Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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Artigo 0 Citação(ões) na Scopus Silício: Abundante, eclético, sofisticado(2004-01-04) PAPALEO, R.Artigo 2 Citação(ões) na Scopus Using linear programming for the optimal control of a cartpendulum system(2011-01-05) PUGLIA, L. V.; Fabrizio Leonardi; Marko AckermannThis paper discusses the use of linear programming for the optimal control of a cart pendulum system. The objective function and the constraints are designed to minimize the control effort and the time duration of the operation. Simulations and experimental tests were performed. Restrictions of null angle and angular velocity at the extremes were incorporated in the design specification as well as other physical constraints. In order to compensate for the modeling errors and disturbances, the optimal trajectory was kept within a prescribed precision by means of a closed loop system. The obtained results illustrate that the technique is simple, powerful and always conclusive.Artigo 0 Citação(ões) na Scopus Reducing vibrations on flexible rotating arms through the movement of sliding masses: Modeling, optimal control and simulation(2012-01-05) TERCEIRO, E.; FLEURY, A. T.This paper brings contributions on the proposal of use of translational motions of sliding masses to minimize vibrations induced by the rotational motion of a light flexible manipulator (rotating arm). This system is inspired by rotating cranes used to transport loads. Optimal control methods have been used to generate the slider trajectories while the flexible manipulator performs a rotational maneuver from a fixed to other fixed configuration. This approach has led to good solutions even in case of quite quick maneuvers, as, for example, a 90° beam rotation in just 1 second, using 1 or 2 sliders (Terceiro, 2002). In the present paper, the complete motion equations for any number of masses are firstly presented, in order to emphasize the complexity of the coupled elastic-rotational-translational motions. Simplifying assumptions are pointed out and the corresponding optimal control problems (OCP) are obtained. Optimal trajectories, generated according to different Indexes of Performance and different problem parameters, are analysed and compared in order to get feasible movements for the set.Artigo 3 Citação(ões) na Scopus Automation course for industrial engineers: An approach based on Petri Nets, software tools and laboratory experiments(2014-01-05) Fabio Lima; PRADO, A. C.; Alexandre Augusto Massote; Fabrizio Leonardi© 2014 TEMPUS Publications.This paper proposes a methodology for teaching industrial automation to Brazilian industrial engineering undergraduate students, based on analysing a computational solution associated with an integrated manufacturing laboratory. As a first approach an analytical analysis of the automated process is carried out. Then the manufacturing laboratory is combined with software tools, to provide the industrial engineering student with a powerful analysis for using these kinds of systems to improve product quality and production performance. For the computational analysis, we have inserted Petri Nets to evaluate the production system performance with a good acceptance from the students. This is the highlight of this work since using Petri Nets for Industrial Engineering undergraduate students is not a common approach. Finally, an assessment proved that such a strategy has been producing excellent learning results.- Crack tunneling effects on the elastic unloading compliance of C(T), SE(B) and clamped SE(T) specimens and correction methodology(2023) ANDRE, L. G. F.; MATTAR NETO, M.; Gustavo Donato© 2023 Elsevier LtdThis paper covers the effects of crack tunneling on SE(B), C(T), and clamped SE(T) specimens and presents a correction methodology for this effect and is divided in two parts. Part one presents an investigation of how crack front curvature affects instantaneous crack size predictions based on the elastic unloading compliance technique. Relative crack depths (a/W) of 0.2, 0.5, and 0.7, were considered alongside five levels of crack curvature. Refined finite element models provided load-CMOD records in order to support compliance assessment. The crack front was modeled as a semi-ellipse, and the compliance results agreed with experimental data from the literature. It was shown that for the same equivalent physical straight crack standardized by ASTM, compliance generally decreases as tunneling increases. Since the maximum crack curvature allowed by the aforementioned standards is very restrictive, compliance did not meaningfully change within that limit, however, if violated, this paper shows that higher deviations may occur, leading to inaccurate crack depth estimations and invalid test results. These limits and deviations were clearly determined and, as a step to improve the techniques, this paper also presents – in part two – an exploration of a possible approach to mitigate this problem, which is based on the modification of how the equivalent straight crack of a curved crack front is determined. This new approach presents reduced errors in compliance-based crack size estimation as crack curvature increases when compared to current standardized protocols, and it can support further investigations in order to validate and standardize improved measuring techniques. Finally, it is important to state that even though the ASTM E1820 is used for the determination of crack driving forces, this study is based only on the study of the crack front curvature, the limit imposed by this standard and the deviations on crack size estimation when those limits are violated, while not focusing on determining errors directly on the J-integral. This paper is a further development on the studies published before by the research group.
- Indoor Airflow Dynamics in Compartmentalized Pneumology Units Equipped with Variable-Thickness MERV-13 Filters(2023-04-05) ALVES, C. G. A.; CHECHI JUNIOR, J. T.; Da SILVA NETO F.B.; ANJOS, G. R.; DOS SANTOS, M. D.; OLIVEIRA, G. P. DE© 2023 by the authors.Infection containment in the post-pandemic scenario became a top priority for healthcare engineering control staffers, especially in pneumology sectors, where the treatment of airborne infectious diseases is frequent. In Brazil, where COVID-19 left a long record of casualties, there is a lack of information on the influence of filtration systems on the maintenance of regulated operational conditions for indoor comfort in hospital environments. This paper has the following objectives: to study arrangements of filtering systems in hospital acclimatization ducts; to verify how filtering characteristics could compromise safety regulations for airflow in hospital environments; and to identify airflow stagnation points that might favor suspended viral concentrations and increase contamination risks. We used the computational fluid dynamics STAR-CCM+© software to perform numerical simulations of different cases of indoor airflow in a model corresponding to a sector of the Lauro Wanderley University Hospital (João Pessoa city, Brazil). We concluded that standards for maximum velocity are reachable despite thinner or thicker filters affecting the spread of the air. In this way, acclimatization systems are limited by a tradeoff between regulation and protection. Our findings are relevant to future technological development, interventions, safety strategies amidst contamination scenarios, and new filtration arrangements in hospital environments.
- What Facial Features Does the Pediatrician Look to Decide That a Newborn Is Feeling Pain?(2023-01-05) SILVA, G. V. T. D.; BARROS, M. C. M.; SOARES, J. D. C. A.; CARLINI, L. P.; HEIDERICJ, T. M.; ORSI, R. N.; BALDA, R. C. X.; Carlos E. Thomaz; GUINSBURG, R.Thieme. All rights reserved.OBJECTIVE: The study aimed to analyze the gaze fixation of pediatricians during the decision process regarding the presence/absence of pain in pictures of newborn infants. STUDY DESIGN: Experimental study, involving 38 pediatricians (92% females, 34.6 ± 9.0 years, 22 neonatologists) who evaluated 20 pictures (two pictures of each newborn: one at rest and one during a painful procedure), presented in random order for each participant. The Tobii-TX300 equipment tracked eye movements in four areas of interest of each picture (AOI): mouth, eyes, forehead, and nasolabial furrow. Pediatricians evaluated the intensity of pain with a verbal analogue score from 0 to 10 (0 = no pain; 10 = maximum pain). The number of pictures in which pediatricians fixed their gaze, the number of gaze fixations, and the total and average time of gaze fixations were compared among the AOI by analysis of variance (ANOVA). The visual-tracking parameters of the pictures' evaluations were also compared by ANOVA according to the pediatricians' perception of pain presence: moderate/severe (score = 6-10), mild (score = 3-5), and absent (score = 0-2). The association between the total time of gaze fixations in the AOI and pain perception was assessed by logistic regression. RESULTS: In the 20 newborn pictures, the mean number of gaze fixations was greater in the mouth, eyes, and forehead than in the nasolabial furrow. Also, the average total time of gaze fixations was greater in the mouth and forehead than in the nasolabial furrow. Controlling for the time of gaze fixation in the AOI, each additional second in the time of gaze fixation in the mouth (odds ratio [OR]: 1.26; 95% confidence interval [CI]: 1.08-1.46) and forehead (OR: 1.16; 95% CI: 1.02-1.33) was associated with an increase in the chance of moderate/severe pain presence in the neonatal facial picture. CONCLUSION: When challenged to say whether pain is present in pictures of newborn infants' faces, pediatricians fix their gaze preferably in the mouth. The longer duration of gaze fixation in the mouth and forehead is associated with an increase perception that moderate/severe pain is present. KEY POINTS: · Neonatal pain assessment is intrinsically subjective.. · Visual tracking identifies the focus of attention of individuals.. · Adults' gaze in neonates' mouth and forehead is associated with pain perception..
- Synergism between tribological parameters – “micro-abrasive concentration level”, “micro-abrasive particle type”, and “liquid type” of a micro-abrasive slurry composition on the micro-abrasive wear behaviour of Fe-30Al-6Cr (at.%) iron aluminide alloy(2023-07-15) DE PAULA, A. F. M.; BORGES, D. F. L.; DA SILVA F. C.; ROSSINO, L. S.; MANFRINATO, M. D.; VERMA, V.; LUNA-DOMINGUEZ, J. H.; MAGNABOSCO, R.; SCHON, C. G.; Ronaldo Câmara Cozza© 2023 Elsevier B.V.Observing the importance of intermetallic materials in mechanical and metallurgical applications, the present work investigates the micro-abrasive wear behaviour in a model–carbide reinforced iron aluminide system. Fe–30Al–6Cr (at.%) iron aluminide alloy with carbon additions “as cast” specimen was tested. Micrographs revealed a continuous network of eutectic chromium carbides at the interdendritic regions of the D03 ordered aluminide matrix. AISI 52100 bearing steel sphere of diameter 25.4 mm (1″) was used for wear tests as counter body. Micro-abrasive slurries were prepared with micro-abrasive particles of black silicon carbide – SiC or alumina – Al2O3, with distilled water or glycerin, in four possible combinations of materials ⇒ “Al2O3 + H2O distilled”, “Al2O3 + glycerin”, “SiC + H2O distilled” and “SiC + glycerin”. Further, keeping the normal force constant and together with different levels of micro-abrasive slurries compositions and sliding distances, a factorial experiment was designed. Result analysis showed that wear volume increased with an increase in micro-abrasive slurry concentration, independently of the type of micro-abrasive particle and liquid. However, the micro-abrasive slurries prepared with SiC and distilled water provided larger wear volumes than the volumes of wear reported under the micro-abrasive slurries formulated with Al2O3 and glycerin. The reason is attributed to the high hardness of SiC particles resulting in high abrasion, whereas the Al2O3 – glycerin slurry lubrication effect restricted high wear. Wear micrographs revealed a change in worn surface morphology from “grooving micro-abrasion” to “rolling micro-abrasion” due to an increase in sliding distance and micro-abrasive slurry concentration.
- Use of ball-cratering wear test and nanoscratching test to compare the wear resistance of homogeneous and functionally graded titanium nitride thin films(2023-01-05) CARNEIRO DA SILVA F.; DE MATOS MACEDO M.; COSTA MISCIONE J. M.; FONTANA, L. C.; SAGA J. C.; Ronaldo Câmara Cozza; SCHON C. G.© 2022 The Author(s).Homogeneous (HM) and functionally graded (FG) TiN thin films were produced by the grid-assisted magnetron sputtering (GAMS) technique. The joint use of ball-cratering micro-abrasive wear test (BCMA) and nanoscratching (NN) test was proposed and carried out to evaluate the wear resistance of TiN films. The results showed an increase of 33.3% wear resistance in the FG TiN thin film, when compared with the HM TiN thin film. This result was justified by the higher resistance to nucleation and propagation of cracks and higher level of adhesion to the substrate by the FG TiN thin film, validated through the NN tests.
- Assessment of different more-electric and hybrid-electric configurations for long-range multi-engine aircraft(2023-03-15) GIMENEZ, F. R.; Carlos Mady; HENRIQUES, I. B.© 2023 Elsevier LtdIn this study, the characteristics, penalties, gains, and challenges in the electrification and hybridization process for long-range aircraft were investigated. A system and mission analysis was conducted on thermodynamics and cost. A reference aircraft was compared with other more-electric and hybrid-electric versions of the same type. These latter versions may carry batteries to supply the aircraft system and/or engine. A state-of-the-art propulsion and system architecture were also implemented in these innovative aircraft. A full factorial analysis was conducted to vary the battery energy density and the hybridization ratio for the hybrid configurations. A typical mission profile was developed to match the boundary conditions in all cases. The hybrid powertrains were confirmed in our results as exhibiting superior behavior compared to those of the other cases. The least efficient hybrid configuration, which employed an intermediate battery choice, reduced fuel consumption by 10.7% in the conventional aircraft and by 1% in the battery-powered more-electric type. Moreover, both baseline models were surpassed by the worst intermediate-battery hybrid aircraft by 3.6% and 1% in terms of overall mission exergy efficiency. Considering the actual low density of batteries available on the market, long-range hybrid-electric aircraft will require substantial time to become viable.