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Agora exibindo 1 - 20 de 190

Avaliação Mecânica e Determinação de Parâmetros na Colocação da Haste de HARRINGTON
(1985) DELIJAICOV, Sergio
Silício: Abundante, eclético, sofisticado
(2004-01-04) PAPALEO, R.
Design of robust controllers with time domain specifications Projeto de controladores robustos com especificações temporais
(2005) Leonardi F.; Da Cruz J.J.
The robust design of compensators with time domain specifications aiming setpoint tracking and disturbance rejection is discussed in this paper from a perspective of loop shaping. The constraints to provide robust disturbance rejection are derived as functions of reference models, which contain the associated time domain specifications. It is shown that the larger is the distance between the nominal plant model and the reference models to be followed the more restrictive the design constraints will be. The problems can be posed as model matching compensators and the proposed procedure may reduce the conservativeness normally associated with their design. The plant model is assumed subject to unstructured uncertainties and the design specifications are written in the usual form of loop shape constraints. Hence techniques like H∞ and LQG/LTR can be applied as design tools. In order to illustrate the use of the proposed methodology we consider a multivariable mixture tank as an example.
Phenomenological model of particulate matter emission from direct injection diesel engines
(2005-07-05) ARGACHOY, C.; PIMENTA, A. P.
A new phenomenological model is introduced by applying established conceptual models for direct injection combustion to develop a mathematical description of events. The model has the capability to predict particulate mass output, as well as a particulate mass history over a single combustion event. The model was developed in a Matlab-Simulink environment to promote modularity. Results of particulate mass output from single cylinder laboratory engine, and six-cylinder vehicular engine were used to determine the validity of the predictions made. Although predicted values do not perfectly match measured values, there is certainly reasonable agreement. Copyright © 2005 by ABCM.
Superficial integrity analysis in a super duplex stainless steel after turning
(2006) BORDINASSI, Éd Cláudio; STIPKOVIC FILHO, Marco; BATALHA, Gilmar Ferreira; DELIJAICOV, Sergio; Nelson Batista
Comparação entre ferramentas para furação de polímeros reforçados por fibra de vidro
(2006-04-05) BATALHA, G. F.; STIPKOVIC FILHO, M.; Sergio Delijaicov; Ed Claudio Bordinassi
Para obter furos de boa qualidade em matrizes termofixas reforçadas com fibra de vidro, deve-se reduzir a força axial e o torque durante a furação. O estudo experimental relatado neste artigo avalia o desempenho e aponta a influência de quatro tipos de ferramentas (brocas helicoidais de aço rápido, serra de copo comum, serra de copo diamantada e trepanadora com insertos de metal duro) sobre estes parâmetros. Com base em um planejamento estatístico dos experimentos e na análise de variância, é possível avaliar esses fatores individualmente, seus efeitos de interação e os respectivos níveis de significância.
Multivarible robust control with time-domain specifications: Servo and regulator problems
(2007) Leonardi F.; Da Cruz J.J.; Bittar A.
The robust design of compensators and the input scaling aiming setpoint tracking and disturbance rejection with time-domain specifications are presented from a perspective of loop-shaping. Since there is not an explicit relationship between loop-shaping and time-domain specifications, the latter are indirectly taken into account by forcing the plant output to follow the output of a reference model. The design specifications are written in form of loop-shape constraints. Hence, techniques like H∞ can be applied. In order to discuss the frequency dependence of the design constraints, an electromagnetic levitation suspension vehicle prototype and a multivariable mixture tank are considered. © Springer-Verlag 2007.
Residual stresses modelling in hard turning and its correlation with the cutting forces
(2007) DELIJAICOV, Sergio; AGUIAR, João Batista de; BORDINASSI, Éd Cláudio; BATALHA, Gilmar Ferreira; STIPKOVIC FILHO, Marco
Mutually connected phase-locked loop networks: Dynamical models and design parameters
(2008) Orsatti F. M.; Carareto R.; Piqueira J. R. C.
Distribution of timing signals is an essential factor for the development of digital systems for telecommunication networks, integrated circuits and manufacturing automation. Originally, this distribution was implemented by using the master-slave architecture with a precise master clock generator sending signals to phase-locked loops (PLL) working as slave oscillators. Nowadays, wireless networks with dynamical connectivity and the increase in size and operation frequency of the integrated circuits suggest that the distribution of clock signals could be more efficient if mutually connected architectures were used. Here, mutually connected PLL networks are studied and conditions for synchronous states existence are analytically derived, depending on individual node parameters and network connectivity, considering that the nodes are nonlinear oscillators with nonlinear coupling conditions. An expression for the network synchronisation frequency is obtained. The lock-in range and the transmission error bounds are analysed providing hints to the design of this kind of clock distribution system. © 2008 The Institution of Engineering and Technology.
Surface integrity analysis in the super duplex stainless steel ASTM-A890 after machining
(2008) Bordinassi E.C.; Stipkovic M.F.; Batalha G.F.; Delijaicov S.; De Lima N.B.
The purpose of this paper was to study the main effects of the turning in the superficial integrity of the duplex stainless steel ASTM A890-6A. The tests were conducted on a turning centre with carbide tools and the main entrances variables were: tool material class, feed rate, cutting depth, cutting speed and cutting fluid utilisation. The answers were analysed: microstructural analysis by optical microscopy and x-ray diffraction, cutting forces measurements by a piezoelectric dynamometer, surface roughness, residual stress by x-ray diffraction technique and the microhardness measurements. The results do not show any changes in the micro structural of the material, even when the greater cutting parameters were used. The smaller feed rate (0.1 mm/v), smaller cutting speed (110 m/min) and the greater cutting depth (0.5 mm) provided the smaller values for the tensile residual stress, the smaller surface roughness and the greater microhardness. Copyright © 2008 Inderscience Enterprises Ltd.
Removing Eddy-Current probe wobble noise from steam generator tubes testing using Wavelet Transform
(2008-09-05) Lopez L. A. N. M.; Ting D.K.S.; Upadhyaya B.R.
One of the most important nondestructive evaluation (NDE) applied to steam generator tubes inspection is the electromagnetic Eddy-Current testing (ECT). The signals generated in this NDE, in general, contain many noises which make difficult the interpretation and analysis of ECT signals. One of the noises present in the signals is the probe wobble noise, which is caused by the existing slack between the probe and the tube walls. In this work, Wavelet Transform (WT) is used in the probe wobble de-noising. WT is a relatively recent mathematical tool, which allows local analysis of non-stationary signals such as ECT signals. This is a great advantage of WT when compared with other analysis tools such as Fourier Transform. However, using WT involves wavelets and coefficients' selection as well as choosing the number of decomposition level needed. This work presents a probe wobble de-noising method when used in conjunction with the traditional ECT evaluation. Comparative results using several WT applied to Eddy-Current signals are presented in a reliable way, in other words, without loss of inherent defect information. A stainless steel tube, with two artificial defects generated by electro-erosion, was inspected by a ZETEC MIZ-17ET ECT equipment. The signals were de-noised through several different WT and the results are presented. The method offers good results and is a promising method because it allows for the removal of Eddy-Current signals' probe wobble effect without loss of essential signal information. © 2007 Elsevier Ltd. All rights reserved.
A low-cost anthropometric walking robot for reproducing gait lab data
(2008-12-05) Da Silva Santana R.E.; De Toledo Fleury A.; Menegaldo L.L.
Human gait analysis is one of the resources that may be used in the study and treatment of pathologies of the locomotive system. This paper deals with the modelling and control aspects of the design, construction and testing of a biped walking robot conceived to, in limited extents, reproduce the human gait. Robot dimensions have been chosen in order to guarantee anthropomorphic proportions and then to help health professionals in gait studies. The robot has been assembled with low-cost components and can reproduce, in an assisted way, real-gait patterns generated from data previously acquired in gait laboratories. Part of the simulated and experimental results are addressed to demonstrate the ability of the biped robot in reproducing normal and pathological human gait.
Reachability of the synchronous state in a mutually connected PLL network
(2009) CARARETO, R.; ORSATTI, F. M.; PIQUEIRA, J. R. C.
Second-order phase locked loops (PLLs) are devices that are able to provide synchronization between the nodes in a network even under severe quality restrictions in the signal propagation. Consequently, they are widely used in telecommunication and control. Conventional master-slave (M-S) clock-distribution systems are being replaced by mutually connected (MC) ones due to their good potential to be used in new types of application such as wireless sensor networks, distributed computation and communication systems. Here, by using an analytical reasoning, a nonlinear algebraic system of equations is proposed to establish the existence conditions for the synchronous state in an MC PLL network. Numerical experiments confirm the analytical results and provide ideas about how the network parameters affect the reachability of the synchronous state. The phase-difference oscillation amplitudes are related to the node parameters helping to design PLL neural networks. Furthermore, estimation of the acquisition time depending on the node parameters allows the performance evaluation of time distribution systems and neural networks based on phase-locked techniques. © 2008 Elsevier GmbH. All rights reserved.
Effects of weld strength mismatch on J and CTOD estimation procedure for SE(B) specimens
(2009) Donato G.H.B.; Magnabosco R.; Ruggieri C.
This work examines the effect of weld strength mismatch on fracture toughness measurements defined by J and CTOD fracture parameters using single edge notch bend (SE(B)) specimens. A central objective of the present study is to enlarge on previous developments of J and CTOD estimation procedures for welded bend specimens based upon plastic eta factors (η) and plastic rotational factors (rp). Very detailed non-linear finite element analyses for plane-strain models of standard SE(B) fracture specimens with a notch located at the center of square groove welds and in the heat affected zone provide the evolution of load with increased crack mouth opening displacement required for the estimation procedure. One key result emerging from the analyses is that levels of weld strength mismatch within the range ±20% mismatch do not affect significantly J and CTOD estimation expressions applicable to homogeneous materials, particularly for deeply cracked fracture specimens with relatively large weld grooves. The present study provides additional understanding on the effect of weld strength mismatch on J and CTOD toughness measurements while, at the same time, adding a fairly extensive body of results to determine parameters J and CTOD for different materials using bend specimens with varying geometries and mismatch levels. © Springer Science+Business Media B.V. 2009.
Optimized network structure for full-synchronization
(2009-06-05) Carareto R.; Orsatti F. M.; Piqueira J.R.C.
A network of Kuramoto oscillators with different natural frequencies is optimized for enhanced synchronizability. All node inputs are normalized by the node connectivity and some important properties of the network structure are determined in this case: (i) optimized networks present a strong anti-correlation between natural frequencies of adjacent nodes; (ii) this anti-correlation should be as high as possible since the average path length between nodes is maintained as small as in random networks; and (iii) high anti-correlation is obtained without any relation between nodes natural frequencies and the degree of connectivity. We also propose a network construction model with which it is shown that high anti-correlation and small average paths may be achieved by randomly rewiring a fraction of the links of a totally anti-correlated network, and that these networks present optimal synchronization properties. © 2008 Elsevier B.V. All rights reserved.
A transient three-dimensional heat transfer model of the human body
(2009-08-05) FERREIRA, M. S.; YANAGIHARA, J. I.
The objective of this work is to develop an improved model of the human thermal system. The features included are important to solve real problems: 3D heat conduction, the use of elliptical cylinders to adequately approximate body geometry, the careful representation of tissues and important organs, and the flexibility of the computational implementation. Focus is on the passive system, which is composed by 15 cylindrical elements and it includes heat transfer between large arteries and veins. The results of thermal neutrality and transient simulations are in excellent agreement with experimental data, indicating that the model represents adequately the behavior of the human thermal system. © 2009 Elsevier Ltd. All rights reserved.
Application of Mulltiple Regression and Neural Networks to Synthesize a Model for Peen Forming Process Planning
(2010) DELIJAICOV, Sergio; FLEURY, A. T.; MARTINS, F. P. R.
Surface integrity and residual stresses analysis by strain gages after hard turning process of case hardened steel aisi 8620
(2010) Farias A.; Delijaicov S.; De Mello J.D.B.; Filho M.S.; Batalha G.F.
This work aims an analysis on the functional surface integrity resulting from turning mechanical components manufactured from case hardened steel AISI 8620 with 1 millimeter average layer depth and hardness of 58-62HRC. A cBN tool with PVD coat and Wiper geometry-edge was used for continuous turning of hardened steel, the cutting conditions (Vc [m/min] and f in [mm/rev]) used were concerned to reflect large running production of mechanical components. © (2010) Trans Tech Publications.
Influence of Tempering Temperature in Wear of AISI T15 HSS Tools Produced by HIP and Liquid Phase Vacuum Sintering
(2010) LIMA, E. P. R.; NEVES, M. D. M.; DELIJAICOV, Sergio; AMBROZIO FILHO, Francisco
Improved model to predict machined surface roughness based on the cutting vibrations signal during hard turning
(2010) DELIJAICOV, Sergio; LEONARDI, Fabrizio; BORDINASSI, Éd Cláudio; BATALHA, Gilmar Ferreira

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