Laboratoire de Mécanique et Procédés de Fabrication

The present study evaluated the nutritional status of industrial sugarcane (Saccharum officinarum L.) plantations managed by SOSUMO in Burundi using the Compositional Nutrient Diagnosis (CND) method via the CNDr² index. Foliar samples from 41 plots were analysed for seven key nutrients: Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Copper (Cu) and Zinc (Zn). A CNDr² threshold of 7.4 was established to identify significant nutritional imbalances. Results showed that 56.1% of plots had low yields linked to nutrient deficiencies, mainly Magnesium (27%), Nitrogen (17%), and Potassium (15%). Zinc and Copper deficiencies affected 12–14% of plots. About 22% of plots had low yields despite balanced nutrition, highlighting non-nutritional factors such as soil or management issues. Conversely, 9.8% of plots achieved high yields despite imbalances, suggesting short-term compensation through intensive practices. The CNDr² index proved a reliable tool for diagnosing nutrient imbalances and guiding fertilisation strategies aligned with the 4R nutrient stewardship principles. The study underscores the importance of adapting nutrient recommendations to local soil, climate, and crop conditions while addressing non-nutritional constraints to sustain and improve sugarcane productivity in Burundi.

Using laser-based powder bed fusion (LB-PBF) to process H13 steel holds significant promise for fabricating advanced molds for applications in the automotive industry. In this study, a novel strategy involving elevated preheating temperatures was employed to enhance the fatigue properties of LB-PBF H13 steel, particularly in the as-built condition. Fatigue tests were conducted on specimens fabricated at 200°C and 500°C preheating temperatures, with non-destructive characterization techniques, including μ-CT, white light interferometry (WLI), and X-ray diffraction (XRD), employed to analyze surface roughness and residual stress. The results indicate that preheating at 500°C significantly enhances the fatigue performance compared with that at 200°C, particularly in the high-cycle regime for the as-built samples, despite a modest increase in surface roughness at 500°C. The improved fatigue life, ranging from 2 to 73 times greater, can be attributed primarily to the substantial reduction in residual stresses (from 487 MPa to 64 MPa). This reduction minimizes both the number and size of critical crack-initiating surface defects. Quantitative rationalization via Kitagawa-Takahashi (K-T) diagrams indicates a transition in fracture mechanisms, from multiple-surface crack initiation in the 200°C samples to single-surface initiation in the 500°C samples, due to reduced stress concentrations and modified crack propagation behavior. This study underscores the critical role of residual stress control over surface roughness in enhancing the fatigue performance of LB-PBF H13 steel, offering valuable novel insights for optimizing process parameters in the production of high-performance molds.

This paper deals with a combined experimental/numerical approach to identify the degradation profile of the magnetic properties at the cutting edge of mechanically cut electrical steels. Using a dedicated magnetic measurement device combined with a specific magnetic characterization protocol and mechanical hardness measurements, the impacted distance to the cutting-edge (I.C-E) of a non-oriented (NO) Si-Fe electrical steel has been experimentally delineated. Then, thanks to a magneto-plastic model together with a Finite Element (FE) method-based numerical model, the I.C-E distance and the associated degradation profile have been determined by an inverse optimization method. The obtained results show that the degradation profile, although it follows a classical rapid decrease from the cutting edge, is quite different from those usually considered in the literature.

Abstract The formability of thin sheets governs the feasibility of plastic deformation and shaping processes. Consequently, the identification of the laws of behaviour and its damage mechanisms proved to be necessary to master and validate the operating modes of the processes of obtaining the finished stampings. This is established using the standardized Erichsen test, whose responses in Erichsen index and division of constraints coupled with local aspects of damage allow decision-making to be established in order to arrive at a strategy of productivity and quality shaping. The present work deals with these aspects for the case of Fe-Zn coated thin sheets deposited on a grade of Duals-Phases steels (DP600) in order to take them into account via the identification of the models of the damageable behaviour required according to the formulation of the Gurson-Tvergaard-Needleman (GTN) law. To do this, experiment plans combined with EF simulation have been adopted according to the concepts of Response Surfaces Methodology (RSM). As a result, taking into account the presence of Fe-Zn coating will optimize the stamping processes on an industrial scale without causing its decohesion during shaping by plastic deformation.KeywordsDP600GTN damage modelErichsen test

IMéRA – Marseille (Idemec, A*Midex Aix-Marseille Univ.) Le workshop international « Connectivités djerbiennes : Globalisations méditerranéennes des Juifs de Djerba » que nous avons co-organisé, initialement prévu en mars 2020 à l’IMéRA à Marseille, s’est finalement tenu en présentiel les 27 et 28 juin 2022. Son objectif était d’inaugurer une recherche collective et pluridisciplinaire menée dans le cadre d’un programme financé par l’A*Midex (Aix-Marseille univ.) en partenariat avec le Centre d...

ABSTRACT Carbon fiber-reinforced polymer composites have been mainly used for several applications owing to their thermo-mechanical properties. Fused deposition modeling is a rapidly growing additive manufacturing technology owing to its ability to create a functional part with complex geometries. The tensile properties of polyamide-6 and carbon fiber-reinforced polyamide (PA6/CF) composite parts were compared. The influence of printing parameters as feed rate, build orientations, and layer thickness on the tensile characteristics of the printed parts were studied. The tensile properties of the fabricated materials were investigated at the piece scale considered as macroscopic scale and at the filament scale considered as mesoscopic scale. Scanning electron micrography of the fracture surfaces of the specimens revealed the origin of rupture at the microscopic scale. The density of the printed specimens was also compared to correlate the process parameters to the microstructure and therefore mechanical properties of the final part.