Biblio

Eddy Current Pulsed Thermography (ECPT) is widely used in Nondestructive Testing (NDT) of metal defects where the defect information is sometimes affected by coil noise and edge noise, therefore, it is necessary to segment the ECPT image sequences to improve the detection effect, that is, segmenting the defect part from the background. At present, the methods widely used in ECPT are mostly based on matrix decomposition theory. In fact, tensor decomposition is a new hotspot in the field of image segmentation and has been widely used in many image segmentation scenes, but it is not a general method in ECPT. This paper analyzes the feasibility of the usage of tensor decomposition in ECPT and designs several experiments on different samples to verify the effects of two popular tensor decomposition algorithms in ECPT. This paper also compares the matrix decomposition methods and the tensor decomposition methods in terms of treatment effect, time cost, detection success rate, etc. Through the experimental results, this paper points out the advantages and disadvantages of tensor decomposition methods in ECPT and analyzes the suitable engineering application scenarios of tensor decomposition in ECPT.

Very sensitive magnetic instruments on the JUICE spacecraft require an extremely low magnetic field emission of the various subsystems. The JUICE solar array includes a photovoltaic assembly and various mechanisms with a magnetic signature. The design of the photovoltaic assembly has been optimised not only with respect to magnetic moment, but also with respect to the emitted magnetic field, by applying the so-called back-wiring technique, alternating string polarity etc. The remanent magnetic field of the mechanisms (hinges, eddy-current damper, hold-down & release mechanism) was tested including a process for demagnetisation. In addition, the temperature coefficient for the magnetic moment was measured, down to the operational temperature of -130°C. The eddy-current damper was also subjected to a field-induced magnetisation test. All the contributors were included in a model to calculate the magnetic field at the instrument location.

This article deals with the estimation of magnet losses in a permanent-magnet motor inserted in a nut-runner. This type of machine has interesting features such as being two-pole, slot-less and running at a high speed (30000 rpm). Two analytical models were chosen from the literature. A numerical estimation of the losses with 2D Finite Element Method was carried out. A detailed investigation of the effect of simulation settings (e.g., mesh size, time-step, remanence flux density in the magnet, superposition of the losses, etc.) was performed. Finally, calculation of losses with 3D-FEM were also run in order to compare the calculated losses with both analytical and 2D-FEM results. The estimation of the losses focuses on a range of frequencies between 10 and 100 kHz.