Publications

This article aims at mapping the current knowledge related to DED-WAAM in order to assess and control the deposition trajectory and associated manufacturing strategy, especially the toolpath, for building weld beads with DED-WAAM technology. To do so, a thorough state of knowledge study from a group of experts and a targeted list of scientific articles points out several issues identified as critical parameters or handles due to their influence onto the deposition trajectory throughout the WAAM manufacturing process, and therefore onto the final part quality. For instance, the studied elements in this work are namely the trajectory generation variables (e.g. deposition rate, fixtures or substrate geometry), the heating parameters (e.g. arc power or heating devices), the manufacturing time management, the weld bead shape defects, the workpiece geometry, or the final part quality indicators. Thanks to a global research methodology, the resulting maps represent the interrelations between the WAAM parameters as well as the multi-physical phenomena at stake before, during and after building a weld beadand encompasses various scientific challenges, whether geometrical, mechanical or thermal. Therefore, they contribute to understanding the main performance criteria for assessing a deposition trajectory, guiding WAAM practitioners' decisions before building a complete part with this additive technology.

The aim of this work is to develop FFT-based solvers for transient diffusion in heterogeneous materials subjected to non-periodic (Dirichlet/Neumann) boundary conditions. We focus on a problem of thermal conductivity and derive a theta-method which includes an implicit solver for transient thermal conductivity in heterogeneous materials. The method is based on a fixed-point iterative solution of an auxiliary problem obtained by a Galerkin discretization using an approximation space based on mixed sine–cosine series. The solution field is decomposed as a known term verifying the boundary conditions and a fluctuation (unknown) term described by appropriate sine–cosine series. The solution of the auxiliary problem involves discrete sine–cosine transforms, of type I and III, which makes the solver rely on the computational complexity of fast Fourier transforms. The method is applied to the prediction of transient thermal fields in a composite material subjected to non periodic boundary conditions.

The aim of this paper is to predict the fatigue behavior of bonded joints made of a bi-component structural acrylic adhesive. The approach considered is based on a characterization of the fatigue properties of the bulk adhesive combined with a finite element modeling of the bonded joint to provide the heterogeneous stress field within the adhesive. The identification of the fatigue model is conducted with experimental bulk adhesive tests under two loadings (tensile–compression and tensile–tensile) in order to account for the effect of the mean stress. A modified Crossland criterion, in the limited life time domain, is used to predict the fatigue life of the bonded joint assembly. The numerical fatigue life determined with this approach is compared to the experimental fatigue life of the assembly. A good correlation is found between the numerical model and the experimental results.

The computation of guided modes in fluid-loaded multilayer plates is generally done by a spatial approach, i.e. solutions are sought for a complex slowness. An alternative approach, less frequently employed, involves seeking solutions for complex frequencies. These frequencies correspond to plate resonances. They denote transient phenomena and the guided modes exhibit non-harmonic behavior. Consequently, conventional methods of averaging over time periods become unsuitable for calculating the means of energy quantities. In other words, the calculation of average fields cannot be reduced to a single average over a time period. To tackle this issue, for a predetermined mode, the average fields are obtained through a single averaging process applied to an arbitrary phase term. This averaging process renders independent the means of all energy quantities from the arbitrary origin phase. As usual, an additional integration across the thickness is conducted to derive total energy quantities. Doing this, the total average fields depend on both time and position on the surface plate. A set of four equations is derived from instantaneous and local energy balance equations. From these averages, the energy velocity can be directly calculated. The equations provide further insights into wave dispersion and damping along the energy flow direction, arising from viscoelastic losses and leakages in fluid.

Capillary-driven flow is a critical phenomenon in fibrous porous media, influencing a wide range of industrial processes such as filtration, drying, and biomass conversion. Understanding the interplay between material properties and fluid behavior is essential for optimizing these processes. This study aims to analyze capillary flow behavior in cotton fibers by combining numerical simulations with experimental data. An inverse analysis approach was employed to determine several unknown parameters associated with three different liquids: n- heptane, water, and glycerol. Based on simulation data, the wicking velocity of each liquid in the porous medium was calculated, followed by the determination of the corresponding capillary numbers (𝐶𝑎). The results indicate that the capillary numbers for n-heptane, water, and glycerol are 4.91 × 10−5, 1.61 × 10−5, and 1.42 × 10−4, respectively, highlighting the differences in infiltration behavior among these fluids. Subsequent simulations systematically examined the effects of porosity, surface tension, and dynamic contact angle on liquid transport. The capillary number was used as a quantitative measure to assess the influence of these parameters on infiltration behavior. Lower 𝐶𝑎 values were generally associated with faster liquid absorption, particularly in cases with higher surface tension and smaller contact angles, where capillary forces dominated

This study compares the experimental and simulated behaviour of solid–liquid expression using a nonlinear predictive model. The model is based on power-law constitutive equations for the local filter cake parameters (permeability, specific resistance, compressibility modulus, and consolidation coefficient), and describes the compressive pressure distributions and consolidation ratio under different pressures. Experimental data from kaolin and bentonite suspensions are compared to model simulations. The experiments involve the formation of semi-solid and pre-compressed by filtration cakes, which are then subjected to solid–liquid expression. The study highlights the influence of initial cake structure on consolidation behaviour and evaluates the applicability of conventional filtration-consolidation theory to non-uniform cakes formed by filtration. The results demonstrate that the predictive model generally aligns with the experimental data, although deviations may occur due to unmodeled effects and experimental inaccuracies.

Aims Overall sagittal flexion is restricted in patients who have undergone both lumbar fusion and total hip arthroplasty (THA). However, it is not evident to what extent this movement is restricted in these patients and how this influences quality of life (QoL). The purpose of this study was to determine the extent to which hip-lumbar mobility is decreased in these patients, and how this affects their QoL score. Methods Patients who underwent primary THA at our hospital between January 2010 and March 2021 were considered (n = 976). Among them, 44 patients who underwent lumbar fusion were included as cases, and 44 THA patients without lumbar disease matched by age, sex, and BMI as Control T. Among those who underwent lumbar fusion, 44 patients without hip abnormalities matched by age, sex, and BMI to the cases were considered as Control F. Outcome and spinopelvic parameters were measured radiologically in extension and flexed-seated positions. Hip, lumbar, and hip-lumbar mobility were calculated as parameter changes between positions. Results There were 20 male and 112 female patients in the case and control groups, with a mean age of 77 years (5 to 94) and a mean BMI of 24 kg/m2 (15 to 34). QoL score and hip-lumbar mobility were reduced in cases compared to Control T and F, and were further reduced as the number of fused levels increased. Hip-lumbar mobility was associated with reduction in activity-related QoL, mostly for those activities requiring sagittal flexion. Conclusion This study confirmed that hip-lumbar mobility is a factor that influences activity, most of all those requiring overall sagittal flexion. Clinicians should focus on hip-lumbar mobility and counteract disability by suggesting appropriate assistive devices.

In recent years, markerless optical systems for biomechanical movement analysis in sports, gait and balance assessments are being used as an alternative to conventional marker based measuring systems. This study compares the performance of the Zed 2i stereoscopic camera against a VICON system in a standing position under three conditions: quiet standing and two movements simulating disturbances in two directions, anteroposterior and mediolateral. This study originates from a collaborative project with a medical team that aims to objectively evaluate balance function in patients recovering from stroke. The displacement and velocities of the centre of mass were calculated and compared in two directions, x and y. A Bland–Altman analysis for non-parametric data, along with the coefficient of determination and mean square error, were used for statistical evaluation. The results demonstrate that the limits of agreement in both sway tasks were greater than those observed in static conditions. However, the coefficient of determination of the sway tasks indicates a significant degree of agreement between the two systems. In contrast, in the static condition, it appears that noise may have a greater influence on the signal than the centre of mass estimate, due to the limitation of the depth algorithm used to estimate the joint positions.

.Previous studies have demonstrated the acceleration signal presents a typical running signature, which allows for the extraction of reliable information. However, few studies have focused on the exhaustion-induced variability of the acceleration signature during running. The present study included 10 participants who ran at a constant speed on a treadmill until exhaustion. The participants were equipped with three accelerometers, located at the lumbar spine, tibia, and foot. The results showed that all the participants kept a constant pace throughout the test (coefficient of variation <5%). Similarities between acceleration signatures were observed using the coefficient of multiple correlation. For the longitudinal axis of the lumbar spine, the longitudinal axis of the tibia, and the anteroposterior axis of the tibia, running signatures were not affected by exhaustion (coefficient of multiple correlation >0.8). For all the other axes, the signature was impacted within and between the states of exhaustion. Signatures were particularly different for the foot sensors, which makes it difficult to use to extract reliable information. The results showed that the coefficient of multiple correlation allowed the quantification of the variability of the running signature, and that each axis and measuring point varied in how they were influenced by exhaustion.

The accurate measurement of spatiotemporal parameters, such as step length and step frequency, is crucial for analyzing running and sprinting performance. Traditional methods like video analysis and force platforms are either time consuming or limited in scope, prompting the need for more efficient technologies. This study evaluates the effectiveness of a commercial Global Positioning System (GPS) unit integrated with an Inertial Measurement Unit (IMU) in capturing these parameters during sprints at varying velocities. Five experienced male runners performed six 40 m sprints at three velocity conditions (S: Slow, M: Medium, F: Fast) while equipped with a GPS-IMU system and an optical system as the gold standard reference. A total of 398 steps were analyzed for this study. Step frequency, step length and step velocity were extracted and compared using statistical methods, including the coefficient of determination (r2) and root mean square error (RMSE). Results indicated a very large agreement between the embedded system and the reference system, for the step frequency (r2 = 0.92, RMSE = 0.14 Hz), for the step length (r2 = 0.91, RMSE = 0.07 m) and the step velocity (r2 = 0.99, RMSE = 0.17 m/s). The GPS-IMU system accurately measured spatiotemporal parameters across different running velocities, demonstrating low relative errors and high precision. This study demonstrates that GPS-IMU systems can provide comprehensive spatiotemporal data, making them valuable for both training and competition. The integration of these technologies offers practical benefits, helping coaches better understand and enhance running performance. Future improvements in sample rate acquisition GPS-IMU technology could further increase measurement accuracy and expand its application in elite sports.