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The layer-wise deposition intrinsic to extrusion-based additive manufacturing induces mesostructural features that behave as distributed air gaps and can modify the effective magnetic response of printed cores, an aspect that remains insufficiently documented for soft ferrites. In this work, the inherent impact of Fused Deposition Modeling (FDM) printing paths on the magnetic properties of additively manufactured MnZn ferrite cores is investigated experimentally. Toroidal cores were fabricated using a PIM-like FDM process from a polymer-based pellet feedstock loaded with 50 vol% MnZn ferrite powder. Two deposition routes were compared: concentric and rectilinear patterns. Magnetic characterization reveals a clear influence of the deposition path on the effective magnetic permeability. While moderate differences are observed under low-signal excitation, significant deviations appear at higher excitation levels. These variations are attributed to the oriented inter-bead porosities induced by the FDM process, which behave as distributed air gaps within the magnetic circuit. Additional investigations based on under-extrusion highlight a marked difference in sensitivity between the two deposition strategies, with concentric patterns exhibiting a higher robustness to local variations in material deposition. In contrast, magnetic losses remain only slightly affected by the deposition strategy. These results highlight the deposition path as an additional design parameter for tailoring the magnetic behavior of additively manufactured ferrite components.

Nickel–zinc (Ni–Zn) ferrites are widely used in the fabrication of high-frequency inductors operating above 1 MHz, particularly for filtering applications in power electronics. Ferrite manufacturers can benefit from advancements in additive manufacturing (AM), enabling the production of customised ferrite cores with complex geometries. In this work, an innovating AM process of Ni–Zn ferrites has been set up through a fused filament fabrication (FFF) printing stage from ferrite powder synthesis to sintered component. This proof of concept has been validated by a two-factor sintering design of experiments (temperature, time) and through bulk, microstructural and magnetic characterisations. The results indicate that the proposed process has the potential to achieve densifications of approximately 90% and real permeability values (μ′) in the range of 80 to 130, indicating performance levels comparable to those of conventional manufacturing techniques. The capabilities of the proposed process have been demonstrated by the printing of a ferrite-based 3D Benchy benchmark, highlighting its suitability for advanced component design in power electronics.

The interest of non-destructive testing (NDT) in steel material characterization is growing especially for quality and life cycle control. The Magnetic Barkhausen Noise (MBN) analysis shows an extreme sensitivity to different parameters: steel grade, grain size, microstructure, magnetic domains wall structure, residual stress, surface condition, etc. It is very difficult to distinguish the individual effect of each parameter on the steel MBN signature. This paper attempts to address this problematic by fixing most of these parameters and varying only one parameter of interest (either austenitizing or tempering temperature) to assess the ability of the MBN technique to dissociate the mechanical properties of different martensitic steel grades. The MBN technique presented herein has proven to be able to distinguish high-performance martensitic steel grades when applied according to the proposed experimental protocol.

Nondestructive testing (NDT) of industrial steel products is commonly used to detect defects such as cracks using among other methods, electromagnetic techniques. When properly calibrated, these NDT can be adapted to evaluate the mechanical properties of steels. It is especially of prime importance when rigorous quality control must be achieved for high performance steels. In this context, the proposed article deals with the investigation of the Magnetic Barkhausen Noise (MBN) to characterize the tensile properties of high mechanical performance martensitic steels.

Additive manufacturing provides flexibility in terms of the shapes that can be produced. This work investigates the impact of Fused Deposition Modeling (FDM) printing paths on the magnetic properties of additively manufactured MnZn ferrite cores. Cores with concentric and straight deposition paths were manufactured using a 50%vol MnZn-filled filament. Magnetic characterization has revealed a significant difference in their static permeability. The process induced small air gaps in-between each deposition line, which influences significantly the permeability. This finding can be relevant for power electronics applications for distributed air gaps components.

Electromagnetic non-destructive testing (NDT) of industrial steels is mostly employed to detect defects such as cracks or mechanical properties inhomogeneities. However, NDT can also be employed, when properly calibrated, to evaluate quantitatively these mechanical properties. It is especially of interest when rigorous quality testing must be achieved on finished steel-based products of which mechanical characteristics must be guaranteed. In that context, the proposed work deals with the evaluation of electromagnetic NDT to characterize the tensile properties of high mechanical performance steels.

Les produits tubulaires commercialisés par Vallourec subissent des tests destructifs rigoureux pour s’assurer que leurs propriétés mécaniques soient conformes aux normes et aux spécifications. En particulier, les tubes en acier sans soudure destinés au marché du pétrole et du gaz doivent être des produits fiables et durables. Pouvoir mesurer de manière non destructive certaines des propriétés mécaniques de ces aciers répondrait à un besoin industriel fort. C’est le défi auquel cette thèse veut répondre : mettre en place une méthodologie permettant de mesurer une ou plusieurs grandeurs mécaniques des nuances d’acier Vallourec, à partir de signaux obtenus par des techniques de contrôle non destructives (CND). Afin de décorréler rigoureusement les différentes contributions qui influencent les mesures expérimentales, une analyse détaillée des mécanismes impliqués est nécessaire. L’étude des propriétés mécaniques des aciers étant un domaine extrêmement riche, nous ne nous intéresserons qu’aux nuances d’acier OCTG (Oil Country Tubular Goods). Ces aciers martensitiques sont destinés aux applications de forage, d’extraction du pétrole et du gaz naturel. Aussi, notre attention se porte sur l’évaluation des propriétés suivantes : limite d’élasticité, résistance à la traction, dureté et l’état de contrainte. Pour ce faire, des techniques CND électromagnétiques et ultrasonores pour la caractérisation matériaux des aciers sont mises en place.