Publications

In this work, experimental tests and numerical simulations are carried out to investigate the buckling behavior and failure modes of auxetic cellular structures and sandwich panels with auxetic cores. Different Poisson's ratios and densities are considered to evaluate the impact of these parameters on the deformation mechanisms under uniaxial compression loading. The numerical analysis is performed using the Riks method, while considering geometric nonlinearity and elastoplastic behavior. The results indicate that negative Poisson's ratio and structure density have a significant influence on the buckling critical stress and the failure mechanisms of cellular structures. Although the inverted honeycomb and the double arrowhead with different Poisson's ratios exhibit similar load capacity, facesheet failure is more pronounced with the conventional inverted honeycomb. This result can be attributed to the dominant effect of the facesheet on the load evolution. The effects of the cell-wall thickness and the facesheet thickness on the buckling load are also discussed based on the finite element model.

Lifting hydrofoils are gaining importance, since they drastically reduce the wetted surface area of a ship, thus decreasing resistance. To attain efficient hydrofoils, the geometries can be obtained from an automated optimisation process. However, hydrofoil simulations are computationally demanding, since fine meshes are needed to accurately capture the pressure field and the boundary layer on the hydrofoil. Simulation-based optimisation can therefore be very expensive. To speed up the fully automated hydrofoil optimisation procedure, we propose a multi-fidelity framework which takes advantage of both an efficient low-fidelity potential flow solver dedicated to hydrofoils and a high-fidelity RANS solver enhanced with adaptive grid refinement and dedicated foil-aligned overset meshes, to attain high accuracy with a limited computational budget. Both solvers are shown to be reliable for automatic simulation, and remarkable correlation between potential-flow and RANS results is obtained. Two different multi-fidelity frameworks are compared for a realistic hydrofoil: only RANS based and potential-RANS based. According to the optimisation results, the drag is able to be reduced by 17% and 8% in these frameworks, within a realistic time frame. Thus, industrial optimisation of hydrofoils appears possible. Finally, critical areas of future improvement regarding the robustness and efficiency of the optimisation procedure are discussed in this study.

Designing automotive Head-Up Displays (HUD) interfaces requires careful consideration of visual guidelines to ensure safety. While specific safety guidelines exist, a general set of visual guidelines has not yet been established. Therefore, this research presents a comprehensive methodology to derive overall visual guidelines designed to project warnings on HUD interfaces. To this end, the present work focused on asking 20 test subjects for driving in various scenarios, while visual stimuli were projected on a specific HUD system, identifying drivers’ behavior patterns and reaction trends. These visual stimuli were based on already tested visual guidelines. The results obtained from this methodology show that it is possible to integrate all previous qualitative and quantitative visual guidelines, allowing for drivers faster reactions and better recognition of warnings. This integration enables determining the most and the least suitable way for presenting information in a specific HUD system concerning identification mistakes and reaction times. Moreover, these findings imply the feasibility of anticipating a driver’s comprehension of warnings in HUD interfaces.

The study of capillary flows in cellulose fibers is important for various applications, including biomass pyrolysis and drying processes. This work investigates the behavior of cotton fibers during capillary impregnation using a dynamic approach. The analysis utilizes the Washburn equation and tensiometric methods to investigate geometric factors, apparent advancing contact angles, surface free energy of cotton fiber, and capillary pressure. The research is carried out in two phases. The first phase focuses on the theoretical application of the Washburn equation in porous cotton fibers, specifically examining capillary wicking behavior within a cylindrical holder. The second phase involves experimental analysis, using three different liquids: n-heptane, water, and glycerol. The surface tension of the liquids was measured, and the capillary impregnation process was characterized through the determination of geometric factors, apparent advancing contact angles, and surface free energy. The geometrical factors of cotton fibers within the sample holder were found to be 10.39 ± 1.28 mm5. The apparent advancing contact angles for water and glycerol were 74.93◦ ± 2.20◦ and 69.55◦ ± 1.83◦, respectively

The industry sector has long been seeking methods to enhance its manufacturing system control, production, and monitoring, while maintaining the quality of its products and reducing costs and time. One method for achieving a more comprehensive understanding of the manufacturing processes is the identification of a corresponding process window (PW). However, there is no globally accepted definition of process window, which is principally used in different manufacturing processes. In some cases, it is combined with operating window or process map concepts. In light of the aforementioned consideration, this article puts forth a definition of process window, drawing upon the various notions and aspects related to the optimal process parameters selection as discussed in the literature. Furthermore, the identification of key controllable process parameters and the criteria to delimit boundaries of desired parts are described as aspects to identify the corresponding process window. Moreover, this paper provides an overview of the techniques used to establish a process window, principally through the application of machine learning techniques (ML) and design of experiments (DOE). Furthermore, the uncertainty intrinsic to the manufacturing process and the methodologies employed to identify the process window are examined. In conclusion, this article emphasises the necessity of transferring these models to new materials or machines, which will require further investigation in future research.

Risk management has always been a trend in manufacturing related literature in the era of zero-defect manufacturing (ZDM). However, a gap still exists to present a holistic viewpoint of the integration for a product and its related processes involved during decision-making in manufacturing industry. The (knowledge-driven) integrated-decision support system indicates the opportunity by integrating the product design and manufacturing processes related risks in a manufacturing industry to make better decisions at the shop foor. It further proposes a direction towards development of a decision support system framework for their respective risks’ identifcation as well as mitigation to enhance the quality, while minimizing time and cost. Over the years, risk identifcation has been considered well but risk mitigation has mostly been overlooked in the published literature. This paper scanned over a thousand papers from renowned journals published between 2005 and 2024. Currently, the evolu tion involved in the advancement of decision support tools for risk management has been reviewed by utilizing systematic literature review methodology. The study also provides a design overview, highlighting its features, pros, and cons of the existing methods which can be used for risk identifcation, prioritization, and mitigation in the development of a dynamic decision support system to aim (data-driven) zero-defect manufacturing (ZDM). Lastly, the paper discusses the current challenges and opportunities to lessen the manufacturing recalls in the industry, followed by phases of the proposed model.

Ultrasonic fully reversed tension fatigue tests have been performed in the Very High Cycle Fatigue (VHCF) regime (Nr> 1E7 − 1E8 cycles) on Ti-6Al4V specimens containing a controlled internal notch. Two sets of samples have been used. The first one contains a central chimney along the specimen longitudinal axis which brings air to the internal notch; in the second series the notches are not connected to the surface. The microstructure present below the fracture surface of the broken specimens has been studied by electron microscopy (EBSD, TKD and TEM). The formation of nanograins and nanovoids was observed below the surface of the cracks growing in a vacuum environment but not below the surface of cracks connected with ambient air. In the latter case extensive striations were observed. Below each striation the formation of tensile {10-12} twins was observed.

Energetic transition in automotive industry leads to production of new parts such as battery trays. These parts present machining challenges linked to their vibration. It was shown that dynamic model accuracy is highly conditioned by fixture modeling. In the present work a clamping modeling approach for machining simulation is presented. Updating methodology of fixture stiffness and damping, based on dynamic reduction, is detailed. It allows to assess the influence of fixture on part dynamic behaviour in machining. Numerical predictions of ma chined surface geometry are compared to experiments on a battery tray part.

Background Measuring passive hip flexion range of motion (ROM) is challenging due to compensatory movements. Despite the interest in using functional lateral radiographs for assessing hip mobility, the relationship with passive hip flexion ROM remains unclear. This study aims to elucidate this relationship and clarify spinopelvic parameters and mobility factors influencing variations in passive and radiographic hip flexion ROM. Methods A retrospective cross-sectional study was conducted on 154 preoperative patients undergoing primary total hip arthroplasty. Passive and radiographic hip flexion ROM were assessed to clarify these relationships, and these differences were classified into 3 groups (O, A and U). Spinopelvic and hip parameters were assessed in standing, relaxed-seated and flexed-seated positions, as well as lumbar, pelvis, and hip mobility between each position to identify factors influencing differences. Results There was a moderate correlation between passive and radiographic hip flexion ROM (R2 = 0.48, P < .01). A significant difference was found in pelvic and hip alignment in the flexed-seated position between all groups. In postural changes, the O group, which had more patients with relatively low hip mobility, showed greater lumbar spine and pelvic movement, while the U group, which had more patients with relatively high hip mobility, showed less lumbar spine and pelvic movement. Conclusions This study confirmed that passive hip flexion ROM and radiographic hip flexion ROM correlate and that spinopelvic and hip alignment and mobility influence these differences. This result suggests that clinicians should consider lumbar and pelvic alignment and mobility in clinical practice to improve the accuracy of passive hip flexion ROM measurements.

Study Design. Retrospective study of a multicentric prospective database. Objective. This study aimed at describing the relative contribution of vertebral bodies versus discs to lumbar lordosis, and its variation with age and pelvic incidence. Summary of Background Data. While studies sought to determine the physiological magnitude and distribution of lumbar lordosis, data regarding its anatomical composition is lacking. Methods. This study included healthy volunteers with full-body stereoradiographs in free-standing position, without lumbosacral transitional vertebra or age under 18. The following parameters were analyzed: age, sex, pelvic incidence (PI), lumbar lordosis (LL). Posterior heights and sagittal Cobb angles between upper and lower endplate for each lumbar disc and each vertebral body were measured from L1 to S1. Ratios of contribution to LL were calculated for each disc and vertebral body. The cohort was divided into four age groups and four PI groups. Results. 645 subjects were included, mean age was 37.6±16.3, 51% of females. There was a significant decrease in total lumbar disc lordosis with age (−48.9±9.7° to −42.9±10.2°), occurring in lower LL. Vertebral bodies were significantly more kyphotic in Seniors than Youngs (−8.9±8.4° vs. −5.0±9.4°, P=0.03), driven by a significant increase in kyphosis of L1 and L2 bodies. Vertebral body contribution to LL significantly increased between groups as PI increased, from a median of 8.0% to 20.5% (P&lt;0.001). This decrease in disc contribution in favor of vertebral bodies mainly took place in lower LL. Conclusion. This study highlights the importance of vertebral contribution to lumbar lordosis, ranging from 8 to 21% among PI groups. Lumbar lordosis decreased with aging through decreased disc lordosis in the lower lumbar spine and increased body kyphosis in the upper lumbar spine. These results may help surgeons in the assessment of sagittal alignment and the selection of operative technique to achieve surgical correction.