In this paper, the results of the simulation study to reconstruct the size of the defects from the data obtained using the active thermography technique based on transient induction heating will be presented. Simulations were performed using the finite element model to obtain the temperature data which are then used to reconstruct the radius (r d ) and depth (d d ) of the wall thinning defects in aluminum plate using inversion method. Two cases, coil inner radius less than the defect radius (r c &lt;r d ) and coil inner radius greater than the defect radius (r c &gt;r d ), were considered. The analysis of the sensitivity of coil dimensions to the calculated peak temperature at the observation point was carried out. © 2012 Springer Science+Business Media, LLC.

Krishnan Balasubramaniam

Department of Mechanical Engineering

C V Krishnamurthy

Department Of Physics

ACTIVE THERMOGRAPHY

ALUMINUM PLATES

COIL DIMENSIONS

DEFECT SIZING

Finite element models

Inversion methods

OBSERVATION POINT

Peak temperatures

Simulation studies

Temperature data

TONE-BURST EDDY CURRENT THERMOGRAPHIES

WALL THINNING

finite element method

Defects

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Nondestructive Evaluation

In this paper, an inversion method is proposed to determine simultaneously the electrical and the thermal properties of a given isotropic material from the time-temperature data obtained from tone-burst eddy current thermography (TBET). A multiphysics forward model for computing the surface temperature data was used in a genetic algorithm (GA) based inversion technique to determine the material properties such as electrical conductivity (σ), thermal conductivity (k), density (ρ), and specific heat (Cp) simultaneously. Different trials were carried out initially with simulated temperature data (with and without noise) and then validated with experiments. © 2011 IEEE.

IEEE Transactions on Magnetics

Simultaneous estimation of electrical and thermal properties of isotropic material from the tone-burst eddy current thermography (TBET) time-temperature data

The eddy current Thermography is an evolving non-contact, non-destructive evaluation method with applications especially in aircraft industries. It involves two approaches (a) the volumetric heating (skin depth much greater than the thickness) of the specimen and the observation of additional heating at defect locations due to Joule heating (called eddy-therm) and (b) the use of high-frequency eddy current bursts (skin depth is smaller than the thickness) for the transient surface/near surface heating of the objects and sensing the propagation of a "thermal wave" using a high-sensitivity infrared (IR) camera (tone burst eddy-current thermography (TBET)). In this paper, a study on the optimum frequency of eddy current excitation that will give a maximum temperature rise for a given thickness has been conducted using both modeling and experimental techniques. COMSOL 3.2 was used to solve the coupled equations of electromagnetic induction and heat transfer. The dependency of this optimum frequency (peak frequency) on thickness, electrical conductivity, and thermal response of the sample are studied. The relation between defect size and the coil inner radius is considered. The thermal responses of defective samples obtained by simulation are compared with experimental results. © 2009 Elsevier Ltd. All rights reserved.

NDT and E International

Frequency optimization for eddy current thermography

This paper reports on a Tone Burst Eddycurrent Thermography (TBET) technique that uses short-time bursts of eddy-currents induced in conducting media to generate local heating inside the material. The transient diffusion of the heat inside the material, induced by pulsed/short-time induction heating, is imaged by measuring the transient temperature profiles on the surface of the material. The presence and characteristics of the defects inside the materials changes the surface temperature transients and thus can be used for the nondestructive evaluation (NDE) of conducting materials. Axisymmetric numerical models of the conventional transient thermography technique are used to benchmark the TBET technique. From the temperature profile data, temperature contrast information is obtained for the different defect depths. Temperature contrast data obtained for TBET, in this process, was compared with that obtained from conventional transient thermography data. It was found that the frequency of the eddy-current and, consequently, the skin-depth of the induced field play an important role in the effective utilization of this technique. Simulation details and the experimental results are presented in the paper. Possible advantages of TBET over conventional flash thermography are also discussed and supported by experimental data. © 2008 American Institute of Physics.

AIP Conference Proceedings

Tone Burst Eddy-current Thermography (TBET)

NDT & E International

2D finite element method study of the stimulation induction heating in synchronic thermography NDT

Influence of Some Parameters on the Effectiveness of Induction Heating

Defect sizing simulation studies for the tone-burst eddy current thermography using genetic algorithm based inversion

Journal	Journal of Nondestructive Evaluation
ISSN	01959298
Open Access	No