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Monte-Carlo and sensitivity transport models for domain deformation
No full textInternational audienceWe address the question of evaluating shape derivatives of objective functions for radiative-transfer engineering involving semi-transparent media. After recalling the standard Monte-Carlo approach to sensitivity estimation and its current limitations, a new method is presented for the specific case of geometrical sensitivities. This method is then tested on configurations with multiple-scattering and absorbing (non-emitting) semi-transparent medium. A new geometrical sensitivity algorithm is presented with full details in order to extend, on several examples, its implementation in complex geometries
Heat treatments design for superior high-temperature tensile properties of alloy 625 produced by Selective Laser Melting
No full textInternational audienceThe popular superalloy Alloy 625 was produced by Selective Laser Melting (SLM) and post-processing heat treatments were designed to optimize the inhomogeneous and constrained as-built microstructure (AB) for high temperature structural applications. A single-step solution heat treatment (RX) was designed to promote full recrystallization and approach the conventional wrought microstructure. To enhance high temperature properties, a grain boundary serration heat treatment (GBS) was successfully designed involving higher solution temperature and time to promote recrystallization and homogeneity, and a direct slow cooling step followed by a short aging to assist solute diffusion and grain boundary motion. The resulting microstructures were characterized by fully recrystallized fine equiaxed grains and fine intra and intergranular NbC precipitates. The GBS alloy also exhibited as much as 80% of serrated grain boundaries with enhanced resistance to cracking at high temperatures. Tensile properties of all three materials were evaluated at room temperature, 500 °C, 600 °C and 700 °C and compared with their conventional solutionized wrought Alloy 625 counterpart (Wrought). While the AB material exhibited high strength and low ductility, due for the most part to the high density of tangled dislocations resulting from SLM, both RX and GBS alloys showed tensile properties comparable to the conventional wrought material, higher strength in particular. At all temperatures, all four alloys exhibited yield strength values well over 200 MPa. Due to significantly different microstructures, deformation and fracture behaviors were different. While Wrought clearly presented irregular plastic flow at elevated temperatures typically attributed to dynamic strain aging (DSA), the materials produced by SLM and moreover those subjected to post-processing heat treatments exhibited more stable plastic deformation. The results and characterization reported in the present article highlight the predominant role of microstructure and outstanding potential of SLMed Alloy 625
Study of the Two Steps and One-Pot Two-Step Mechanochemical Synthesis of Annulated 1,2,4-Triazoles
No full textInternational audienceThe mechanochemical synthesis of 1,2,4-triazoles by using a planetary ball-mill is studied starting from hydralazine hydrochloride. Excellent conditions were found for achieving total conversion to intermediate hydrazones in a few minutes in the presence of pyrogenic S13 silica as grinding auxiliary. The conversion to annulated 1,2,4-triazoles was optimal with iodobenzene diacetate (IBD) when using nonphenolic hydrazones, while SeO2 was found to be efficient for phenolic compounds. The one-pot two-step synthesis was also successfully conducted for the first time leading to annulated 1,2,4-triazoles. Finally, green metrics showed the efficiency of the method in comparison to the conventional syntheses of hydrazone 10 and triazole 13
Automotive Chassis Design Material Selection for Road and Race Vehicles
No full textInternational audienceAutomotive chassis design, development is quite important in today’s environment. This work is oriented towards analysis of a ladder chassis and space frame chassis design. The analysis of the designed models involves the use of three different materials. In this investigation two different conditions of vehicle loading are considered namely un-laden (without passengers that is the KERB weight of the vehicle) condition and the laden (with passengers and miscellaneous weight also called gross weight) condition. Analysis had resulted with various variables of stress indicating the stress levels minimum in unladen case as 3.00E-17 and maximum in laden case as 29.8662, in case of space frame analysis the stress in minimum for steel with laden chasis as 0.001558 and maximum in case of composite material as 7.8447. These results would be useful with in selection of material for automotive frames
Insights in mechanisms of carbonaceous microparticles formation from black liquor hydrothermal conversion
No full textInternational audienceThe study addresses the formation of secondary hydrochar and the morphology of secondary microparticles from black liquor. The black liquor solution was hydrothermally converted at 350 °C and 16.5 MPa in batch reactors running from 15 min to 24 h at different heating and cooling rates. Spherical carbon microparticles were obtained at a short reaction time (< 90 min) and then coalesced to form aggregates. At a very long reaction time (24 h), spherical carbon microparticles were obtained once again. The carbonaceous solid was enriched in carbon during the first 4 hours of reaction. In parallel, the concentrations of total organic carbon and total phenols in the solution decreased drastically. The formation of solids was mainly due to chemical reactions occurring during the first 4 hours. Subsequent changes in the solids were mainly due to physical reorganization since the chemical compositions of solutions were almost stable
BPRIM: An integrated framework for business process management and risk management
No full textInternational audienceEnterprise engineering deals with the design of processes which aim to improve the structure and efficiency of business organizations. It develops approaches based on modeling techniques, particularly on business process modeling, to ensure the quality and the global consistency of enterprise strategies and expectations. Nowadays, risk consideration in enterprise engineering is a growing concern since the business environment is becoming more and more competitive, complex, and unpredictable. To face this concern, a paradigm named risk-aware business process management (R-BPM) has recently emerged. It seeks to integrate the two traditionally isolated fields of risk management and business process management. Despite the significant benefits that can arise from the use of R-BPM, it suffers from a lack of solid scientific foundations and dedicated tooling. This present research work contributes to bridging that gap in a twofold way: (i) by establishing the BPRIM Business Process-Risk Integrated Method framework, and (ii) by designing a dedicated tool, named adoBPRIM which supports the efficient application of the BPRIM framework. This paper first comprehensively presents the foundation of BPRIM which is based on three main components and, secondly, its dedicated tool adoBPRIM which was designed using the ADOxx meta-modeling platform. An evaluation with a real case study in the health care domain shows the relevance of the methodological framework
Green waste/ wood pellets pyrolysis in a pilot-scale rotary kiln: effect of temperature on product distribution and characteristics
No full textInternational audienceIn this study, a pilot-scale rotary kiln was used to perform the pyrolysis of garden green waste. The results are compared to wood pellets (a mixture of oak and beech sawdust). Both samples have similar organic composition and energy content except for ash content which is around three times higher in the case of green waste. Pyrolysis tests were performed at different temperatures ranging from 700 to 900°C. The study of the products yields as a function of temperature showed that above 700°C, volatile matter (gas and bio-oil) yields were higher than 80 wt.% and syngas (CO+H2) concentration was higher than 59 mol.%. On the other hand, the char yield was below 20 wt. % with an HHV of 29 MJ/kg and an 80% carbon content. Tar quantitative gas chromatography/mass spectrometry (GC/MS) analysis showed the predominance of benzene and naphthalene. Hence, this work revealed and validated the relevance of green waste thermochemical conversion for syngas production. In addition, this investigation can support the optimization of operating parameters and energy efficiency of a two-staged gasification process where pyrolysis is a decisive initial step
Thermomechanical coupling investigation in Ti-6Al-4V orthogonal cutting: experimental and numerical confrontation
No full textInternational audienceThe constant industrial need of detail data on the chip formation meets with the lack of a physical understanding of the thermo-mechanical couplings during hard metal cutting. In the present paper, numerical and experimental investigations at micro scale (about 0.5 × 0.5 mm2 area), is performed in order to highlight the mechanisms responsible for the poor Ti-6Al-4V machinability. In a first step, strain, strain-rates, temperatures, dissipated powers along with displacements, velocity and crack propagation are obtained at each pixel by means of VISIR apparatus. Experimental observations have highlighted the dependency of the physical phenomena to both cutting speed and rake angle and provide valuable evidences on the different nature of the coupling phenomenon. Secondly, a 3D FE orthogonal cutting model is then developed to bring a multi-scale comprehension of Ti-6Al-4V chip genesis and to predict the kinematics and thermal quantities. The numerical and experimental confrontation revealed the robustness of the developed FE model as well as its limits. Hence, the element deletion method and the friction model are identified as the main weak spots of the proposed FE model. Finally, a particular attention is paid to the chip formation steps and their impact on the final part
An investigation of the physical, thermal and mechanical properties of fired clay/SiC ceramics for thermal energy storage
No full textInternational audienceThermal energy storage (TES) has been identified as a breakthrough concept in development of renewable technologies. However, the main challenges are related to the development of competitive heat storage materials. Despite the number of studies on heat storage materials, the determination of new alternatives for next generation technologies is still open. In this regard, this paper presents the results of an experimental study of the physical, thermal and mechanical properties of SiC-doped ceramics as potential materials for TES applications. Two kinds of SiC additives (high and low densities) were incorporated with different percentages into the clay matrix in order to produce ceramics via the extrusion process. The addition of low-density SiC (true density 3.16 g cm−3) led to the increasing of porosity with large pore sizes and the decreasing of bulk density. Therefore, the thermal and mechanical properties are decreased up to − 50% for flexural strength and − 15% for thermal conductivity when 20 mass% of low-density SiC was used. On the other hand, when high-density SiC (true density 3.42 g cm−3) was used, properties of the clay ceramic were strongly improved: i.e., increase in the bulk density, decrease in the porosity, increase in the thermal conductivity and increase in the flexural strength. The best material was found with the addition of 20 mass% of high-density SiC which had a thermal conductivity of 1 W m−1 K−1, a specific heat capacity of 0.62 kJ kg−1 K−1 and a mechanical strength of 19.6 MPa. It also showed a high thermal stability after 20 successive heating/cooling cycles. Hence, this study provided a useful insight into how the SiC modified the microstructure and properties of fired clay ceramics. Thus, the current results suggest that clay ceramics with high-density SiC addition are promising materials for thermal energy storage application
Selective Hydrogenation of Carbon Dioxide into Methanol
No full textInternational audienceThis chapter is dedicated to methanol synthesis from carbon dioxide and hydrogen. Methanol, chemical formula CH3OH, is an important platform molecule which can be transformed into a large number of other chemicals, i.e., formaldehyde, acetic acid, dimethyl ether, methyl tert-butyl ether, and methyl methacrylate, as well as complex hydrocarbon mixtures, e.g., gasoline and diesel. Up to date, methanol is produced at industrial scale by steam reforming of natural gas, leading to high environmental impacts. The selective hydrogenation of carbon dioxide into methanol can be a good alternative since it is possible to capture carbon dioxide from industrial processes and to produce hydrogen from renewable energies, e.g., solar energy and wind energy.From a thermodynamic point of view, carbon dioxide hydrogenation is strongly influenced by the total pressure, temperature, and feeding composition. The use of a catalyst is also mandatory to control the kinetic and the selectivity into methanol. Among solid catalysts studied, copper-based catalysts have been found to be the best catalytic systems. Promoters like zinc oxide were usually used. Nickel-, palladium-, and silver-based catalysts also showed good catalytic performance compared to copper-based catalysts. Soluble catalysts have been intensively studied for this hydrogenation. Ru complexes appeared as the best homogeneous catalyst. Other metal-free homogeneous catalysts, e.g., N-heterocyclic carbenes, have been found to be active and selective in this reaction. Efforts have been made on the mechanistic study of the reaction in both the gas and liquid phases. Large industrial production has started in several countries showing the interest and the feasibility of the process