SPIF-A: on the development of a new concept of incremental forming machine

R.J. Alves de Sousa,J.A.F. Ferreira,J.B. Sá de Farias,J.N.D. Torrão,D.G. Afonso,M.A.B.E Martins 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.5

This paper presents the design and project of an innovative concept for a Single PointIncremental Forming (SPIF) Machine. Nowadays, equipment currently available for conducting SPIF resultmostly from the adaptation of conventional CNC machine tools that results in a limited range of applicationsin terms of materials and geometries. There is also a limited market supply of equipment dedicated toIncremental Sheet Forming (ISF), that are costly considering low batches, making it unattractive forindustry. Other factors impairing a quicker spread of SPIF are large forming times and poor geometricalaccuracy of parts. The following sections will depict the development of a new equipment, designed toovercome some of the limitations of machines currently used, allowing the development of a sounding basisfor further studies on the particular features of this process. The equipment here described possesses sixdegrees-of freedom for the tool, for the sake of improved flexibility in terms of achievable tool-paths and anextra stiffness provided by a parallel kinematics scheme. A brief state of the art about the existing SPIFmachines is provided to support the project’s guidelines.

SPIF-A: on the development of a new concept of incremental forming machine

Alves de Sousa, R.J.,Ferreira, J.A.F.,Sa de Farias, J.B.,Torrao, J.N.D.,Afonso, D.G.,Martins, M.A.B.E. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.5

This paper presents the design and project of an innovative concept for a Single Point Incremental Forming (SPIF) Machine. Nowadays, equipment currently available for conducting SPIF result mostly from the adaptation of conventional CNC machine tools that results in a limited range of applications in terms of materials and geometries. There is also a limited market supply of equipment dedicated to Incremental Sheet Forming (ISF), that are costly considering low batches, making it unattractive for industry. Other factors impairing a quicker spread of SPIF are large forming times and poor geometrical accuracy of parts. The following sections will depict the development of a new equipment, designed to overcome some of the limitations of machines currently used, allowing the development of a sounding basis for further studies on the particular features of this process. The equipment here described possesses six-degrees-of freedom for the tool, for the sake of improved flexibility in terms of achievable tool-paths and an extra stiffness provided by a parallel kinematics scheme. A brief state of the art about the existing SPIF machines is provided to support the project's guidelines.

An effective and facile synthesis of hydroxyapatite powders using oxalic acid―ethylene glycol mixture

D. Gopi,P.R. Bhalaji,V.C.A. Prakash,A.K. Ramasamy,L. Kavitha,J.M.F. Ferreira 한국물리학회 2011 Current Applied Physics Vol.11 No.3

A method to synthesize hydroxyapatite (HAP) ceramic powders using a metal-oxalate route with calcium chloride and phosphoric acid as calcium and phosphorus precursors respectively is described. Ethylene glycol was used as a reaction medium and oxalic acid as a chelating agent. The resulting HAP powders were calcined at 600 ℃ for 6 h and subsequently sintered at 900 ℃ for 2 h. FT-IR, XRD and SEM techniques were employed for the characterization of the synthesized particles. Moreover, the influence of reaction temperature on the HAP formation was also studied. The results have shown successful formation of the crystalline, uniform sized, uniform shaped and stoichiometric HAP powders at a reaction temperature of 75 ℃ which was found to be the optimum temperature for the preparation. The grain size of the synthesized sample was 680 nm in length and 440 nm in width.

A Sectional Matrix Method for IPT Coil Shape Optimization

Venugopal Prasanth,Pavol Bauer,J.A. Ferreira 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

In this paper, Neumann’s integral is evaluated for computing self-inductance using a multi-turn sectional matrix method. Analytical equations are derived considering the increase in dimensions of the coil due to an impinging air-gap between the turns. The resulting sectional self-inductance matrix is computed and the concepts of sectional partial self-inductance and sectional partial mutual inductance are introduced. The effects of the various partial inductances are considered as a function of the air-gap, dimensions and turns. Further, the mutual inductance of a pair of coils is considered and the coupling is obtained analytically. The coils considered are to be used for shape optimization of IPT coils. Finally, the results are compared with experimentation. This technique being generic can be applied to a number of different polygonal shapes and can be further simplified by the theory of vector decomposition of current elements. A case study with self-inductance and perimeter as optimization objective is considered.

Sustainability of kraft pulp mills: Bleaching technologies and sequences with reduced water use

A.M. Sousa,I.S.S. Pinto,L. Machado,L. Gando-Ferreira,M.J. Quina 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.125 No.-

The Kraft pulp industry is a relevant industrial sector in many countries with a considerable social, economic,and environmental impact. Thus, sustainability is the adequate framework to address this activitysector. This work presents a review of the literature, with a particular focus on the bleaching area and itsrelevance in reducing water use. The sustainability reports of the most prominent pulp and paper companieswere analyzed, considering their specific water utilization and the sustainability targets they haveoutlined. The most industrially applied bleaching sequences were also addressed and the stages of thestate-of-the-art sequences were analyzed (elemental chlorine free – ECF bleaching). Moreover, in thisreview, a detailed analysis of a sequence used on an industrial scale was carried out, highlighting thewashing steps and the measures that are taken to minimize water use. The main limitations to the minimizationof water use were identified, being deposit formation the major problem. Measures to overcomethese limitations, as well as future perspectives were discussed. Due to the shortage offreshwater nearby some pulp and paper production sites, there will continue to be great pressure inthe future to reduce water utilization, especially in the bleaching area.

Energy Requirements for Maintenance and Growth of Male Saanen Goat Kids

Medeiros, A.N.,Resende, K.T.,Teixeira, I.A.M.A.,Araujo, M.J.,Yanez, E.A.,Ferreira, A.C.D. Asian Australasian Association of Animal Productio 2014 Animal Bioscience Vol.27 No.9

The aim of study was to determine the energy requirements for maintenance and growth of forty-one Saanen, intact male kids with initial body weight (BW) of $5.12{\pm}0.19$ kg. The baseline (BL) group consisted of eight kids averaging $5.46{\pm}0.18$ kg BW. An intermediate group consisted of six kids, fed for ad libitum intake, that were slaughtered when they reached an average BW of $12.9{\pm}0.29$ kg. The remaining kids (n = 27) were randomly allocated into nine slaughter groups (blocks) of three animals distributed among three amounts of dry matter intake (DMI; ad libitum and restricted to 70% or 40% of ad libitum intake). Animals in a group were slaughtered when the ad libitum-treatment kid in the group reached 20 kg BW. In a digestibility trial, 21 kids (same animals of the comparative slaughter) were housed in metabolic cages and used in a completely randomized design to evaluate the energetic value of the diet at different feed intake levels. The net energy for maintenance ($NE_m$) was $417kJ/kg^{0.75}$ of empty BW (EBW)/d, while the metabolizable energy for maintenance ($ME_m$) was $657kJ/kg^{0.75}$ of EBW/d. The efficiency of ME use for NE maintenance ($k_m$) was 0.64. Body fat content varied from 59.91 to 92.02 g/kg of EBW while body energy content varied from 6.37 to 7.76 MJ/kg of EBW, respectively, for 5 and 20 kg of EBW. The net energy for growth ($NE_g$) ranged from 7.4 to 9.0 MJ/kg of empty weight gain by day at 5 and 20 kg BW, respectively. This study indicated that the energy requirements in goats were lower than previously published requirements for growing dairy goats.

Design of a Medium Frequency Transformer with High Insulation Level for Dual Active Bridge DC-DC Converter

Tianzhu Tang,J.A.Ferreira,Saijun Mao,Wenbo Wang,M.Ghaffarian Niasar 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper presents a medium frequency transformer with high insulation level design which is used for the DAB DC-DC converter. The transformer size is largely reduced when operating at medium frequency compared with conventional power frequency transformer which provides the possibility for higher power density. However, there is a trade-off between the high power density and thermal performance. First of all, the exposed cooling surface is reduced accordingly. And the dissipated heat is proportional to the exposed cooling surface directly. Secondly with higher frequencies, effects such as skin and proximity and hysteresis losses are significantly increased compared to transformer operation at 50/60 Hz. Besides the design process should consider high isolation requirement. And this again defects the transformer thermal performance and this is because firstly insulation material adds extra losses to the system, secondly the construction of the insulation will block some cooling surfaces and thirdly those insulation materials normally have relatively low thermal conductivity. As a consequence, the thermal design should be carefully considered and evaluated. To solve this problem, only the high voltage side winding is impregnated in epoxy resin which reduces the insulation material. The stacked transformer cores are gapped from each other which have helped the transformer heat dissipation. Such that, a design with low thermal resistance and high power density is achieved. FEM models are developed to analyze the transformer electric and thermal performances. Finally prototypes are built and tested to verify our design concept.

SiC JFET Switching Behavior in a Drive Inverter under Influence of Circuit Parasitics

I. Josifovi?,J. Popovi?-Gerber,J.A. Ferreira 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

This paper investigates the switching behaviour of normally-off SiC JFETs in an inverter for a motor drive. The parasitic ringing caused by different parasitic effects is analysed. Two different methods, the use of an RC snubber and the use of a ferrite bead, are proposed for dampening the parasitic oscillations. It is found that applying a ferrite bead not only dampens the parasitic oscillations but also results in significantly lower switching losses. Furthermore, it is shown that the capacitive coupling between SiC devices and heat sinks significantly deteriorates the JFETs’ switching performance. The effect of two substrates, an IMS and a PCB, on the capacitive coupling is investigated. A method in which the use of two separate heat sinks minimises the capacitive coupling thus exploiting the full potential of fast SiC JFETs is proposed.

Two Operational Modes of the Modular Multilevel DC Converter

K. Huang,J.A. Ferreira 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Due to the increasing application of high voltage dc transmission, bidirectional dc to dc converters for high voltage applications will play a key role in future power grids. The recently presented modular multilevel dc converter (M2DC) is a new topology suitable for highvoltage bidirectional dc conversion. Two operational modes-inductive coupled mode and resistive coupled mode-of the M2DC are defined according to the characteristic of the arm impedance. Transfer functions of both operational modes are theoretically derived, which show that the M2DC could be configured to be either voltage source or current source. This feature offers the M2DC full controllability over output voltage and output current, making it suitable for different application scenarios. Simulation and experimental results of a 4 submodules tuned filter version M2DC are presented for verification of its functions.

Optimization of a Flywheel PMSM with an External Rotor and a Slotless Stator

Holm S.R,Polinder H.,Ferreira J.A. The Korean Institute of Electrical Engineers 2005 KIEE International Transactions on Electrical Mach Vol.b5 No.3

An electrical machine for a high-speed flywheel for energy storage in large hybrid electric vehicles is described. Design choices for the machine are motivated: it is a radial-flux external-rotor permanent-magnet synchronous machine without slots in the stator iron and with a shielding cylinder. An analytical model of the machine is briefly introduced whereafter optimization of the machine is discussed. Three optimization criteria were chosen: (1) torque; (2) total stator losses and (3) induced eddy current loss on the rotor. The influence of the following optimization variables on these criteria is investigated: (1) permanent-magnet array; (2) winding distribution and (3) machine geometry. The paper shows that an analytical model of the machine is very useful in optimization.