Publications

In this study, a ZrO2 thin film was deposited onto a Ti6Al4V substrate using the Oblique Angle Deposition (OAD) technique. The influence of the substrate/Zr target an-gle (15°, 30°, 45°, and 60°) was investigated, with a fixed azimuthal orientation (Phi) of 180°. The primary objective of this work is to develop and characterize novel biocompatible coat-ings for hip prosthesis implants with a complex 3D spherical geometry. The OAD method enables thin film deposition on such geometries and enhances understanding of how the par-ticle incidence angle affects the surface morphology and microstructure of zirconium oxide (ZrO2) thin films. This study combines an experimental approach DC magnetron sputtering with a multi-scale numerical approach using Monte Carlo codes (SRIM, SIMTRA, and NASCAM). The structure, texture, and growth of the ZrO2 coatings were analyzed via X-ray diffraction (XRD), while microstructure and surface morphology were examined using scan-ning electron microscopy (SEM). Hardness and Young’s modulus were determined through nanoindentation testing. Results indicate that increasing the oblique angle leads to a decrease in hardness. Experimental and numerical findings complement each other, offering deeper insight into the deposition phenomena. SIMTRA simulations closely replicate experimental observations: a higher number of incident particles results in increased coating thickness. Additionally, the film thickness decreases with increasing substrate inclination angle. The microstructure of ZrO₂ thin films is strongly influenced by substrate orientation, and coated substrates demonstrate superior performance compared to their uncoated counterparts.

Introduction Adolescent Idiopathic Scoliosis (AIS) is classically evaluated through static X-rays and health-related quality of life questionnaires that do not reflect the functional limitations of patients during daily life activities, such as walking. The aim was to investigate kinematic strategies in non-operated AIS with different types of curvature during walking using 3D gait analysis. Methods 13 AIS with Lenke 5 (major Cobb: 23 ± 8°), 30 AIS with Lenke 1 (major Cobb: 40 ± 14°) in addition to 24 controls underwent biplanar X-rays followed by 3D gait analysis. The kinematic parameters of the head, trunk, spinal segments, pelvis and lower limbs were compared between groups. Results AIS Lenke 5 had a lumbar segment bending while walking (T12L3-L3L5: 5 ± 7° vs. -3 ± 7° in controls) to the concave side of the scoliosis. They walked with an increased pelvic frontal mobility (12 ± 3° vs. 9 ± 3°) and internal rotation of the right foot (-2 ± 6° vs. -11 ± 8°; all p < 0.05). AIS Lenke 1 increased their thoracic & lumbar segment bending to the concave and to the opposite side respectively (T6T9-T9T12: -4 ± 9° vs. 1 ± 4°; T12L3-L3L5: 8 ± 12° vs. -2 ± 7°). However, they tended to reduce their lumbo-pelvic mobility (7 ± 5° vs. 12 ± 5°; all p < 0.05). Conclusion In response to their inherent lumbar stiffness and bending, AIS Lenke 5 patients tended to increase their pelvic frontal mobility and to develop a homolateral internal foot rotation, ensuring a dynamic alignment during gait. AIS Lenke 1, by producing opposite bending movement at the thoracic and lumbar segments, tended to reduce their lumbo-pelvic mobility and ensure coronal dynamic alignment.

This paper investigates the influence of substrate grain size on the behavior of a multilayer CrN/CrAlN coating, with the bilayer thickness varying across the cross-section in the range of 200–1000 nm. The substrate tools were made of WC-Co sintered carbide with three different grain sizes. The coatings were subjected to mechanical and tribological tests to assess their performance, including nanohardness, scratch resistance, and tribological testing. The coating’s roughness was measured using a 2D profilometer. Additionally, the chemical composition and surface morphology were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX). The durability tests were performed on an industrial CNC machine tool on the particleboard. The results revealed that tools with ultra-fine nano-grain (S) and micro-grain (T) WC-Co substrates exhibited a significant increase in tool durability by 28% and 44%, respectively. Significant differences in the microgeometry of the substrate U, especially in relation to the tool based on substrate S, explain the lack of improvement in its durability despite the use of a multilayer coating.

This study investigates the influence of void shape and orientation on the Forming Limit Diagrams (FLDs) of porous materials with non-quadratic anisotropy. The constitutive framework integrates the Gologanu–Leblond–Devaux (GLD) damage model, which accounts for void morphology, with Barlat’s YLD-2004-18p non-quadratic yield criterion to capture metal matrix plastic anisotropy. The combined GLD-YLD model is further coupled with the Marciniak–Kuczyński (M–K) imperfection approach to predict FLDs for anisotropic sheet metals. Results demonstrate that void morphology considerably affects formability, with prolate (needle-like) voids enhancing material ductility, as compared to oblate (plate-like) voids, while spherical voids yield an intermediate behavior. Furthermore, the study highlights that the impact of material orientation on formability involves a complex interplay of several factors, which include coupled matrix-induced and void-shape-induced anisotropy, the relative angle between the rolling direction and void orientation, and void nucleation mechanism. The model predictive capabilities are assessed against experimental FLD data for two aluminum alloys. Although these alloys show only slight sensitivity to void morphology, due to low porosity, the void shape-dependent anisotropic GLD-YLD model better captures the experimental trends as compared to the undamaged isotropic von Mises model, which overly overestimates formability on the right-hand side of FLD. The role of isotropic hardening is also examined, which shows that higher hardening improves formability, and the effect is smallest for oblate voids under balanced biaxial loading. These findings underscore the importance of incorporating both damage and matrix-induced anisotropy in constitutive modeling for accurate FLD prediction.

A novel multiscale computational framework based on Crystal Plasticity Finite Element (CPFE) modeling is proposed to investigate the effect of grain size on the mechanical behavior and ductility limits of thin metal sheets, featuring both uniform and gradient grain structures. This approach relies on designing unitcell models that reflect the microstructural characteristics of thin metal sheets. The overall response of the unit cell is obtained from that of its single crystal constituents using the periodic homogenization scheme. At the single crystal level, the mechanical behavior is modeled within a finite strain, rate-independent plasticity framework, where the plastic flow is governed by the classical Schmid law. The effect of individual grain size is incorporated at the single crystal scale by adjusting the critical resolved shear stress (CRSS) evolution, using a combination of the microscopic Hall–Petch relationship and a dislocation density-based hardening model. To efficiently solve the single crystal constitutive equations, a return-mapping algorithm coupled with the Fischer–Burmeister complementarity function is developed and implemented into ABAQUS/Standard through a user-defined material subroutine (UMAT). At the macroscopic level, the ductility limits are predicted by the Rice bifurcation theory. The performance of the proposed strategy is validated through a series of polycrystalline aggregate simulations. The numerical results demonstrate a significant influence of grain size on both the macroscopic strength and ductility limits of polycrystalline aggregates. Additionally, the introduction of gradient grain structures is shown to substantially enhance both strength and ductility. These findings provide valuable insights for optimizing material performance in engineering applications.

Inconel 718 alloy is used for high‐temperature industrial applications in its optimized multiphase metallurgical state. Nevertheless, the machining of Inconel 718 alloy becomes problematic and challenging. One alternative consists of developing a new material design strategy based on the metallurgy of high‐entropy alloys (HEAs). These alloys have become a hotspot in the field of innovative high‐temperature metallurgy toward the improvement of the alloy's manufacturability and thermomechanical properties. This study aims at designing, elaborating, and characterizing a new class of alloys with increased entropy, referred to as: “Inco‐like.” The mechanical responses of the alloys, in terms of hardness, have been analyzed using an indentation test at a wide range of temperatures. The dry machinability of the developed alloys has been performed and compared with that characterizing the Inconel 718 in terms of several machining features. Finally, the phases of the studied alloys have been analyzed using metallurgical investigations. The experimental findings and comparisons underscore the advantages of the high‐entropy strategy in terms of tool wear reduction and cutting tool durability. The results demonstrate that the Inco‐like HEA retains a significantly higher hardness of 291 Hv at 800 °C, compared to 160 Hv for Inconel 718 at the same temperature.

Plant fibres are promising reinforcements for bio-composites in additive manufacturing, but their use as long fibres remains limited, often reduced to short particles that underuse their potential. This study presents a customised yarn design that not only maintains fibre alignment parallel to the yarn axis but also ensures core resin impregnation. Commingling and wrap spinning techniques were used to produce four flax/PLA yarns with varying compositions. The manufacturing process and printing of unidirectional composite specimens are detailed. Tomography revealed up to 3.3 times lower intra-yarn porosity thanks to commingling, and tensile tests showed a modulus increase by a factor of 2.1 compared to similar previous works using conventional twisted yarns. These results pave the way for broader use of long flax fibres in 3D printing.

This paper proposes a novel methodology of the topology optimization method considering eddy current effects. The method is applied on chip inductors modelled by the Finite Element Method (FEM). Aiming to meet a specified inductance value while minimizing eddy current losses, we employ a density-based approach to construct a continuous material distribution. The derivative of the objective function with respect to the material distribution is obtained using the adjoint variable method, then the material layout is iteratively updated via the L-BFGS-B algorithm. The proposed framework is validated on both single-turn and multi-turn inductor structures, achieving designs that satisfy the target performance within a limited number of iterations. A key innovation of this work lies in the integration of field-circuit coupling into the topology optimization framework, enabling the analysis of inductors under complex coil configurations involving both series and parallel connections. Additionally, we present an original derivation of the sensitivity formulation associated with the inductance value ensuring that the optimized inductance meets the design specification.

This research focuses on the development and experimental validation of a novel printed piezoelectric transducers network employed on a foreign object damage panel substructure of an aircraft engine fan blade. The main goal of the work is to leverage the screen printing technology to fabricate arrays of piezoelectric transducers and ultimately employ these transducers for operations, enabling the development of structural health monitoring methods for the panel. The printed transducer is made up of a piezoelectric layer sandwiched between two silver electrodes, each printed in a controlled manner. Upon printing and drying of the layers, the transducers undergo polarization. The electromechanical behaviour of the printed transducers, characterized using impedance measurements, exhibits high repeatability, thus indicating its potential for large scale industrial deployment. Following this, it is demonstrated that the transducers are capable of accurately sensing impact, which is one the most common yet critical sources of damage to an engine fan blade. It is also shown that the printed transducers are able to detect acoustic emission events. The ability of the printed transducers to actuate and sense guided wave signals over a range of ultrasonic frequencies is also demonstrated. Furthermore, apart from the noticeable advantages of the non-intrusive nature, and negligible weight as compared to their traditional ceramic counterparts, the printed piezoelectric transducers can potentially be integrated into the manufacturing process in the future, and the presence of transducer arrays ensures the availability of other transducers in case of an individual failure during service. This innovative printing technology for PZT transducer networks thus holds significant promise in bridging the gap between research advancements and the industrial implementation of SHM technology.

This research focuses on the development and experimental validation of a novel printed piezoelectric transducers network employed on a foreign object damage panel substructure of an aircraft engine fan blade. The main goal of the work is to leverage the screen printing technology to fabricate arrays of piezoelectric transducers and ultimately employ these trans- ducers for operations, enabling the development of structural health monitoring methods for the panel. The printed transducer is made up of a piezoelectric layer sandwiched between two silver electrodes, each printed in a controlled manner. Upon printing and drying of the layers, the transducers undergo polarization. The electromechanical behaviour of the printed transducers, characterized using impedance measurements, exhibits high repeatability, thus indicating its potential for large scale industrial deployment. Following this, it is demon-strated that the transducers are capable of accurately sensing impact, which is one the mostcommon yet critical sources of damage to an engine fan blade. It is also shown that the printed transducers are able to detect acoustic emission events. The ability of the printed transducers to actuate and sense guided wave signals over a range of ultrasonic frequencies is also demonstrated. Furthermore, apart from the noticeable advantages of the non-intrusive nature, and negligible weight as compared to their traditional ceramic counterparts, the printed piezoelectric transducers can potentially be integrated into the manufacturing process in the future, and the presence of transducer arrays ensures the availability of other transducers in case of an individual failure during service. This innovative printing technol-ogy for PZT transducer networks thus holds significant promise in bridging the gap between research advancements and the industrial implementation of SHM technology.