Antal Gasparics

Transient eddy current analysis of pulsed eddy current testing by finite element method

Transient eddy current analysis of pulsed eddy current testing was performed by time-stepping method and Fourier transform method. The characteristics of two methods were evaluated by using a simple model. The accuracy was examined by the comparison of calculated and measured data. The calculated results of the two methods provided good agreement with measured data. However, it was clear that the Fourier transform method provided higher accuracy of amplitude than the time-stepping method. As a three-dimensional problem of pulsed eddy current testing, the TEAM Workshop Problem 27 was analyzed by an edge-element finite element method.

Improving the sensitivity of Fluxset magnetometer by processing of the sensor core

The processing of the sensor core material was investigated on the operation of the Fluxset magnetic field sensor. Static and dynamic magnetic properties were measured, and the signal of the pick-up coil was investigated as a function of processing. The sensitivity and signal/noise ratio of the sensor can be improved significantly by polishing of the ribbon and heat annealing.

Numerical calibration of fluxset probe for quantitative eddy current testing

Fluxset type eddy current probes are used for detecting discontinuities in conducting materials. The measurements obtained by such probes can be used for the reconstruction of the parameters of the detected discontinuity if the output signal of the measurement is uniquely related to the measured field. In this paper a calibration method is presented for the establishment of the relation between the measured magnetic field and the output signal of the probe. The relation is obtained by the optimisation of the parameters of the mapping between the calculated magnetic field distribution and the measured output signal. The magnetic field distribution due to the interaction of the probe and an infinitesimally thin crack located in a conducting plate is calculated numerically by the solution of a boundary integral equation.

Nondestructive Material Evaluation by Novel Electromagnetic Methods

A high sensitivity magnetic field sensor, which has recently be en developed, is applied for non-destructive testing. The sensor can be effectively utili zed for the detection of defects in conducting materials using eddy current testing measurements. The principle of this measuring technique is based on the combination of the detection of changes in the eddy current magne tic field and the variation of magnetic polarization of the sample due to the pr es nce of the defect. The capability of this technique has been demonstrated by measurement s p rformed on different specimens. The sensor was also applied for measuring the magnetic leakage in pla stically deformed, ferromagnetic, low alloy steel samples. High resolution and hig h sensitivity were achieved, strong inhomogeneities were revealed in the investigated sample, and the fi ne structure of the magnetic flux distribution was detected.

Advances in Signal Processing to Reduce Lift-off Noise in Eddy Current Tests

Nowadays, Non Destructive Testing and Evaluation (NDT/NDE) are frequently used to evaluate integrity of manufactured articles in civil or industrial applications. In this framework, Eddy Current Test (ECT) technique has a primary role for inspection of conducting materials. Solution of many related inverse problems requires an accurate comprehension of mea- sured data: it is one of the most challenging problem in this context. Thats why a suitable signal pre-processing is necessary. In this paper, advanced signal processing techniques are evaluated in order to reduce the impact of lift-ofi efiect on the eddy current data. Some hybrid approaches are also depicted, with encouraging results. DOI: 10.2529/PIERS061007215011

B‐H characteristic extraction using devices with non‐uniform field

The paper describes an efficient method to extract the B‐H nonlinear characteristic from the experimental flux‐current Φ‐I data obtained using a non‐uniform magnetic field device. Both functions are monotonically piecewise linear approximated with the same number of breakpoints. The method was successfully applied to characterize the ribbon core material of a fluxset magnetic field sector. In this case the hysteresis loop and the lumped magnetic circuit were extracted. Comparison with experimental results validates the proposed method.

Probe for detecting weakly interacting magnetic nanoparticles

Fluxset magnetic sensor based probes with single and double exciting coils have been developed for detecting weakly interacting, low mass and small size magnetic particles. Test measurements were performed on capsules containing 0.15–13.53 mg magnetic iron oxide particles. It was shown that even 0.7 mg of magnetic nanoparticle of size 30 nm could be detected from a distance of 3.5 mm with reliable signal to noise ratio.

Magnetic imaging in non-destructive testing

Fluxset magnetic sensor based magnetic imaging applications and their benefits are presented in this paper in the scopes of aviation related non-destructive testing applications.

Influence of the core material polishing on the Fluxset sensor's operation

Mechanical, chemical and electrochemical polishing of the sensor core material was investigated on the operation of the Fluxset magnetic field sensor. A significant improvement of the sensitivity was found after proper polishing. The phenomenon was interpreted, taking into account chemical changes in the surface region, the effect of surface roughness on domain wall motion, volume changes in the core material, and the skin effect.

Inspection of diesel engine injectors by several electromagnetic nondestructive methods

Improved eddy current techniques and a method of magnetic hysteresis measurement were applied for nondestructive inspection of thickness of the hardened surface layer of the steel injectors of diesel engines. A monotonic correlation was found with enough sensitivity and acceptable signal/noise ratio between the electromagnetic parameters and the thickness of the layer. Both the hysteresis and the eddy current methods show very similar types of the correlation. Based on these results, practical application of these novel methods can be realized instead of the presently used destructive tests for inspection of the steel injectors of diesel engines.