Safety Isolating Transformer Design using HyDE-DF algorithm

This paper presents an application of Evolutionary Computation (EC) to the benchmark of the safety isolating transformer problem. The benchmark adopts multidisciplinary optimization strategies, namely the multidisciplinary feasible (MDF) and the individual discipline feasible (IDF) formulations. The benchmark meets the requirements of engineers and scientists working with machine design problem, such as in the first part of the design process that is the choice of structure and materials. The EC methods employed in this paper are based on Evolutionary Algorithms (EAs), namely two variants of Differential Evolution (DE), two variants of Hybrid Adaptive DE (HyDE) and the Vortex Search (VS). The results showed in this paper suggest that EA methods are competitive with the classical optimization method, the sequential quadratic programming (SQP). Among the developed EAs, HyDE-DF is able to obtain better values than SQP on a significant battery of trials.This research has received funding from FEDER funds through the Op-erational Programme for Competitiveness and Internationalization (COM-PETE 2020), under Project POCI-01-0145-FEDER-028983;by NationalFunds through the FCT Portuguese Foundation for Science and Technology, under Projects PTDC/EEI-EEE/28983/2017 (CENERGETIC), and UIDB/00760/2020; Joao Soares is supported by FCT CEECIND/02814/2017grant.info:eu-repo/semantics/publishedVersio

Novel entropy-stabilized fluorite oxides with multifunctional properties

Development of new high-entropy oxides having configurational entropy dominating the phase stability has become a hot topic since the discovery of rock salt structure entropy-stabilized (ES)(MgCoNiCuZn)O in 2015. Herein, we report a set of novel entropy-stabilized fluorite oxides: Zr0.2Hf0.2Ce0.2Sn0.2Mn0.2O2-{\delta}, Zr0.2Hf0.2Ti0.2Mn0.2Ce0.2O2-{\delta}, Zr0.225Hf0.225Ti0.225Mn0.225Ce0.1O2-{\delta}, and Zr0.2Hf0.2Ti0.2Mn0.2Ce0.1Ta0.05Fe0.05O2-{\delta} synthesized using standard solid-state reaction. These compounds have been investigated using X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy techniques to discern their structural, microstructural, and chemical properties. The configurational-entropy dominated phase stability and hence the entropy stabilization of the compounds is confirmed by cyclic heat treatments. The mismatch in the ionic radii and oxidation state of the cations are the key factors in achieving a single-phase fluorite structure. Further, screening of physical properties including thermal conductivity, optical band gap, magnetic properties, and impedance spectroscopy is discussed. Thermal conductivity of 1.4-1.7 Wm-1K-1 is observed at 300 K and remains mostly invariant across a wide temperature range (300K-1073K), favorable for thermal barrier coating applications. These ES samples have an optical band gap of 1.6-1.8 eV, enabling light absorption across the visible spectrum and hence could be promising for photocatalytic applications. The impedance spectroscopy data of the entropy-stabilized samples reveal the presence of electronic contributions with small activation energy (0.3-0.4 eV) across a temperature range of 298K-423K. These observations in ES fluorite systems show potential for their multifunctional applications via further optimization and confirm the great chemical versatility of entropy-stabilized oxides.Comment: 13 Pages, 9 Figures 1 Tabl

Photonic titanium dioxide film obtained from hard template with chiral nematic structure for environmental application

International audienceIn the present work, mesoporous TiO 2 with a photonic structure was elaborated using cellulose nanocrystals (CNCs) as a biotemplate by two-step hard template methods. This strategy enables to replicate the chiral nematic (CN) structure of the photonic films (biotemplate) in TiO 2 films. A series of iridescent CNCs films with different weight ratios of silica/CNCs composite photonic films were prepared via evaporation induced self-assembly (EISA) method. The films showed iridescent color and tuneable Bragg reflection wavelengths by solely changing the ratio between the silica and the CNCs biotemplate. Polarized optical microscopy (POM) performed on hydride SiO 2 /CNCs films showed a birefringence and typical fingerprint of chiral nematic structure. This birefringence was also observed for TiO 2 films obtained using SiO 2 films as a hard template, which suggested the transfer of the chiral nematic structure in TiO 2 materials. Afterwards, their optical, morphological and electronic properties were studied by scanning electron microscope (SEM), POM, energy-dispersive X-ray spectroscope (EDX) and time resolved microwave conductivity (TRMC). The photocatalytic activities were evaluated by following the phenol degradation using high performance liquid chromatography (HPLC). The results showed that the structuration of the TiO 2 film using a chiral nematic SiO 2 film as hard template enhances the photocatalytic performance compared to non-structured mesoporous TiO 2

Optimization of microstructural evolution during laser cladding of Ni based powder on GCI glass molds

International audienceIn the glass industry, laser cladding is an innovative surfacing technique of depositing a layer of nickel to protect glass mold against corrosion, abrasion and thermal fatigue. This method (powder fusion by projection), well known in additive manufacturing represents a real technological leap for the glass industry. However, during laser cladding of Ni-based powder on gray cast iron, cracks can be observed for some process conditions. These cracks are often due to the Heat Affected Zone which creates structural stresses linked to the development of a martensitic structure in the ferritic matrix of the lamellar graphite cast iron. The aim of this work is to observe the impact of laser cladding (without substrate pre-heating usually used to limit cracking) on coating behavior but also on flake-graphite cast iron substrates. The microstructure and the mechanical properties were studied around the interface cladding/substrate. The impact of the processing parameters (power P, scanning speed v and powder feeding rate PFR was studied by using the ANOVA (ANalysis Of VAriance) technique. It has been observed that laser cladding on graphite cast iron without cracking is possible by limiting the linear energy induced by the process. Optimization of the processing parameters in order to obtain the industrial expected geometry of the coating has also been proposed

Study of the microstructure and texture heterogeneities of Fe–48wt%Ni alloy severely deformed by equal channel angular pressing

International audienceA Fe-48wt%Ni alloy was processed by severe plastic deformation using equal channel angular pressing process. A stacking of 9 sheets was introduced and pressed up to two passes into die with an inner angles of Φ=90º and outer arc of curvature ψ= 17° at room temperature following route A. The same material in bulk form was also ECAPed up to one pass. The microstructure and the texture were investigated by means of electron backscattered diffraction and X-ray diffraction, respectively. To evaluate the mechanical response, Vickers microhardness was carried out. The given analyses concern the as-received sample, the peripheral and the central plates of the pressed stacks and the upper, the middle and the lower parts of the pressed bulk material. The deformation was heterogeneous and variations in texture and microstructure, resulting from different efficiencies in the shearing process, were locally noted. For the stacks samples, the microstructure evolved from equiaxed grains of 9 μm with high fraction of high-angle grain boundaries (around 90%) to a heterogeneous fine grain structure with an average grain size of 3 m after two passes. On the contrary, for the bulk sample, the evolution wa

Recrystallization and grain growth at the interface of a bimetallic colaminated strip composed of two different Fe-Ni alloys

International audienceRoll bonding is a solid-state welding process widely used to manufacture layered metal composites. Particular properties may thus be obtained using the physical features of each material of the composite. Bimetal plates consisting of two different Fe-Ni alloys were made by roll bonding followed by heat treatment for 90 minutes at various annealing temperatures. The effects of post-rolling heat treatments on the bonding strength of a bimetal strip were investigated in relation to the interface microstructure evolution. Both recrystallization and grain growth took place at the interface during annealing. In particular, nucleation of new grains as well as growing grains crossing the interface may have contributed to the improvement of the bonding strength. Moreover, diffusion through the interface was found to drastically enhance the bonding strength from 850°C up to 1050°C. However, excessive grain growth associated to porosity occurrence probably caused the saturation of the bonding strength beyond 1050°C

Microstructure, Texture, and Mechanical Properties of Ni-W Alloy After Accumulative Roll Bonding

International audienceIn this study, the microstructure, texture, and mechanical properties evolution of Ni-14W (wt. %) alloy processed up to four cycles of accumulative roll-bonding (ARB) were investigated using electron backscatter diffraction, microhardness measurements, and tensile tests. The initial equiaxed grains, with an average size of 10 μm, underwent a strong refinement after ARB processing. The elongated ultrafine grains were parallel to the rolling direction, with a grain thickness of 0.2 µm. The texture after ARB processing was characterized by the typical rolling components (Copper, S and Brass), which showed a tendency toward stabilization after four cycles. The microhardness increased substantially (+86%) and seemed to saturate after three cycles. The tensile tests demonstrated that Ni-14W samples subjected to ARB processing exhibited high strength (> 1200 MPa after three ARB cycles) and very poor ductility

Microstructural Evolutions and Mechanical Properties of Drawn Medium Carbon Steel Wire

International audienceThis study focuses on the evolution in the microstructure, texture and mechanical properties of medium carbon steel wires obtained by wire drawing at Tréfissoud Company for the manufacturing of the spring mattress. Wire drawing induces elongation of grains in the direction of drawing with the development of the fibre texture parallel to the wire axis. Kinking and bending of cementite lamellae were observed during the drawing process. The work was carried out respectively on three states, wire rod and drawn states for two different amounts (ε %=43,6 and 60 %), using the optical and SEM microscopy, electron backscatter diffraction and X-ray diffraction analysis for examination of the microstructure and texture evolution, the hardness Vickers and tensile test to follow the curing of the studied wires

L’EBSD : historique, principe et exemples d’applications

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Pulse energy dependence of refractive index change in lithium niobium silicate glass during femtosecond laser direct writing

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