Publications

Laser ablation propulsion and orbit cleaning are developing areas of research. The general aim of laser-based techniques applied to this field is to maximize the momentum transfer produced by a laser shot. This work presents results from ballistic pendulum experiments under vacuum on aluminum, copper, tin, gold, and porous graphite targets. The work has focused on the metrology of the laser experiments to ensure good stability over a wide range of laser parameters (laser intensity ranging from 4 GW/cm2 to 8.7 TW/cm2, pulse duration from 80 ps to 15 ns, and wavelengths of 528 or 1057 nm). The results presented compile data from three experimental campaigns spanning from 2018 to 2021 on two different laser platforms and using different pulse durations, energies, and wavelengths. The study is complemented by the simulation of the momentum from the mono-dimensional Lagrangian code ESTHER. The first part of this work gives a detailed description of the experimental setup used, the ESTHER code, and the treatment of the simulations. The second part focuses on the experimental results. The third part describes the simulation results and provides a comparison with the experimental data. The last part presents possible improvements for future work on the subject.

The use of virtual reality (VR) has made significant advancements, and now it’s widely used across a range of applications. However, consumers’ capacity to fully enjoy VR experiences continues to be limited by a chronic problem known as cybersickness. This issue is caused by the stark discrepancy between the self-motion the vis-ual system perceives through immersive displays and the real motion the vestibular system detects. According to the sensory conflict theory, this mismatch between visual and vestibular cues leads to feelings of sickness and discomfort. This paper presents an initial techniques and framework to reduce the visually induced self-motion in virtual scenes using geometric simplification approaches. The primary goal is to reduce the amount of optic flow experienced by user during the interaction with the virtual environment in a controlled laboratory setup. The proposed framework combines EEG neurofeedback with virtual reality, allowing users’ brain wave activity and cognitive states to be monitored and assessed throughout VR encounters. The empirical evidence amassed from our investigation delineates a significant correlation between the manifestation of cybersickness and en-hanced neural activation within the parietal and temporal lobes. These findings were consistently manifested under two experimental conditions—non simplification and geometrical simplification within the virtual reality (VR) environment. Notably, the observed decrement in activation intensity when employing geometrical simpli-fication substantiates the effectiveness of our VR environment simplification strategy in the attenuation of cy-bersickness.

Effective data reduction techniques are crucial for enhancing computational efficiency in complex industrial processes such as forging. In this study, we investigate various discretization and mesh adaptivity strategies using Proper Orthogonal Decomposition (POD) to optimize data reduction fidelity in forging simulations. We focus particularly on r-adaptivity techniques, which ensure a consistent number of elements throughout the field representation, filling a gap in existing research that predominantly concentrates on h-adaptivity. Our investigation compares isotropic mesh approaches with anisotropic mesh adaptations, including gradient-based, isolines-based, and spring-energy-based methods. Through numerical simulations and analysis, we demonstrate that these anisotropic techniques provide superior fidelity in representing deformation fields compared to isotropic meshes. These improvements are achieved while maintaining a similar level of model reduction efficiency. This enhancement in representation leads to improved data reduction quality, forming the foundation for data-driven models. This research contributes to advancing the understanding of mesh adaptivity approaches and their potential applications in data-driven modeling across various industrial domains.

The functional tolerancing process involves the allocation of the tolerance derived from each functional requirement, expressed at the assembly level, into multiple functional tolerances at the part level. For each part, the manufacturing tolerancing process transfers each functional tolerance into multiple manufacturing tolerances on the dimensions produced throughout the entire process. However, this transfer faces challenges when dealing with tight functional tolerances and constrained process capability. This article proposes an innovative method for adaptively optimizing the production process to enhance its capabilities. Rather than relying on a static manufacturing transfer, this approach involves intermediate measurements of each workpiece during production, modelling its digital shadow. By dynamically adjusting the targets of the upcoming manufacturing dimensions, individual adjustments aim to maximize the likelihood of conformity. This adaptive strategy allows for the allocation of tighter functional tolerances while ensuring workpiece conformity and maintaining the same manufacturing process. Concurrent engineering is thereby facilitated. © 2024 The Authors. Published by Elsevier B.V.

The aim of this article is to extend Moulinec and Suquet (1998)’s FFT-based method for heterogeneous elasticity to non-periodic Dirichlet/Neumann boundary conditions. The method is based on a decomposition of the displacement into a known term verifying the boundary conditions and a fluctuation term, with no contribution on the boundary, and described by appropriate sine–cosine series. A modified auxiliary problem involving a polarization tensor is solved within a Galerkin-based method, using an approximation space spanned by sine–cosine series. The elementary integrals emerging from the weak formulation of the equilibrium are approximated by discrete sine–cosine transforms, which makes the method relying on the numerical complexity of Fourier transforms. The method is finally assessed in several problems including kinematic uniform, static uniform and arbitrary Dirichlet/Neumann boundary conditions.

The solution of a supercritical fluid flowing into a constricted narrow channel is presented in this study. The compressible Navier-Stokes equations in the lubrication limit coupled with the energy equation and the isothermal and non-isothermal van der Waals fluid and perfect gas have been solved. In order to find the semi-analytical solution of these non-linear coupled equations, homogenization technique in the transverse direction has been applied. Because of the high compressibility and high thermal expansion of supercritical fluids, waviness is observed in the flow and thermal fields near the exit of the channel. This effect is attributed to the channel constriction where the slope is maximum, where a strong coupling between the pressure and density gradients exists. Moreover, the density difference between the exit and inlet of the channel drastically increases when one approaches the critical point, corroborating the data from existing literature. © 2024

Multi-Point Incremental Forming (MPIF) process is a new hybrid process that combines two common manufacturing methods. These are Multipoint Forming (MPF) and Incremental Sheet Forming (ISF) processes. In this study, an experimental set-up, based on a MP reconfigurable die, was designed and manufactured to explore the flexibility of this innovative process and its potentialities to produce complex parts using the same tools. The obtained results have indicated that this novel technique, that doesn’t require costly equipments, is an effective approach to manufacture multitude of parts with different shapes. Moreover, it has been shown that the parts geometrical accuracy as well as thickness distribution are enhanced compared to the conventional ISF process and that the geometrical defects, called ‘dimples’ and caused by the pins’ ends, are significantly reduced and almost eliminated after the insertion of a rubber piece between the reconfigurable die and the blank sheet. On the other hand, the effect of the size and geometry of the rectangular pins on the geometrical accuracy and the dimpling defect has been studied using a finite element analysis.

Because of its excellent properties, such as good corrosion resistance, high specific strength and important ductility, the AA5383 aluminum alloy is largely employed for naval applications. In this work, the mechanical behavior of the AA5383 alloy at elevated temperatures, which is an important aspect for the control of forming operations, is investigated. For this purpose, an experimental campaign, including uniaxial tension, biaxial tension, and shear tests, is performed to cover an important range of temperatures (623∼723 K) and strain rates (10⁻⁴∼10⁻ⁱ s⁻ⁱ). A constitutive model for the description of the high temperature behavior of the AA5383 alloy is then proposed. For the deformation behavior, this model combines a viscoplastic flow rule with the BBC2003 anisotropic yield criterion. Also, the prediction of ductile fracture, which is an important aspect for formability, relies on an extended version of the modified Mohr-Coulomb criterion. The extension allows including the impact of temperature and strain rate on ductile fracture as well as a cut-off value for stress triaxiality. Finally, numerical simulations of the experimental tests are performed to identify the flow rule, yield criterion and fracture criterion parameters by combining different optimization methods. The numerical and experimental results of the different tests are in good agreement, which indicates that the proposed constitutive model is well suited for investigating the impact of process conditions on the formability of the AA5383 alloy at high temperatures.

This paper focuses on the impact of cryogenic assistance on the drilling of Ti6Al4V titanium alloy. It develops a relation between the phenomenon of hole shrinkage and measurements performed either during or after the machining operation. Indeed, because this phenomenon is apparently strongly associated with heat generation, which is the main issue in titanium alloy drilling, this work proposes to verify the effect of liquid nitrogen cooling on hole shrinkage, quantify it, and then relate it to these measurements. Specifically, the cutting forces and final hole geometry are analyzed and their variations are explained using the collected data on hole shrinkage.

Drilling operation with cryogenic assistance is beneficial toward solving critical issues in machining difficult-to-cut materials and structures, especially in terms of improving surface integrity, elongating tool life, sustainability, and so on for providing high-performance components in aerospace industries. This article presents an overview of the state of the art on this technique in recent years. It aims at analyzing its requirements and orient future directions. It starts with a summary concerning its application for different categories of work materials, including metals, composites, and hybrid stacks. Then, the main methodologies of numerical modeling and experimental characterization toward understanding the fundamentals are reviewed. The goal is to present a general view of current approaches, discuss their advantages, and disadvantages to understand the requirements toward future work. In addition, impacts of cryogenic drilling on cutting performance are reviewed in terms of thermomechanical loadings, surface integrity, tool wear, and sustainability. Finally, a brief summary is presented from different perspectives, and an outlook is recommended for future orientations.