Publications

This study models the evolution of the French electric vehicles fleet depending on different parameters, such as production or recycling capacities, average lithium amount per vehicle, using system dynamics. Following the European Union's 2023 decision to ban internal combustion engine vehicles by 2035, France has focused on securing critical raw materials, including lithium, to support its electrification goals. The system dynamics model incorporates the target growth of the French electric vehicles fleet, lithium extraction from a newly established mine, and recycling rates mandated by European regulations. The results show that reaching the 2050 target is not the only issue: maintaining the fleet at a stable state is not evident if the three parameters mentioned above are not balanced. This study concludes that the European Union’s legal targets are not enough to ensure the perennity of the electric vehicles fleet.

In the context of the Industry 4.0, new processes have appeared, such as the additive manufacturing (AM) process. Therefore, new approaches to de-sign parts have to be developed to integrate process constraints. It is very difficult for teachers to effectively guide students during conceptual design for AM, even though various idea generation techniques and methods are available. AM re-quires an important preparation and compromise in design phases. In addition, design need to be generated in a digital environment. Among the various steps, critical impacts on the final part quality are linked to part orientation. So, this paper focuses on the conceptual design phase to educate future technician and engineers to the design for additive manufacturing. Pilot-study on the teacher's role interacts through active pedagogical tool with students. They need to think in 3D and create directly in 3D. The propose education development use an im-mersive tool to consider the process constraints. Thereby, students need to deal with an AM process chain. New approaches are analyzed based on the design guidelines for Additive Manufacturing, which were developed by the students themselves. Also, the students estimated opportunities and limits linked to prod-uct-process relationship. Finally, the success of the new course contents and form is reviewed by a student evaluation.

Opportunities are offered by multiple Additive Manufacturing (AM) processes nowadays. Design rules are evolving to lead to lighter and stiffer parts with really more complex shapes than those obtained by conventional processes. Worldwide, new methodologies/tools of assistance for the design are developed such as Design for Additive Manufacturing (DfAM). Additive manufacturing can allow the development of new metamaterials and health-matter evaluation based on energy flow evaluation. In this paper, the objective is to generate a new methodology with DfAM based on mesoscale knowledge. It is generated with open lab bench and simple object characterization. A methodology is presented to formalize and quantify information at multilayer dimension. A database is also generated following Design of Experiments (DoE) to obtain metamodels. They are developed for specific features representative of AM geometric class such as overhanging, holes or walls for instance. Mereotopological primitives with their AM definitions are used to define features in term of space and time variables. This theory enables the formalization of knowledge at the mesoscopic scale taken into consideration layer by layer build-up. It is then possible to use it to integrate data and information to the different feature juxtapositions using recognition algorithm. Information for each feature can then be included and explicitly used to help the designer during detailed design phase. A global 4-steps DfAM methodology maximizing the potential of AM is presented and validated through a part from the space industry use case. It includes the definition of skeleton/skin entities, pattern decomposition, information associated based on material evaluation and decision for AM part.

AbstractAdditive manufacturing (AM) processes are now integrated in industry. Therefore, new methods to design AM parts taken into consideration capabilities and limitations are necessary. It is very difficult for teachers to effectively guide students with ideas emerging from generative design tools. AM requires significant preparation and compromises. Topological optimization is also used depending on requirements. A significant impact on the final part quality is related to the part orientation and geometric dimensions. Therefore, this white paper focuses on detailed design steps to prepare future technicians and engineers to design for additive manufacturing. Active teaching pedagogy guideline is proposed. Students have to think in 3D and use analysis tools to create and validate the optimised design. They use immersive tools to review constraints and model diagnostic algorithm to generate data. Present approaches with design guidelines and tools enable to create AM rules based on it. Questionnaire shows that students need explicit knowledge information. Features recognition and geometry diagnostic are mandatory for complex model. Immersive tool helps to evaluate post-processing. They can now relate AM product-process relationship.

The paper investigates the influence of adaptive sampling strategies on the generation of a metamodel based on Non-Uniform Rational Basis Spline (NURBS) entities, obtained from unstructured data, with the purpose of improving accuracy while minimising computational resources. The metamodel is defined as solution of a constrained non-linear programming problem and it is solved through a three-step optimisation process based on a gradient-based algorithm. Moreover, this paper introduces a generalised formulation of the NURBS-based metamodel capable of handling unstructured sampling data, enabling simultaneous optimisation of control points and weights. Sensitivity analyses are performed to evaluate the influence of various adaptive sampling techniques, including cross-validation-based and geometry-based strategies, on the resulting metamodel, in terms of accuracy and computational costs. Analytical benchmarks functions and a complex real-world engineering problem (dealing with the non-linear thermomechanical analysis of a part produced with the fused deposition modelling technology) are used to prove the effectiveness of the NURBS-based metamodel coupled with adaptive sampling strategies in achieving high accuracy and efficiency. © 2025 Elsevier B.V.

When performing upscaling of transport phenomena in multiscale systems it is not uncommon that terms of different physical nature than those present at the underlying scale arise in the resulting averaged differential equations. For diffusive species mass transfer with heterogeneous reaction and conductive heat transfer, additional terms result from upscaling using the volume averaging method, which are classically discarded by means of orders of magnitude estimates. In this work, these two cases are revisited and it is shown that, for single and two-species diffusive mass transfer with heterogeneous nonlinear reaction, the additional term is exactly zero using Green's formula. This conclusion is shown to also be applicable when using the periodic homogenization method. Nevertheless, for heat conduction, with and without considering interfacial resistance, only the dominant conduction-corrective terms are shown to be zero also using Green's formula. In contrast, the contribution of the co-conduction-corrective terms may be relevant depending on the systems characteristics, the properties of the phases and the macroscopic boundary conditions. This is exemplified by performing numerical simulations in a non-symmetric unit cell. © 2025 Elsevier Ltd

In some laser assemblies, optical components are glued on their metal mount using a photocrosslinkable adhesive. All these components are submitted to medium to high temperatures for several hours upon laser's operation time. The subsequent thermal stresses endured by the adhesive could lead to its degradation, alter thus the functioning of the assembly and impact the alignment of the laser, key issues in laser applications. This work focuses on the investigation and the modeling of the lifespan, the degradation in the face of thermal stresses, particularly those generated by a laser, and of the ageing of a photocrosslinkable adhesive, PC373HA. The thermal characterization is performed using ThermoGravimetric Analysis and allows for the development, the validation and the comparison of three models based on Arrhenius' law to estimate the lifetime of adhesives as a function of temperature. A temperature of 150 °C is identified as a threshold to ensure limited degradation over the 15 h requested for laser operation endurances. The Ozawa-Flynn-Wall model and the Kissinger-Akahira-Sunose model correctly reproduce PC373HA's thermal behavior submitted to different thermal scenarii (temperatures, heating rates …). Both show that the higher the temperature, the faster the degradation process, approximately 10 min at 220 °C and 100 min at 180 °C, much less than the required 15 h. Besides, in the event of an incident with the laser, if the temperature exceeds 200 °C for more than 10 min or 180 °C for more than 100 min, corrective action should be taken, and the adhesive should be replaced. These models therefore provide fundamental information for laser applications and will allow the implementation of preventive solutions during use but also in case of incident. © 2025 Elsevier Ltd

The upscaling process of coupled (single- and two-species) diffusion with heterogeneous chemical reaction in homogeneous porous media is revisited in this work with several important clarifications following the article from Bourbatache et al. (Acta Mech 234: 2293-2314, 2023. https://doi.org/10.1007/s00707-023-03501-w). It is shown that the upscaled model obtained from the volume averaging method (VAM) or, equivalently, following an adjoint and Green’s formulation technique provides a closed model without any a priori assumption on the form of the solution for the pore-scale concentration involved in the spectral approach used in the periodic homogenization method (PHM) reported in the above reference. Through comparison with direct pore-scale simulations, the VAM model is shown to outperform the predictions of the average concentration and average flux profiles for the simple two-dimensional configuration considered in Bourbatache et al. (Acta Mech 234: 2293-2314, 2023. https://doi.org/10.1007/s00707-023-03501-w) in comparison with the model obtained from PHM in this reference. Finally, identification of the apparent effective diffusion coefficient from these pore-scale simulations, which serve as in silico experiments, proves that the correct dependence upon the Damkhöler number is the one predicted by the model obtained with VAM, in contradiction with the conclusion put forth in Bourbatache et al. (Acta Mech 234: 2293-2314, 2023. https://doi.org/10.1007/s00707-023-03501-w). The physical explanation lies in the corrective contribution of the reactive part to the apparent effective diffusion coefficient, which is positive and adds up to the pure intrinsic diffusive part. The discrepancy between PHM and VAM approaches is proved to originate from the choice of changes of variables in the pore-scale concentration used in the spectral approach while employing PHM. © The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature 2025.

This paper presents an experimental and numerical analysis of heat transfer and thermal deformation in small-dimension (1.4 mm) liquid mechanical seals operating in an unstable dynamic tracking mode. The studied non-contacting mechanical seal is used in a liquid pump for turbojets. The study aims to estimate the values of pressure, temperature, and thermal deformations that can prevent excessive wear of the sealing rings and control the increase in leakage rate or power loss during operation. Experimental investigations were conducted under a nominal inner pressure of 0.7 MPa, across a wide range of rotational speeds (from 1000 to 6000 rpm), and at low Reynolds numbers (Re < 70). Two high-viscosity fluids, glycerol and engine oil, were used as sealing fluids. Rotational speeds and inner pressure were set as boundary conditions in the simulations. Temperatures measured by thermocouples during the experiments were used to compare with the simulation results. Simulations were performed using the computational fluid dynamics (CFD) software COMSOL. The two-dimensional numerical models accounted for thermal transfers and face seal deformations, coupled with the pressure field in the lubrication fluid. The effects of various sealing fluids and rotational speeds on the time-dependent behavior of temperature, displacement, and pressure within the thin liquid lubricant film were investigated. Subsequent comparisons between experimental and numerical results, particularly for temperature data measured by thermocouples under various operating conditions, demonstrated strong consistency. The greatest discrepancy observed was less than 1.2 °C. © 2025 The Authors

Over the past few years, femtosecond (fs) laser processing has drawn a growing interest in a wide range of applications as it offers the possibility to process the surface morphologies of metals and semiconductors. In contrast to other polishing techniques, laser polishing offers a flexible and non-contact solution, thereby avoiding potential external contamination, while enabling a precise selection of processing areas. We investigated the influence of fs laser parameters on surface roughness of pure copper and ablation thickness, focusing on highlighting the importance of fluence and scanning overlap. With a two-step processing strategy, composed of coarse and fine polishing steps, surfaces with Sa < 400 nm were achieved, representing a 98% reduction from the high roughness of 15 μm on initial surfaces. This research demonstrated the possibility of directly polishing rough parts using a fs laser with a perpendicular incidence. © 2025