Papers by Marco A . Luersen
DOAJ (DOAJ: Directory of Open Access Journals), Aug 1, 2013
Usually, electrical machines have a metallic cylinder made up of a compacted stack of thin metal ... more Usually, electrical machines have a metallic cylinder made up of a compacted stack of thin metal plates (referred as laminated core) assembled with an interference fit on the shaft. The laminated structure is required to improve the electrical performance of the machine and, besides adding inertia, also enhances the stiffness of the system. Inadequate characterization of this element may lead to errors when assessing the dynamic behavior of the rotor. The aim of this work was therefore to evaluate three beam models used to represent the laminated core of rotating electrical machines. The following finite element beam models are analysed: (i) an "equivalent diameter model", (ii) an "unbranched model" and (iii) a "branched model". To validate the numerical models, experiments are performed with nine different electrical rotors so that the first non-rotating natural frequencies and corresponding vibration modes in a free-free support condition are obtained experimentally. The models are evaluated by comparing the natural frequencies and corresponding vibration mode shapes obtained experimentally with those obtained numerically. Finally, a critical discussion of the behavior of the beam models studied is presented. The results show that for the majority of the rotors tested, the "branched model" is the most suitable
One of the requirements of diesel engines certification process is that the engine do not exceed ... more One of the requirements of diesel engines certification process is that the engine do not exceed the specific particulate emissions limit in cycle (_). To calculate the _ , a manual process is required. The total amount of mass impregnated in the particulate filter is obtained by weighting the filter on a balance after each test. Therefore, it is not possible to obtain it without human intervention. In order to allow test rigs to operate in automatic mode, without an operator conducting the tests, an automatic way of calculating _ is required. Thus, the aim of this work is to develop a _ prediction model that does not require human intervention. For this, a machine learning approach, based on the random forests algorithm, is used. Data collected from 2012 to 2019 from three test cells of 11 and 13 liters diesel engines of an automotive company, summing up 2500 valid test results, are used as input. This data are employed to train the algorithm and build a prediction model. The prediction model is then validated using another 72 validation tests results. The accuracy of the final model considering a confidence interval of 95% is ±3,00 mg/kWh for the European Transient Cycle, and ±1,96 mg/kWh for the European Stationary Cycle.
Revista iberoamericana de ingeniería mecánica, 2019
portuguesO uso de molas ortodonticas para o fechamento de espacos por meio da mecânica do arco se... more portuguesO uso de molas ortodonticas para o fechamento de espacos por meio da mecânica do arco segmenta-do vem se mostrando muito eficiente ao longo dos anos, sobretudo pelas alcas do tipo T-loop. Essas alcas sao feitas com fios metalicos de diversas seccoes e ligas. O presente estudo tem como objetivo principal analisar a influencia de diferentes seccoes transversais de fios na movimentacao dentaria, com o uso de alca de geometria T-loop, de titânio-molibdenio. Para as analises a alca foi modelada tridimensionalmente e foram efetuadas si-mulacoes pelo metodo dos elementos finitos tridimensionais para grandes deslocamentos. Observou-se que ha um aumento nos valores de forcas e momentos reativos sobre os pontos de apoio (dentes), bem como na rigidez da alca, devido ao aumento da seccao transversal do fio metalico. Em relacao ao sistema de forcas resultante, nao foi observada diferenca significativa para as seccoes consideradas uma vez que a relacao momento/forca (M/F), responsavel por influenciar os tipos de movimentos dentarios, permaneceu praticamente inalterada. O es-tudo apontou tambem que ha restricoes no uso de algumas seccoes transversais, em determinados valores de a-tivacao, uma vez que as forcas reativas encontradas ficam fora da zona ideal para emprego de forcas ortodonti-cas. EnglishThe use of orthodontic retraction springs for the correction of dental positions has been very effi-cient over the years, especially T-loop orthodontic springs. These springs are made with metallic wires of vari-ous cross-sections and alloys. The present study mains to analyze the influence of different cross-sections of wires in the dental movement, with the use of T-loop geometry of titanium-molybdenum (TiMo alloy). The de-vice was modeled three-dimensional and simulations were carried out by the finite element method for large displacements. It has been observed that there is an increase in the values of forces and moments, as well as in the stiffness of the spring, with the increase of the cross-section of the wire. Regarding tooth movement, no sig-nificant difference was observed in cross-sections because the moment/force ratio (M/F) remained practically unchanged. The study also pointed out that there are restrictions in the use of some cross-sections in certain ac-tivation values, since the forces magnitudes are outside the zone of ideal orthodontic forces used clinically
Ao Prof. Carlos Alberto de Campos Selke, pela prestativa e valiosa orientação deste trabalho, pel... more Ao Prof. Carlos Alberto de Campos Selke, pela prestativa e valiosa orientação deste trabalho, pela formação acadêmica, pela amizade e pelas lições de vida transmitidas.
ABSTRACT http://www.emse.fr/~leriche/Giens03_slides_monofin6b.ppt
Proceedings of the ... International Congress of Mechanical Engineering, 2015
Computer systems science and engineering, 2022
Revista Dental Press de Ortodontia e Ortopedia Facial, Jun 1, 2008
As alças de retração ortodôntica são comumente empregadas em sistema Edgewise por meio de uma abo... more As alças de retração ortodôntica são comumente empregadas em sistema Edgewise por meio de uma abordagem seccional (ex.: retração de caninos) ou por meio de uma abordagem segmentada (ex.: retração dos dentes anteriores em conjunto). Estas alças podem modular a demanda de ancoragem, dependendo dos objetivos impostos pelo plano de tratamento. Neste trabalho são discutidas as propriedades mecânicas relacionadas ao projeto de alças de retração ortodôntica, o sistema de forças decorrente de sua conformação geométrica e ativação, e os métodos empregados para testálas. Dentre as técnicas utilizadas na análise de uma alça, o Método dos Elementos Finitos (MEF) merece destaque. Embora seja baseado em modelos matemáticos, é uma ferramenta eficaz e não onerosa para a simulação computacional de um protótipo, podendo-se assim avaliá-lo antes de sua construção física. Já os métodos experimentais se aproximam mais da condição real, porém com custo mais elevado. A utilização em diferentes estágios de ambos os métodos é aconselhável para um melhor desenvolvimento e caracterização dos protótipos. Palavras-chave: Alças ortodônticas. Propriedades mecânicas. Testes mecânicos. Unidade de ancoragem.
Civil-comp proceedings, May 26, 2009
One of the fundamental difficulties in engineering design is the multiplicity of local solutions.... more One of the fundamental difficulties in engineering design is the multiplicity of local solutions. This has triggered great efforts to develop global search algorithms. Globality, however, often has a prohibitively high numerical cost for real problems. A fixed cost local search, which sequentially becomes global is developed. Globalization is achieved by probabilistic restart. A spatial probability of starting a local search is built based on past searches. An improved Nelder-Mead algorithm makes the local optimizer. It accounts for variable bounds. It is additionally made more robust by reinitializing degenerated simplexes. The resulting method, called Globalized Bounded Nelder-Mead (GBNM) algorithm, is particularly adapted to tackle multimodal, discontinuous optimization problems, for which it is uncertain that a global optimization can be afforded. Different strategies for restarting the local search are discussed. Numerical experiments are given on analytical test functions and composite laminate design problems. The GBNM method compares favorably to an evolutionary algorithm, both in terms of numerical cost and accuracy.
Orthodontic Journal of Nepal, Aug 15, 2022
To verify the literature concerning the mechanical properties, measuring methods and the resultan... more To verify the literature concerning the mechanical properties, measuring methods and the resultant force system developed by closing loops (CL). The effectiveness of a certain CL is related to its geometry and the nature of the wire material. To obtain the necessary performance CL must work in the elastic range and be geometrically configured to express an adequate force system, which is the result of compensatory gable bends and preactivation. It was performed a literature search in MEDLINE from 1974 to 2014 using search for "orthodontic AND retraction AND springs" and "orthodontic AND closing AND loops". From the 147 papers resulted from Pubmed, 50 were chosen. Overall, many works seek not only improve the knowledge about the force system, but also a better understanding of their mechanical behavior. FEM, Holographic and Photoelastic studies, are tests commonly used before testing them experimentally. Wire material and the cross-section show a great influence in the choice of the geometric variables because the modulus of elasticity (E), modulus of resiliency (R) and the moment of inertia (I). Experimental tests should be preceded by numerical methods because the latter idealize a particular setting, and allows modifying variables.
Revista Brasileira de Engenharia Biomédica, Sep 1, 2014
The purpose of this study was to analyze the force system, moment-force ratios (M/F) and von Mise... more The purpose of this study was to analyze the force system, moment-force ratios (M/F) and von Mises stresses in an orthodontic delta spring using a 3D fi nite element model. The M/F ratio produced by an orthodontic spring is related to the different types of tooth movement that are likely to occur in the sagittal and occlusal planes. Methods: Analyses were performed using a 3D fi nite element model, and a data acquisition system was used to validate the numerical results. Results: Reactive forces between 0.0 and 2.0 N were observed along the x-axis, while null values were observed along the y-and z-axes. The maximum activation that ensured geometric stability and mechanical stresses below the elastic limit of the material was 10.0 mm. Conclusions: The results indicate that a delta spring can provide (i) uncontrolled tipping for activation of less than 1.0 mm; (ii) controlled counterclockwise tipping for activation between 1.0 and 4.5 mm; (iii) translation for activation between 4.5 and 5.0 mm; and (iv) controlled clockwise tipping in the sagittal plane for activation between 5.0 and 10.0 mm. No tooth movement was observed in the occlusal plane for the M/F ratios observed.
Tecnologia em Metalurgia, Materiais e Mineração, 2022
ADIs are very versatile materials and can provide high performance in situations involving fatigu... more ADIs are very versatile materials and can provide high performance in situations involving fatigue and wear. To understand the effect of graphite nodules on fatigue strength of ADIs, an interesting way of studying are the numerical analyzes through the Finite Element Method (FEM). UTFPR in partnership with TUPY S.A., especially under the supervision of Prof. Dr. Wilson L. Guesser, has carried out several studies via FEM in order to generate enough interesting knowledge, both for the foundry company and for the end user of ADI. From the results of these studies, it was found that, in general, although smaller graphite nodules have a slight tendency to nucleate cracks more quickly, their characteristics of relieving stresses and generating a branched mesh of interconnected cracks, which absorb energy at the crack tips, makes ADI with small nodules becomes a very competitive material in gear manufacturing.
Structural and Multidisciplinary Optimization, Sep 8, 2017
The paper deals with the multi-objective optimization problems of laminated composite beam struct... more The paper deals with the multi-objective optimization problems of laminated composite beam structures. The objective function is to minimize the weight of the whole laminated composite beam and maximize the natural frequency. In particular, the simultaneous use of all the design variables such as fiber volume fractions, thickness and fiber orientation angles of layers is conducted, in which the fiber volume fractions are taken as continuous design variables with the constraint on manufacturing process while the thickness and fiber orientation angles are considered as discrete variables. The beam structure is subject to the constraint in the natural frequency which must be greater than or equal to a predetermined frequency. For free vibration analysis of the structure, the finite element method is used with the two-node Bernoulli-Euler beam element. For solving the multi-objective optimization problem, the nondominated sorting genetic algorithm II (NSGA-II) is employed. The reliability and effectiveness of the proposed approach are demonstrated through three numerical examples by comparing the current results with those of previous studies in the literature.
Dental Press Journal of Orthodontics, Aug 1, 2020
Objective: To perform a numerical simulation using FEM to study the von Mises stresses on Mushroo... more Objective: To perform a numerical simulation using FEM to study the von Mises stresses on Mushroom archwires. Methods: Mushroom archwires made of titanium-molybdenum alloy with 0.017 x 0.025-in cross-section were used in this study. A YS of 1240 MPa and a Young's modulus of 69 GPa were adopted. The archwire was modeled in Autodesk Inventor software and its behavior was simulated using the finite element code Ansys Workbench (Swanson Analysis Systems, Houston, Pennsylvania, USA). A large displacement simulation was used for non-linear analysis. The archwires were deformed in their extremities with 0° and 45°, and activated by their vertical extremities separated at 4.0 or 5.0 mm. Results: Tensions revealed a maximum of 1158 MPa at the whole part of the loop at 5.0mm of activation, except in a very small area situated at the top of the loop, in which a maximum of 1324 Mpa was found. Conclusions: Mushroom loops are capable to produce tension levels in an elastic range and could be safely activated up to 5.0mm.
Cmes-computer Modeling in Engineering & Sciences, Oct 26, 2018
This paper describes a study of the effects of graphite nodule characteristics on a subsurface cr... more This paper describes a study of the effects of graphite nodule characteristics on a subsurface crack in austempered ductile iron (ADI). A representative specimen of ADI, subjected to sliding contact load, is modeled using finite elements aiming to obtain the shear stress intensity factor (K II). The parameters varied were (i) the nodule diameter (two different values were considered), (ii) the distance between the nodule and the tip of the crack and (iii) the position of the load relative to the tip of the crack. The results of the numerical simulations show that the smaller diameter nodule has a larger influence on K II , suggesting a higher contact fatigue crack propagation rate in the material with the smaller nodule. These results are the opposite of those observed in experimental studies and would appear to indicate that other factors should be also considered to ensure realistic estimates of the contact fatigue strength of ADI.
Biomedical Engineering: Applications, Basis and Communications, Jun 1, 2023
Objective: To perform an experimental-numerical analysis to study the influence of the interbrack... more Objective: To perform an experimental-numerical analysis to study the influence of the interbracket distance (IBD) on the spring’s mechanical behavior and on the resulting force system during space closure in the segmented arch technique (SAT). Material and Methods: Twenty delta springs (DSs) made of beta-titanium alloy, [Formula: see text] inch, were tested on a platform transducer. A Young’s modulus ([Formula: see text] of 69 GPa ([Formula: see text] psi) and Yield’s strength ([Formula: see text] of 1240 MPa ([Formula: see text] psi) were used. The springs were activated considering different IBDs. The spring was modeled in autodesk Inventor software and its behavior was simulated using the finite element (FE) code Ansys Workbench. Results: The ANOVA showed a significant difference in the studied variables with a reliability of over 95% (only for the activation variable there was an effect upon the horizontal forces (Fx). The Tukey HSD and the Games–Howell post hoc multiple comparisons tests were applied to identify differences between the treatments for heterogeneous variances. Conclusions: The IBDs do not significantly affect the force system during space closure, even though there was an increase in the Mz/Fx ratio as spring deactivates. Activation can cause a statistically significant effect on the force system even though the force showed safe levels. At 4[Formula: see text]mm activation (19[Formula: see text]mm IBD), the spring wire starts yielding, i.e. plastic deformation occurs near the anterior attachment due to the shorter IBD.
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Papers by Marco A . Luersen