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Powder Bed Fusion (PBF) is an Additive Manufacturing (AM) process. It is the layer by layer addition process. In the future, it is going to be manufactured all types of products used in automotive, aerospace, energy sectors and home appliances. These products can be produced using various AM methods. Few of them are Laminated Object Manufacturing, Powder Bed Fusion and Direct Energy Deposition, Stereolithography (SLA), and Solid Ground Curing (SGC). The present brief review is concentrated on working of PBF process only. It includes Direct Metal Laser Deposition (DMLS), Selective Laser Sintering (SLS), Selective Laser Melting (SLM), Electron Beam Melting (EBM) and Selective Heat Sintering (SHS). In these processes powder lay on the powder bed and it is also known as built platform. Laser used as heat energy source for SLS, SLM and DMLS processes. But EBM uses electron beam as source of energy. The SHS process uses heated thermal head for sintering plastic powders. SLS, DMLS and SHS are powder sintering processes. But SLM and EBM are powder melting processes. This review paper is also covered historical development and usage of technologies, CNC verses Additive Manufacturing/Rapid Prototyping, AM process chain, Classification of AM processes; advantages, disadvantages and applications of PBF process.

The present study aims at assessing the mechanical behavior of aluminum alloy (AA2024) subjected to exfoliation corrosion. The material was exposed to high temperature and subsequent low temperature (HLA) treatment and further the heat-treated samples were subjected to exfoliation corrosion for the duration of 48 and 96 h at room temperature. The HLA treatment increases the retention property of material in the corrosive environment. Further, hardness and impact strength was also increased under the corrosive environment with HLA treatment. In addition to the experimental investigation, a series of simple second-degree polynomial equations were developed to predict the various mechanical properties at different intervals of corrosion durations of AA2024 specimens subjected to HLA exfoliation corrosion.

The effect of machining parameters on the thrust force, torque and burr height while drilling Al 2618, Al2618 with 10% boron carbide (B4C) and Al2618 with 10%B4C and 5% graphite (Gr) hybrid composites are addressed. The composites are produced using a process of liquid metallurgy. The findings indicate that, feed rate had a significant impact on thrust force and the height of the exit burr. The Al2618 + 10% B4C-5%Gr reinforced hybrid composites exhibit smaller thrust force and burr height in contrast to the Al2618 + 10% B4C composite. The reduced thrust force, torque and burr height was due to the strong graphite surface lubrication properties. The chips produced while machining graphitic composites are discontinuous, and hence beneficial.

The present investigation was focused to evaluate the mechanical properties of AA7075 subjected to corrosion and heat treatment. Exfoliation corrosion has been used to infuse rapid corrosion on the material coupled with high temperature and subsequent low-temperature aging (HLA). It has been found that the localized corrosion pit formation occurs with HLA and corrosion exposure durations with substantial inter-granular changes and the formation of cracks. A significant reduction in mechanical properties was observed with HLA-treated samples subjected to corrosion. The material’s stiffness was increased due to HLA, and again within the corrosive environment, a decreasing trend was observed with immersion durations. A series of simple one-dimensional linear and polynomial equations were developed to determine the properties of AA7075 samples subjected to HLA and corrosion.

The heat transfer is assumed to take place in a porous medium under the influence of two sources such as a whole surface applied with hot temperature and another small strip of heating element being kept at left side of the cavity. The governing equations are derived from the basic principle of Darcy flow. The impact of the heating strip length is investigated with respect to its position at x = 0.25L of the cavity with L being the length of cavity. Finite element method is used to form a set of equations in algebraic form that can be solved easily with the help of a computer code. The solution is set with proper tolerance limit to get accurate results. The results indicate that the position of element has impact on the heat transfer from hot to cold surface.

This article is aimed to study the thermal energy transport phenomenon caused by heating the porous cavity at left vertical wall as well as an internal heating by a strip of varying length near the cooling surface. The internal heating strip that varies in length is kept at x = 3L/4 of the cavity where L is the overall cavity length. Finite element method is at the core of solution techniques which is employed along with triangular shaped elements. The solution is arrived by following an iterative method that depends on satisfying the equations to a predetermined error level. It is ensured that the results are accurate enough to predict the phenomenon under study. The main aim of the study is to understand what happens when the heating element is placed towards the right vertical surface. The results are described for physical and geometrical parameters of the problem being considered.

Recycling has been the fascinating topic among the researchers for all times. The present study shows the recycling of steel plant's solid wastes as blast furnace flue dust and sludge towards agglomeration and their use in the production of sinter. These wastes consist of metal oxides and coke fines as a valuable material with some alkali oxides. Using these wastes as it is in the form of fines exacerbate the further processing. Pellets of these wastes are prepared with three types of binders as molasses, dextrin and bentonite. The result reveals that properties as compressive strength, shatter strength, are better in the case of bentonite binder having the productivity of the disc pelletizer machine as 75. After that, these macro pellets used for sintering with iron ore and other ingredients in pot type, down draft laboratory grade sintering machine, which shows very high productivity and good mechanical properties of the sinter as well. The microstructural analysis reveals the presence of re-oxidized hematite and a little bit of a magnetite phase with some slag phases, which confirmed later by XRD analysis. Results also show the decrease in coke rate, i.e. coke consumption to produce sinter and at the same time, this process is highly eco-friendly.

The strain hardening behavior of five different steels of varying carbon content, ranging between 0.007 and 0.71%, such as an Interstitial free (IF), a microalloyed, and a low, medium and high carbon steels, have been critically examined using tensile loading. The test results for the IF and the microalloyed steels having only ferritic structure, exhibit a two-stage strain hardening behavior. On the other hand, the low, medium, and high carbon steels having a two-phase microstructure (ferrite-pearlite/cementite) exhibit three-stage strain hardening. A number of existing and frequently used empirical equations, such as the Hollomon, Ludwik, Ludwigson and Voce were used to explain the strain-hardening characteristics of these steels; however, none of the above could fully and satisfactorily explain the flow behavior especially at high strain region. In order to remedy this deficiency, a modification to Ludwigson equation has been suggested by the authors by introducing an extra exponential term to the existing Ludwigson equation. The modelled flow curves, on the basis of this proposed new equation, could explain the strain hardening behavior of these steels very satisfactorily over the entire strain range. In addition, the excellent matching of the flow curves, based on the proposed equation with the experimental flow curves of a number of metallic materials, as diverse as multiphase steel, TRIP-assisted steel, dual-phase steel, stainless steel (316L), Mg-alloy, Ti-alloy and a high entropy (Cantor) alloy, indicates its wider applicability.

12-Phosphotungstic acid supported on silica gel, zirconium sulfate, and a combination of silica gel and zirconium sulfate (50% w/w) were employed as solid acid catalysts for regioselective acylation of 2-methoxynaphtalene with acetic anhydride. 1-(6-Methoxynaphthalen-2-yl)ethanone (2,6-AMN), a commercially important intermediate for production of Naproxen, was obtained with excellent selectivity (>98%) at 67–68% conversion using 12-phosphotungstic acid supported on silica gel 20% (w/w) in refluxing tetrachloroethane. The unreacted starting material can be easily separated from the product by a simple crystallization from nonane.

Resume Objectif Analyser les aspects epidemiologiques, anatomocliniques, chirurgicaux et evolutifs des complications urologiques de la chirurgie gynecologique. Patientes et methodes Il s’agissait d’une etude retrospective, concernant 81 patientes hospitalisees dans le service d’urologie du CHU de Brazzaville de 2000 a 2008 pour complications urologiques de la chirurgie gynecologique. Les parametres epidemiologiques, diagnostiques, chirurgicaux et evolutifs ont ete analyses. Resultats Les complications urologiques de la chirurgie gynecologique etaient retrouvees chez 3 % des patientes hospitalisees en urologie. L’âge moyen etait de 37 ± 14,52 ans (17et 74 ans) la mediane etait de 36 ans. Le delai moyen de diagnostic etait de 15 jours (0 et 350 jours). Les signes cliniques revelateurs etaient : l’oligoanurie ( n = 12), l’incontinence urinaire ( n = 57), la douleur lombaire ( n = 9) et l’hematurie cyclique ( n = 2). Les interventions chirurgicales en cause etaient : la cesarienne ( n = 50), l’hysterectomie ( n = 26), la myomectomie ( n = 3) et l’hysterectomie pour cancer ( n = 2). Les lesions observees ont ete 55 (67,9 %) fistules vesico-vaginales, 12 (14,8 %) ligatures ureterales, huit (10 %) fistules uretero-vaginales, trois (3,7 %) fistules vesico-uterines, deux (2,4 %) plaies ureterales et une (1,2 %) fistule vesico-vaginales et uretero-vaginale. Le traitement avait consiste en une ureterorraphie termino-terminale, 20 reimplantations ureterovesicales, 57 cures de fistules vesico-vaginales et une nephrectomie. La guerison avait ete obtenue chez 96 % des lesions ureterales et 90 % des fistules vesico-vaginales. Conclusion Les lesions de l’uretere et de la vessie etaient souvent rencontrees au cours de la chirurgie gynecologique. La prise en charge necessite des connaissances de l’anatomie du petit bassin.

Racemic 2-chlorophenyl glycine has been resolved to obtain (S)-α-amino-(2-chlorophenyl)acetic acid with >99% enantiomeric purity via enantioselective hydrolysis of its N-phenylacetyl derivative with penicillin G acylase immobilized on Eupergit C. The resolution can be conveniently performed in water at substrate concentration of 10% in 5 h with an enzyme:substrate ratio of 1:5 (w/w), and the enzyme can be recycled >25 times without any loss of activity. The unwanted (R)-enantiomer can be easily racemized for recycling.

A crude extract of Mung bean meal ( Phaseolus radiatus ) possessing epoxide hydrolase activity immobilized in gelatin gel (gelozyme) is employed in the stereoselective epoxide ring opening of glycidate esters. Thus, ethyl trans -(±)-3-phenyl glycidate 1a and methyl trans -(±)-3-(4-methoxyphenyl) glycidate 1b gave (2 S ,3 R )-glycidate esters (ee >99% and 45% yield) with gelatin immobilized enzyme in diisopropyl ether. The corresponding (2 R ,3 S )-enantiomer of 1a was hydrolyzed by an epoxide hydrolase to predominantly give the anti -product, ethyl (2 R ,3 R )-2,3-dihydroxy-3-phenylpropanoate, with a diastereomeric excess of 78% and ee 94% (40%). A small amount (5%) of racemic syn -product was also obtained as a result of the spontaneous hydrolysis. In the case of 1b , the hydrolysis product was racemic due to high reactivity of the glycidate toward water.

Our previous article (Part I) discussed the theoretical and experimental study of the performance boost obtained by a cooking vessel with central cylindrical cavity on lugs when compared to that of a conventional cylindrical vessel on floor/lugs. This article compares the performance of the cooking vessel with depressed lid on lugs with that of the conventional vessel on lugs. A mathematical model is presented to understand the heat flow process to the cooking vessel and, thereby, to the food material. It is found from the experiments that the cooking vessel with depressed lid results in higher temperature of the thermic fluid loaded in the cooking vessel compared to that of the thermic fluid kept in the conventional vessel when both are placed on lugs. Similar results were obtained by modeling the process mathematically. The average improvement of performance of the vessel with depressed lid is found to be 8.4% better than the conventional cylindrical vessel.

The performance of conventional box type solar cookers can be improved by better designs of cooking vessels with proper understanding of the heat flow to the material to be cooked. An attempt has been made in this article to arrive at a mathematical model to understand the heat flow process to the cooking vessel and thereby to the food material. The mathematical model considers a double glazed hot box type solar cooker loaded with two different types of vessels, kept either on the floor of the cooker or on lugs. The performance of the cooking vessel with a central cylindrical cavity is compared with that of a conventional cylindrical cooking vessel. It is found from the experiments and modeling that the cooking vessel with a central cylindrical cavity on lugs results in a higher temperature of the thermic fluid than that of a conventional vessel on the floor or on lugs. The average improvement of performance of the vessel with a central cylindrical cavity kept on lugs is found to be 5.9% and 2.4% more than that of a conventional cylindrical vessel on the floor and on lugs, respectively.