as predicted by the finite element simulations. An excellent agreement is observed between the experimentally measured group velocities with those obtained from the dispersion curves in this frequency range. Experiments show the signal to noise ratio to be better than 15 dB. To ascertain the utility of the transducer in steam generator tubes for the long range testing, L(0,2) mode at 300 kHz frequency is propagated in a 1.5 m long tube. The resulted multiple end reflections amount to the propagation of 51 m distance. To check the capability of detection of defects, a short tube with a full circumferential defect of depth 0.46 mm (20%WT) and a short tube with a pin hole of 1.5 mm diameter are considered. Further, FE results for the case of the axi-symmetric circumferential defect are validated experimentally. For the case of the pinhole (non-axi-symmetric), the experimental signal to noise ratio turns out to be 6 dB, which is only 6 dB lower as compared to that obtained using a piezo based ultrasonic transducer of frequency 300 kHz coupled to the end of the tube.

Development of a High-Sensitive Dual Frequency Remote Field Eddy Current Instrument for Inspection of Ferromagnetic Steam Generator Tubes

Abstract: This paper presents the development of a high-sensitive remote field eddy current (RFEC) instrument for detection of flaws in ferromagnetic steel tubes. The instrument is capable of simultaneously ...

Influence of thermal expansion bend and tubesheet geometry on guided wave inspection of steam generator tubes of a fast breeder reactor

Abstract: Periodic assessment of steam generator tubes of a sodium-cooled nuclear reactor is very crucial for smooth operation of steam generators. To examine the integrity, an in-bore magnetostrictive trans...

Optimization of Geometrical Parameters of a Magnetostrictive Ultrasonic Guided Wave Probe for Tube Inspection

Abstract: Non-destructive examination of steam generator (SG) tubes of Fast Breeder Reactors is of paramount importance. The inspection needs to be carried out from the inner side of an SG tube due to the constraint in accessibility. Recently, the magnetostrictive ultrasonic guided wave (MUGW) technique has been proposed as an alternative for the inspection of SG tubes. As a commercial MUGW probe for small-diameter ferromagnetic tubes is not available, it needs to be designed and developed with optimum parameters. This paper proposes a three-step optimization approach for the development of a MUGW probe, namely optimization of the diameter and length of a permanent magnet (for bias) finite element modeling based, optimization of the width of the transmitter and receiver coils of the probe by empirical modeling and the optimization of the number of turns of the transmitter and receiver coils by equivalent circuit models. A MUGW probe is fabricated and tested experimentally to validate the optimized parameters. Experiments show the validity of the approach in terms of generation, long-range propagation (47.6 m) of L(0,2) mode at 300 kHz, and the required sensitivity (multiple 10% wall thickness deep uniform wall loss circumferential grooves) in SG tubes.

Pulsed Eddy Current Non-destructive Testing and Evaluation: A Review

Abstract: Pulsed eddy current (PEC) non-destructive testing and evaluation (NDT&E) has been around for some time and it is still attracting extensive attention from researchers around the globe, which can be witnessed through the reports reviewed in this paper Thanks to its richness of spectral components, various applications of this technique have been proposed and reported in the literature covering both structural integrity inspection and material characterization in various industrial sectors To support its development and for better understanding of the phenomena around the transient induced eddy currents, attempts for its modelling both analytically and numerically have been made by researchers around the world This review is an attempt to capture the state-of-the-art development and applications of PEC, especially in the last 15 years and it is not intended to be exhaustive Future challenges and opportunities for PEC NDT&E are also presented

A review of some advanced sensors used for health diagnosis of civil engineering structures

Abstract: The developments in structural health monitoring techniques have led to the invention of various sensors that can be effective damage indicator. Due to environmental or electromagnetic effects and need for constant energy source, the traditional sensors are unable to provide accurate and continuous measurements. In light of these events, new and improved sensors have been developed, along with wireless technology, to assist the monitoring process. With the need of detecting more than one damage parameters, multiplexed sensors have been the main interest of researchers. This paper deals with the different sensors used for determination of strain, acceleration and corrosion. A brief comparative study has been performed and presented in the following review paper. Multiplexed Fiber optics sensor have proved quite effective for SHM and proved to be a good competitor with other sensors. Optimum Sensor Placement technique developed for low level damage diagnosis is Iterated Improved Reduced System (IIRS) Method.

Discontinuity inspection in pipelines: A comparison review

Abstract: Today’s main energy sources; natural gas, petrol and petroleum products are transported via pipelines that are safe at long distances. Most of these pipelines are buried and their integrity is highly important. Deformations like corrosions, dents and cracks destruct the integrity of pipeline and they can cause highly dangerous damaging results. Loss of lives, economical losses and environmental pollution can be given as an example of the problems that may occur. Prevention of such adversities before they occur is possible by inspection of pipelines at specific intervals. In recent years, the devices named “Pipeline Inspection Gauge (PIG)” and designed according to Non-destructive Evaluation (NDE) techniques are used for inspection without destructing pipelines. In this study, the importance of pipeline inspection is firstly emphasized and the studies about the inspection of pipelines at literature are examined. In addition, the usage purposes of PIGs, the basics of Non-destructive Evaluation technologies and the samples of applications at pipelines are examined. According to data obtained from the study, suggestions are made about pipeline inspection.

A novel pulsed eddy current method for high-speed pipeline inline inspection

Abstract: High-speed inspection of inner diameter (ID) and outer diameter (OD) surface defects on thick-wall steel pipes is an important aspect to advance the pipeline inline inspection (ILI) in the oil and gas industry. The state-of-the-art ILI methods including magnetic flux leakage (MFL), ultrasonic testing (UT), electromagnetic acoustic transducer (EMAT), eddy current (EC) and pulsed eddy current (PEC) are hardly applicable to practical high-speed pipeline ILI due to the reasons of long inspection time required for sensor response and low detection sensitivity caused by severe motion. New sensing techniques that offer faster inspection speed, deeper signal penetration depth, better detection sensitivity and linearity, as well as capability of ID/OD discrimination are imperatively needed. This paper proposes a novel PEC sensing method to detect and discriminate ID/OD defects by utilizing the conductivity-dependent and permeability-dependent distribution patterns of induced eddy current at the ID surface of steel pipes. For ID defects, the pattern is caused by the discontinuous conductivity distribution, while for OD defects, the pattern is caused by the non-uniform incremental permeability distribution. A pulse-excited current with short width (2.5 μs), low duty cycle (1%) and fast-falling edge (100 ns) is injected into an excitation coil, so that the secondary magnetic field at the fast-falling edge will produce a transient oscillation in a pair of differential pick-up coils. Then, the time-domain transient oscillatory pick-up signal is extended, filtered, amplified, and extracted to be one feature by an envelope detector and an average sample method, which is processed in real-time by the developed probe for facilitating the back-end data recording. Meanwhile, a novel high-speed pipeline inspection gauge (PIG) with a sensor array is developed for field testing to validate the effectiveness of the proposed PEC method that achieved high inspection speed, deep detection depth, superior sensitivity, good linearity, low power consumption, easy implementation, ID/OD discrimination and crack detection capability.

Eddy current detection of subsurface defects for additive/subtractive hybrid manufacturing

Abstract: In this study, an eddy current (EC) detector is integrated in an additive/subtractive hybrid manufacturing (ASHM) process. The detector facilitates in-process inspection and repair operations through material deposition, defect detection, and removal processes layer by layer. A feasibility test is carried out on eddy current detection of subsurface defects in additively manufactured parts by using an EC detector. The study compares the results obtained from the EC detection with those by the X-ray computed tomography and the destructive methods. Experiments and simulations are conducted to investigate the effect of excitation frequency on intensity of the eddy current signal. The effects of residual heat of an additively manufactured specimen and lift-off distance of an EC probe on impedance changes are also investigated. In addition, the effect of defect width on EC signal is analyzed. The study shows that the EC method is capable of detecting subsurface defects in the ASHM parts. It is promising to integrate the EC detection and subtractive manufacturing into additive manufacturing to produce parts with improved quality and better performances.