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Machine learning-based analytical approach for mechanical analysis of composite hydrogen storage tanks under internal pressure
No full textInternational audienceThis study is a practical exploration of the application of machine learning for the mechanical analysis of filament-wound thin-composite hydrogen storage tanks under internal pressure. Our innovative approach seamlessly integrates classical laminate theory, comprehensive parametric analysis, and machine learning to advance the state-of-the-art in composite tank design. This versatile framework holds promise for addressing challenges in other structurally complex systems. A comprehensive parametric study was then conducted to explore the influence of key design parameters, such as internal pressure, tank radius, order of layer, and layer orientation. Pearson's correlation analysis was used to determine the parameters that had the most significant impact on the mechanical behavior of the tank. In addition, five machine learning models, namely, Extreme Gradient Boosting, Adaptive Boosting, Artificial Neural Network, Support Vector Machine, and Random Forest, were examined to determine their predictive capability for the mechanical performance of these composite tanks. Key findings demonstrate XGBoost's superior predictive capabilities, achieving a remarkable 99% accuracy in predicting stress in the x-direction compared to Random Forest's 96%. XGBoost also outperformed Random Forest in terms of Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE) with values of 26 and 0.02, respectively, versus 207 and 0.16. These results underscore XGBoost's potential to revolutionize hydrogen storage tank design. The development of a user-friendly GUI application further enhances the practicality of this research, allowing engineers and composite designers to efficiently simulate the mechanical behavior of these tanks in real time by adjusting the cursors for variables such as the pressure, radius, layer order, and layer orientation. This tool, with its intuitive interface and elimination of manual calculations, promises significant enhancements in the design process, providing a platform for the rapid assessment and optimization of tank architectures, thereby improving the efficiency and reliability of the design process
Combining XRD and nanoindentation to characterize mechanical properties evolution of flax cell walls during controlled heat treatment
No full textInternational audienceOver the past decades, a tremendous interest has been developed concerning plant fibre used to reinforce composite materials as these fibers show comparable mechanical properties and higher ecological benefits than synthetic fibres such as glass fibres. Environmental concerns are currently driving interest in the replacement of thermoset matrices by thermoplastic polymers and pave the way for recycling and composting as end-of-life routes for plant fibre composites. However, using thermoplastic polymers as a matrix involves long processing cycles at high temperature, which may negatively affect both structure and mechanical properties of plant fibres. In this work, structural evolution and mechanical behaviour of flax fibre cell walls were dynamically monitored in-situ by X-ray diffraction and nanoindentation from ambient to 230°C. A drop in local mechanical performance of flax cell walls, associated with structural evolution at different scales and changesin the biochemical composition, were noticed while increasing temperature. This work, proposing for the first time an in-situ investigation of the dynamic evolution in temperature of the flax cell wall properties, also highlighted the reversible behaviour of their crystalline structure and local mechanical properties, after cooling to room temperatur
Développement d’une source attoseconde intense basée sur des miroirs plasma relativistes à haute cadence
No full textThe experimental work presented in this manuscript was carried out at Laboratoire d’Optique Appliquée (LOA, Palaiseau, France) on a compact kHz multi-mJ energy laser system capable of delivering waveform-controlled near-single-cycle pulses. The first part of this work is focused on improving the performance of this laser source by integrating a cryogenically-cooled multi-pass amplifier in the laser chain in order to increase the output energy, enhance the laser waveform stability, making the laser source more stable and reliable, and with more overall reproducible day-to-day performance. Furthermore, we explore laser post-compression and temporal contrast enhancement in a multipass cells. In the future, this post-compression scheme when power-scaled and integrated into the laser chain will further enhance the focused pulse intensity for experiments.The second part of this work focuses on using the laser system to drive relativistic plasma mirrors on the surface of initially-solid targets to generate highly energetic particle beams (ions and electrons) and harmonic radiation in the extreme ultraviolet region, corresponding to attosecond pulses (1 as = 10^{-18} s) in the time domain. We could produce relativistic electron beams by localized injection of electrons into the nonlinearly reflected laser field by the plasma mirror. Additionally, we could generate nearly-collimated MeV-class proton beams in a controlled pump-probe experiment. By stabilizing the waveform of the driving laser pulses, we could temporally gate the interaction process on the target surface and produce isolated attosecond pulses. We performed a comprehensive parameter study to fully characterize and optimize the spatio-spectral properties of the emitted XUV attosecond pulses, laying the groundwork for their refocusing for applications.Le travail expérimental présenté dans ce manuscrit a été réalisé au Laboratoire d'Optique Appliquée (LOA, Palaiseau, France) sur un système laser compact multi-mJ kHz, capable de délivrer des impulsions quasi-mono-cycle à phase enveloppe-porteuse (CEP) stabilisée. Le premier volet expérimental a consisté à améliorer les performances de la source laser grâce à l’intégration d'un étage d’amplification multi-passage cryogéné dans la chaîne destiné à augmenter l'énergie d'impulsion disponible, à améliorer la stabilité de la CEP, ainsi qu’à fiabiliser les performances quotidiennes du laser. En parallèle, une nouvelle technique a été testée, basée sur la propagation nonlinéaire dans une cellule multi-passage (MPC), afin de post-comprimer temporellement et d’améliorer le contraste temporel des impulsions laser. Dans l’avenir, une fois mis à l’échelle et intégré dans la chaîne laser, ce dispositif innovant de mise en forme temporelle d’impulsions laser, augmenter encore plus l’éclairement atteignable pour les expériences.Le deuxième volet expérimental est axé sur l'utilisation de la chaîne laser afin de piloter des miroirs plasma relativistes et de générer du rayonnement attoseconde (1 as = 10-18 s) dans le domaine spectral de l’ultraviolet extrême, ainsi que des faisceaux d’électrons et d’ions fortement énergétiques. Nous avons pu produire des faisceaux d'électrons relativistes par injection localisée d’électrons du plasma dans le champ laser réfléchi de manière nonlinéaire par le miroir plasma. En outre, nous avons pu générer des faisceaux quasi-collimatés de protons avec des énergies proches du MeV dans le cadre d’une expérience pompe-sonde contrôlée. En stabilisant la forme d'onde des impulsions laser, nous avons pu restreindre temporellement le processus de génération d’harmoniques en-dessous du cycle laser et ainsi produire des impulsions attoseconde uniques. Nous avons réalisé une étude paramétrique complète afin d'optimiser les propriétés spatio-temporelles des impulsions attosecondes XUV ainsi émises, jetant ainsi les bases de leur refocalisation pour les applications
The SFIR Test: An Innovative Hydrostatic Compression Test to Characterize the Volumetric Behavior of Polymeric Foams
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On the Relationship Between the Vogler Algorithm Derivation and the Parabolic Equation for Multiple Knife-Edge Diffraction
No full textInternational audienceWe prove the equivalence between the derivation of the Vogler algorithm and the parabolic equation for multiple knife-edge diffraction problems under certain conditions. To illustrate the key ideas, we present two case studies for single and double knife-edge diffraction, where the proposed results generalize the available results in the literature. The insight from our proof can serve two purposes: allowing cross-checking results of the Vogler algorithm and the parabolic equation; and building the foundation on which new methods for solving this essential problem and related ones can be developed
Long-range electromagnetic propagation above a polluted sea surface: hybrid modeling
No full textInternational audienceModeling electromagnetic propagation in the maritime environment is a key element in calibrating detection tools, for example in SAR imaging. This article presents a method to compute the propagation above a polluted sea surface. The latter is based on the parabolic wave equation solved with the split-step wavelet method. A hybrid method is also used to account for the sea surface. Indeed, here the sea spectrum is used to both generate random sea surfaces and compute a roughness parameter. The contributions of this article are twofold. First, we improve the calculation of the roughness coefficient in the hybrid method by accounting for the shadowing effect. Second, a stochastic strategy is developed to account for an insoluble oil slick, or pollutant, that covers part of the domain. Numerical tests in the S-band are provided to validate the method and highlight its advantages
On the determination of the primary part of the seismically induced inertial forces in pressurized piping systems
No full textInternational audienceThis paper focusses on discussing which part of inertial stresses should be regarded as primary or secondary. To do so, a classification is established based on the study of non-linear oscillator. The case of zero and non-zero-permanent force are explored to simulate the pressure effect. Two types of dynamic signals are considered as samples of a wide-band and a narrow-band stochastic process to simulate ground level motions and floor input motions respectively. The results of the classification highlight the importance the φ parameter, the ratio between the natural frequency of the oscillator and the central frequency of the input motion, in the calculation of the primary part of the inertial forces. Based on the defined classification, a reduced spectrum method, initially proposed by Labbé and Nugyen [Modified Response Spectrum Accounting for Seismic Load Categorization as Primary or Secondary in Multi-Modal Piping Systems, ASME 2021, PVP] is tested numerically on a piping system. Non-linear calculations are compared to the results of the linear reduced spectrum analysis. Von-mises stresses at the most damaged elbow flank and opening/closing displacement of the same elbow are compared. Comparable results are obtained in term of stresses
The Question Concerning Technology in a Rocket Age in China and the West
No full textInternational audienceThis essay, a talk given on two occasions in the spring of 2024, explores the political and cultural implications of space expansionism, and in particular the notion of astrocolonialism, with respect to existing normative ideas concerning political order in China and the Western tradition. It engages with the work of Martin Heidegger as well as the contemporary Chinese philosopher Tingyang Zhao. It is arguably a contribution to the study of what Yuk Hui calls "Cosmotechnics," and more specifically a study of the implications of space expansionism for the discursive orientation of tradition ways of imagining the spatial relationship between technology and the cosmos.
