Laboratoire des Systèmes Mécaniques et d'Ingénierie Simultanée

The microstructure in the surface layer of a pure iron plate was refined at the nanometer scale by means of a surface mechanical attrition treatment that generates repetitive severe plastic deformation of the surface layer. The subsequent nitriding kinetics of the treated iron with the nanostructured surface layer were greatly enhanced, so that the nitriding temperature could be as low as 300 degrees C, which is much lower than conventional nitriding temperatures (above 500 degrees C). This enhanced processing method demonstrates the technological significance of nanomaterials in improving traditional processing techniques and provides a new approach for selective surface reactions in solids.

The rapid prototyping has been developed from the 1980s to produce models and prototypes until the technologies evolution today. Nowadays, these technologies have other names such as 3D printing or additive manufacturing, and so forth, but they all have the same origins from rapid prototyping. The design and manufacturing process stood the same until new requirements such as a better integration on production line, a largest series of manufacturing or the reduce weight of products due to heavy costs of machines and materials. The ability to produce complex geometries allows proposing of design and manufacturing solutions in the industrial field in order to be ever more effective. The additive manufacturing (AM) technology develops rapidly with news solutions and markets which sometimes need to demonstrate their reliability. The community needs to survey some evolutions such as the new exchange format, the faster 3D printing systems, the advanced numerical simulation or the emergence of new use. This review is addressed to persons who wish have a global view on the AM and improve their understanding. We propose to review the different AM technologies and the new trends to get a global overview through the engineering and manufacturing process. This article describes the engineering and manufacturing cycle with the 3D model management and the most recent technologies from the evolution of additive manufacturing. Finally, the use of AM resulted in new trends that are exposed below with the description of some new economic activities.

Additive manufacturing (AM) of high-resolution components for applications in the defense, aerospace, power generation, propulsion, and biomedical industries has led to accelerated design and production schedules of these parts as well as geometric flexibility, leading to the development of more complex component designs. AM technologies use a digital solid model (e.g., Computer-aided design, CAD) to develop a component layer-by-layer, with layer thickness varying depending upon the material used during manufacturing. Among the most commonly used AM processes are the powder-bed technologies, which include selective laser sintering (SLS), direct metal laser sintering (DMLS), electron beam melting (EBM), and selective laser melting (SLM), from which a variety of alloys such as Inconel 718 (IN718), Stainless Steel 316L and Ti-6Al-4V can be produced. The SLM process involves selectively melting metal powder by a high-energy laser within an inert gas (nitrogen or argon) environment. The focus of 226this review is on understanding the effect of SLM processing parameters on the microstructure and mechanical properties of Ni-based superalloys commonly used in the manufacturing of components subjected to elevated temperatures. The main goal here is to highlight the developments and to reflect on further research needed to better understand the SLM AM process. In addition to this review, this paper will present simulated elastoplastic tensile stress-strain response of SLM Inconel 718 and heat-treated SLM Inconel 718 exhibiting anisotropy, based upon mechanical properties found in literature. It will also discuss the viability of using the resulting tensile stress-strain response trends observed for SLM Inconel 718 and heat-treated SLM Inconel 718, to model a first-order approximation of the elastic behavior (e.g., Young’s Modulus) response with build orientation.

Ultrafine-grained and heterostructured materials are currently of high interest due to their superior mechanical and functional properties. Severe plastic deformation (SPD) is one of the most effective methods to produce such materials with unique microstructure-property relationships. In this review paper, after summarizing the recent progress in developing various SPD methods for processing bulk, surface and powder of materials, the main structural and microstructural features of SPD-processed materials are explained including lattice defects, grain boundaries and phase transformations. The properties and potential applications of SPD-processed materials are then reviewed in detail including tensile properties, creep, superplasticity, hydrogen embrittlement resistance, electrical conductivity, magnetic properties, optical properties, solar energy harvesting, photocatalysis, electrocatalysis, hydrolysis, hydrogen storage, hydrogen production, CO2 conversion, corrosion resistance and biocompatibility. It is shown that achieving such properties is not currently limited to pure metals and conventional metallic alloys, and a wide range of materials are processed by SPD, including high-entropy alloys, glasses, semiconductors, ceramics and polymers. It is particularly emphasized that SPD has moved from a simple metal processing tool to a powerful means for the discovery and synthesis of new superfunctional metallic and nonmetallic materials. The article ends by declaring that the borders of SPD have been extended from materials science and it has become an interdisciplinary tool to address scientific questions such as the mechanism of geological and astronomical phenomena and the origin of life.

Cerebral activity during number comparison was studied with functional magnetic resonance imaging using an event-related design. We identified an extended network of task-related areas that showed a phasic activation following each trial, including anterior cingulate, bilateral sensorimotor areas, inferior occipito-temporal cortices, posterior parietal cortices, inferior and dorsolateral prefrontal cortices, and thalami. We then tested which of these areas were affected by number notation, numerical distance and response side, three variables that specifically target processes of visual identification, quantity manipulation and motor response in a serial-stage model of the number comparison task. Our results confirm the role of the right fusiform gyrus in digit identification processes, and of the inferior parietal lobule in the internal manipulation of numerical quantities.

Additive Manufacturing or 3D Printing has a great potential to develop significant advances in materials, printers’ technology, and processes. Thus, the layer by layer manufacturing has existed for three decades and new developments recently appeared in smart materials. Laboratories discovered ways to design and manufacture advanced structured materials and responsive materials used in multi-functional and high-performance products. The current research and development efforts will have an impact on the traditional design and manufacturing process. 4D Printing announces a major modification in the product design and manufacturing process from static structures to dynamic structures like Shape Memory Material (SMM) with integrated functionalities. This article presents a review of smart materials based on a classification of advanced structured materials and responsive materials before beginning a description of current applications. The use of multi-materials and the study of predictive models to simulate the responsive materials behaviour accelerate the smart materials development.

BACKGROUND: The aims of this study were to investigate the effects of implant microthreads on crestal bone stress compared to a standard smooth implant collar and to analyze how different abutment diameters influenced the crestal bone stress level. METHODS: Two-dimensional finite element imaging was used to create a cross-sectional model of an implant (5-mm platform and 13 mm in length) placed in the premolar region of the mandible. The two tapered implant models consisted of one with microthreads at the crestal portion and the other with a smooth neck. The implant model was reverse-engineered to resemble a commercially available microthread implant. Abutments of different diameters (4.0 mm: 20% platform switching; 4.5 mm: 10% platform switching; and 5.0 mm: standard) were loaded with a force of 100 N at 90 degrees vertical and 15 degrees oblique angles. Finite element analysis was used to analyze the stress patterns in bone, especially in the crestal region. RESULTS: Upon loading, the microthread implant model had 29% greater stress (31.61 MPa in oblique and 9.31 MPa in vertical) at the crestal bone adjacent to the implant than the smooth-neck implant (24.51 and 7.20 MPa, respectively). When the abutment diameter decreased from 5.0 to 4.5 mm and then to 4.0 mm, the microthread model showed a reduction of stress at the crestal bone level from 6.3% to 5.4% after vertical loading and from 4.2% to 3.3% after oblique loading. The smooth-neck model showed a reduction of stress from 5.6% to 4.9% after vertical loading and from 3.7% to 2.9% after oblique loading. CONCLUSIONS: Microthreads increased crestal stress upon loading. Reduced abutment diameter (i.e., platform switching) resulted in less stress translated to the crestal bone in the microthread and smooth-neck groups.

This paper gives a procedure to control the size variation in a mesh adaption scheme where the size specification (the so-called control space) is used to govern the mesh generation stage. The method consists in replacing the initial control space by a reduced one by means of size or metric. It allows to improve, a priori, the quality of the adapted mesh and to speed up the adaption procedure. Several numerical examples show the efficiency of the reduction scheme. © 1998 John Wiley & Sons, Ltd.

We use large-scale molecular dynamics simulations to investigate plastic deformation of semicrystalline polymers with randomly nucleated crystallites. The strain-softening regime is dominated by deformation of crystallites via reorientation of chain-folded lamellae toward the tensile axis, fragmentation of largest crystalline domains, and a partial loss of crystallinity. The strain-hardening regime coincides with unfolding of chains and recrystallization as a result of strain-induced chain alignment. These observed deformation mechanisms are consistent with experimental findings. We compare the tensile behavior of semicrystalline polymers with their amorphous counterparts at temperatures above and below the glass transition temperature.

To study effect of the different metal additive manufacturing techniques on microstructural evolution, phase constitution and the relationship between the microstructure and tensile behavior of pure Cu parts, components were manufactured by selective laser melting (SLM) technology and cold spraying (CS) technology, respectively. The microstructure of Cu parts was detected using an optical microscope (OM) and scanning electron microscopy (SEM). The XRD spectrum revealed that only Cu phase is formed in the SLM Cu and CS Cu samples. The microstructure of the SLM Cu samples is constituted by the polycrystalline grains with substructures including the columnar dendrites and the equiaxed structures. As for the CS Cu samples, only the equiaxed grains were detected. In terms of the main physical properties, the averaged electrical conductivity of SLM Cu sample is 41% IACS, while that of CS Cu sample is 73% IACS. For the microhardness, the mean microhardness value of the CS Cu and the SLM Cu samples is 144.2 ± 4.3 HV0.05 and 83.6 ± 5.2 HV0.05, respectively. With regard to the statistic mechanical properties, the yield strength (YS) and ultimate tensile strength (UTS) of the SLM Cu part is approximately 185.8 ± 6.1 MPa and 242.2 ± 8.2 MPa, respectively.

The cooling conditions used in the forming process of composite materials play an important role in the creation ofresidual stress. In this study, a new method for measuring residual stress in composite laminates is presented. Three cooling conditions were used to produce different residual stress levels. Residual stresses in [02/902]s and [08] laminate have been measured by the incremental holedrilling method combined with 3-D finite element modelling. A software which quickly calculates all the coefficients for each increment was developed. The automatic procedure can be used to calculate the calibration coefficient for any type oflaminate (ply number, mechanic characteristics,...) and whatever the number of increments and their depths. The different results show that this method provides access to the in-depth distribution and through thickness ofresidual stress in the laminate with a good accuracy and practicality.

Abstract Multiplier methods used to solve the constrained engineering optimization problem are described. These methods solve the problem by minimizing a sequence of unconstrained problems defined using the cost and constraint functions. The methods, proposed in 1969, have been determined to be quite robust, although not as efficient as other algorithms. They can be more effective for some engineering applications, such as optimum design and control of large scale dynamic systems. Since 1969 several modifications and extensions of the methods have been developed. Therefore, it is important to review the theory and computational procedures of these methods so that more efficient and effective ones can be developed for engineering applications. Recent methods that are similar to the multiplier methods are also discussed. These are continuous multiplier update, exact penalty and exponential penalty methods.

An indirect method for meshing parametric surfaces conforming to a user-specifiable size map is presented. First, from this size specification, a Riemannian metric is defined so that the desired mesh is one with unit length edges with respect to the related Riemannian space (the so-called ‘unit mesh’). Then, based on the intrinsic properties of the surface, the Riemannian structure is induced into the parametric space. Finally, a unit mesh is generated completely inside the parametric space such that it conforms to the metric of the induced Riemannian structure. This mesh is constructed using a combined advancing-front—Delaunay approach applied within a Riemannian context. The proposed method can be applied to mesh composite parametric surfaces. Several examples illustrate the efficiency of our approach. Copyright © 2000 John Wiley & Sons, Ltd.

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Surface mechanical attrition treatment (SMAT) technique was developed to synthesize a nanostructured surface layer on metallic materials for upgrading their overall properties and performance. In this paper, the grain refinement process during SMAT was investigated in materials with low stacking fault energies (SFE, Inconel 600 alloy and AISI 304 stainless steel) by means of transmission electron microscopy and high-resolution electron microscopy, respectively. Grain subdivision was performed by the interaction of mechanical microtwins with dislocations in Inconel 600. For AISI 304 stainless steel with a lower SFE, twin-twin intersections subdivide initial grains into refined blocks with sizes ranging from nanometers to submicrometers. Such grain subdivision processes of the interaction of microtwins with dislocations or microtwins obviously differ from those observed in the high SFE materials in which dislocation interactions predominate the grain refinement.

The bacterial community associated with the midgut of three Brazilian Lutzomyia longipalpis (Lutz & Neiva) populations, two from endemic areas for visceral leishmaniasis (Jacobina, Bahia State and São Luís, Maranhão State) and one from a non-endemic area (Lapinha Cave, Minas Gerais State), was identified. Five groups, 35 females each, from each population were separated; a total of 175 females per collecting area were analyzed. The species identification was based on molecular and traditional bacteriological methods. All bacteria were either affiliated to non-Enterobacteriaceae, such as Acinetobacter, Burkholderia, Flavimonas, Pseudomonas and Stenotrophomonas, or and to Enterobacteriaceae, such as Citrobacter, Enterobacter, Escherichia, Klebsiella, Serratia, Pantoea, Morganella and Weeksella. Stenotrophomonas was found to be associated with all three populations studied. In addition, Serratia spp., which are well documented as laboratory contaminant of insects, were detected only in the Jacobina population. We also discuss the impact of the colonization of insect gut by bacteria on the development and transmission of pathogens.

With the recent digitization of the construction industry, the management of a project, from the idea to the use phases, is now based on the Building Information Modelling System (BIM). While the use of BIM begins to show its effectiveness in building construction, it does not satisfy yet linear infrastructure domain. One of the requirements is to manage the infrastructure project data around a common information system, as defined by the Product Lifecycle Management (PLM) definition. Recent studies suggest the combined use of PLM and BIM for linear infrastructure construction projects such as roads and railways. The advent of new information technologies, such as Digital Twin, is promoting industrial digital transformation. Effective lifecycle management must now consider all phases of the project, especially Operations and Maintenance (O&M), where the use of the 3D model is no longer the digital model, but the digital duplicate of the Infrastructure. To facilitate the digital transition when projects are split into several phases, the linear infrastructure must be represented by one and only one Digital Twin during its life cycle.

In the present work, the standard monometallic localized surface plasmon resonance (LSPR) biosensing sensitivity is highly improved when using a new system based on glass substrates modified with high-temperature annealed gold/silver bimetallic nanoparticles (Au/Ag bimetallic NPs) coated with polydopamine films before biomolecule specific immobilization. Thus, different zones of bimetallic NPs are spatially created onto a glass support thanks to a commercial transmission electron microscopy (TEM) grid marker in combination with two sequential evaporations of continuous films of gold (4 nm) and silver (2 nm) and followed by annealing at 500 °C for 8 h. By using the scanning electron microscopy (SEM), it is found that annealed Au/Ag bimetallic NPs have uniform size and shape distribution that exhibited a sharper well-defined LSPR resonant peak when compared with that of monometallic Au NPs and thereby contributing to an improved sensitivity in LSPR biosensor application. The controlled micropatterns consisting of bimetallic particles are used in the construction of LSPR biochips for high-throughput detection of different concentrations of a model antigen named bovine serum albumin (BSA) on a single glass sample, with a lower limit of detection of 0.01 ng/mL under the optimized conditions.

Phase change material (PCM) based heat sink has the potential to be applied for the thermal management of electronic devices. Whereas, PCM suffers from a low thermal conductivity, which results in local overheating at the base of heat sink. To enhance thermal performance of heat sink, a structured porous material (SPM) used as thermal conductivity enhancer (TCE) is designed and fabricated, where 3D printing technique is adopted to achieve the fast and precise manufacture of SPM. The thermal response of heat sink using SPM with different porosities (80%, 85%, 90%, and 95%) is experimentally investigated at various heating power levels (8 W, 10 W, and 12 W). Results show that the use of SPM has a significant effect on thermal response of heat sink for electronic cooling system. Furthermore, the thermal behavior of heat sink can be further heightened by reducing the porosity of SPM, e.g., the heat sink using SPM with 80% porosity shows the highest enhancement ratio in all cases of present study. The increase of power level can result in the reduction of operation time of PCM-based heat sink. This study is of great significance for the design and application of SPM used in thermal management unit.

A new method combining Moire´ interferometry and the incremental hole-drilling method is developed to determine both uniform and nonuniform residual stress distribution in depth. The study is reported in two parts. In this first part, the theoretical development of the moire´ interferometry hole-drilling method is presented. The relationship between the in-plane surface displacements produced by introducing a blind hole and the corresponding residual stresses is established by employing the existing theoretical solution containing a set of undetermined coefficients. The coefficients are calibrated by the three-dimensional finite element method and they are processed nondimensionally for general use. The whole field in-plane surface displacements data Ux and Uy produced by the relaxation of residual stresses are obtained from moire´ interferometry after each increment of hole drilling. The high signal-to-noise ratio provided by moire´ interferometry allows accurate determination of fringe orders near the hole boundary which is essential for enhancing fidelity of residual stress determination. The experimental procedure to determine the signs of residual stresses is described and the accuracy of the method is also discussed.