Ebook: Electromagnetic Non-Destructive Evaluation (XXIV)

The 25th International Workshop on Electromagnetic Nondestructive Evaluation (ENDE2022) took place from 13 to 15 June 2022 as a virtual event, organized in Budapest by the Budapest University of Technology and Economics and the Centre for Energy Research, Budapest. The technical organization of the workshop was provided by Diamond Congress Ltd.

This workshop had originally been planned for 2020, but was postponed by two years due to the COVID-19 pandemic, and even in June of 2022, it was held as a virtual event due to the travel restrictions still in force in several countries. This meant that ENDE2022 became the first online event in the quarter-century long history of the workshop series. We do believe that ENDE2022 accomplished its mission of ensuring the continuity of the ENDE series during a difficult time, and our scientific community benefited from this opportunity to gather and share recent results related to electromagnetic nondestructive evaluation.

In total, 26 contributions from 10 different countries were accepted for presentation at the workshop, and 32 attendees participated at the event. At the beginning of the workshop, Sandor Bilicz, the general chair of the workshop, and Christophe Reboud, chair of the International Standing Committee, welcomed participants to the workshop. After that, each presenter was given 15 minutes for their talk, followed by 5 minutes to discuss the presentation. The contributions were organized into 5 sessions over 2 days, chaired by experts of the field as follows:

Analytical and numerical modelling (chair: Antonello Tamburrino)

Inverse problems, imaging and signal processing (chair: Dominique Lesselier)

Advanced sensors (chair: Christophe Reboud)

Non-destructive testing and evaluation (chair: Gui Yun Tian)

Complex material characterization (chair: József Pávó)

Thanks to the technical team of organizers, the implementation of the online platform for the presentations and discussions was of high quality, giving the impression of an in-person event with space for fruitful discussions. The third day of the event was devoted to the online meeting of the International Standing Committee.

Short versions of all presented papers were published electronically in the digest of the workshop. Eleven full papers were accepted after peer-review and are published in this book of proceedings.

We would like to thank again all participants, reviewers, chairs and members of the local organizing committee for their contribution to the success of ENDE2022.

Sándor Bilicz, Szabolcs Gyimóthy and Gábor Vértesy

Editors, ENDE2022

Probability of detection (PoD) models take into consideration one or multiple flaw parameters, say the length, maximum depth, or surface area, and a single flaw signal. However, due to the correlation between the response signals, it might be necessary to consider multiple response signals to know about the flaw. Hence, in this work, we demonstrate the possibility of including multiple correlated flaw signals (features) towards the construction of a PoD curve. The flaw features considered are the peaks of the 3 components of the magnetic flux density i.e. B_x, B_y, and B_z. This is a fully model assisted (FMA) study in which a non-magnetic steel plate, that contains a narrow opening flaw, is inspected by an eddy current probe that induces spatially uniform fields in the conductor in the region of interest. The analysis was performed using the semi-analytical boundary element method.

In this paper we introduce the concept of a free-space dielectric permittivity characterization method. The technique is suited particularly for such cases where the dimensions of the test material is several times larger than the excitation wavelength. The proposed method estimates permittivity using a plane wave excitation and multiple receiver antennas. The received power of the antennas are combined in order to estimate the parameters effectively. The weight factors for the combination are determined using multiple-output multiple-regression. The input data of the regression model is calculated using numerical simulations for the different parameter combinations. Results show that the proposed method yields good results when the conductivity of the material is known in advance, and has a limited use when the complex permittivity has to be estimated.

A set of IF steel specimens, at different states of recrystallisation (commercially cold rolled and annealed to give partially recrystallised and fully recrystallised microstructures) and accordingly different texture components have been used to investigate the measurement and prediction of magnetic anisotropy. A finite element microstructure model that considers crystallographic texture has been used for the prediction of magnetic anisotropy to compare to the measured values, with comparable anisotropy being observed. The results show that the proposed deployable non-destructive approach (U-shaped electromagnetic sensor that can be placed onto a sheet sample) is promising for the quick evaluation of the magnetic anisotropy in IF steels.

The coercivity changes and Barkhausen noise properties of the martensitic stainless steel with a tensile and compressive stress applied by a 4-point bending method was evaluated for aiming nondestructive assessment of residual stress of the steel. Both coercivity and Barkhausen noise signal shows monotonically changes against the applying stress when the materials have different microstructure states.

In this paper we present a modification of an existing analytical model for a long surface crack on a conductive plate. This is actually a thin skin model and the challenge for its successful implementation is the accurate calculation of the magnetic field on the defect-free surface on a conductor. We can now combine analytical expressions with numerical results to calculate the coil impedance changes, due to the defect existence. Using the numerical results by FEM for the coil’s magnetic field into the final impedance change analytical expression we can simulate eddy current probes with complex shape that are difficult to be described analytically.

A novel inductive multifrequency passive resonator is used to sense dielectric objects in the context of breast tumor characterization. It aims to monitor breast tumors evolution wirelessly in the radiofrequency range. This paper shows an electrical equivalent modelling of the proposed sensor and an example of an application consisting of the detection of a 1.5 cm diameter sphere filled with a conductive solution.

Heat and thermochemical treatments of materials are commonly used in mechanical industries as an effective means of optimizing their mechanical properties. The lean towards a 100% quality approach exacerbates the need for nondestructive means to test the quality of treatment processes. In this paper, we will show the potential of electromagnetic methods for such tests through three industrial applications: analysis of nitriding multilayers with 3MA, stress profile evaluation by 3MA and retained austenite ratio by 3MA and Barkhausen Noise.

The aim of this paper is to show a simple method to characterize a common mode choke (CMC). For the accurate 3D modeling of a CMC, it is essential to know the frequency dependent permeability of the core. To establish the electromagnetic properties of the core of the choke, a simple impedance analyzer and a partly disassembled CMC is enough. The impedance measured this way is suitable to express the permeability, that can be subsequently used to build an accurate coupled 3D-circuit model of the CMC. This model can be utilized to examine inductive and capacitive couplings between the choke and other nearby placed filter components, e.g., capacitors.

Array probe design is challenging in remote field eddy current (RFEC) technique due to the exciter and receiver separation. This paper presents the design of a multi-element RFECarray probe for imaging of defects in ferromagnetic steam generator tubes. Systematic investigations of the axial and radial magnetic field distribution at the remote zone are performed to understand their detection sensitivity. The radial magnetic field, showed higher perturbation near defect and hence higher sensitivity. Hence, receiver coiloriented in the radial direction is chosen for the array probe. Further optimization of the number of radial type receiver coils,diameter, height, and angular distance between the coils are carried out after systematic investigations with experimental studies and verified with model results. An array probe with eightnumbers of 4 mm × 4 mm (diameter and height) radial receiver coils placed at 45°apart in the circumferential direction is found to be optimum to detect a1.2 mm diameter through hole. The performance of the radial receiver coil is encouraging for enhanced detection of defects and design of array probe.

Thimble tubes in a nuclear power plant are used to insert detectors to measure the distribution of neutron fluence rate of the nuclear reactor core. It is important to inspect the thimble tubes’ damage timely to avoid accidents and economic losses. However, as the diameter of the tube is only 5mm, it is challenging to develop such a small array probe that suits thimble tubes. This paper presents a new probe with array tunnel magnetoresistance (TMR) sensors and elliptical excitation coil for thimble tube inspection. The probe consists of 8 TMR sensors, which are wire bonded on an elliptical circuit board together with a bare die operational amplifier chip. A magnetic field image is generated by the probe in a scan, which is sensitive to both circumferential and axial defects due to the elliptical excitation. A prototype probe has been developed and tested.

The performance of CFRP is influenced by the proper stacking of various layers of carbon fibres oriented at different angles and by the curing process. In these multi-layer structures, fibre misorientation (off-axis) and fibre waviness can happen during manufacturing, leading to reduced performance and structural failures during operation. High-frequency ECT has demonstrated its capability for detecting the orientation-related features, including fibre orientation and waviness, in previous work. However, the electromagnetic modelling of orientation-related features was not fully explored in the community, which hinders the optimisation of the ECT configuration for achieving high detectability and sensitivity. In this work, finite element modelling is used to determine the ECT response of a planar CFRP component containing multiple plies. The structure of CFRP is modelled by 2D waves as the function of orientation and its conductivity tensor. The virtual ECT test was then implemented in the modelling. Then, the tools of the chain are proposed, including Radon transform, and 2D FFT for orientation characterisation. The simulated and experimental data are validated through the chain’s tools. The results demonstrate that the electromagnetic resistive characteristics of the CFRP structure can be modelled with the proposed approach compared with experimental data. The orientation inversion techniques Radon transform can estimate the orientations from the impedance data. The overall strategy has provided the methodology for modelling the heterogenous EM properties of composites.