bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Analysis of Evolutionary Methods in Topological Optimization of Truss Structures: Progressive Directional Selection versus Evolutionary Structural Optimization
Authors: Nayro Silva Noronha Cavalcante  , Márcio André Araújo Cavalcante  , Luiz Carlos Lima Véras
Published: January 2025

The main difference between evolutionary methods and traditional structural topological optimization methods is that the former may not always converge to an optimized solution and can be challenging to implement. This work presents two heuristic and evolutionary methods, which aim to analyze truss structures obtained by the topological optimization process using the PDS and ESO methods, employing a ground structure type structure as the initial design domain. The Progressive Directional Selection (PDS) method is based on selecting a certain number of elements, established by the user, that most contribute to supporting the loads applied in an initial design domain. The selection stages involve a progressive number of selection steps, each eliminating a certain number of less efficient elements. Convergence occurs when the selected elements are the same in a certain number of consecutive selection stages, also pre-established by the user. The Evolutionary Structural Optimization (ESO) method is a technique where elements that contribute less to supporting loads in an initial domain are removed through a rejection rate. If removing elements with the same rejection rate value is no longer possible, an evolution rate value can be added to remove more inefficient elements. ESO convergence is achieved when the rejection rate evolves to a user-established value. The optimized structures obtained by both methods efficiently support the applied loads. The PDS method stands out for reaching optimized truss structures with a specific number of elements that ESO cannot obtain, but the former stands out for its shorter processing time.
Design optimization via genetic algorithms of acessible Ferris Wheels
Authors: Eduardo Coelho Dos Santos  , Zenón José Guzmán Nuñez Del Prado  , Gino Bertollucci Colherinhas
Published: January 2025

In Brazil, systematic studies related to the design of amusement park equipment are still incipient. Essential normative references for these projects, such as NBR 15926-2 and ISO 17842-1 which deals with design and installation safety requirements, are often not effectively applied, increasing the risk of structural failures and neglecting stability and operational safety evaluation. Consequently, most of these equipment are imported, lacking national designs. The aim of this paper is to perform a preliminary analysis of the structural design of an accessible flexible Ferris wheel, evaluating safety coefficients through a parametric study of its geometry, including actions related to its operation, loading, and wind action. The structure modeling is conducted via Finite Element Method (FEM) using Ansys Mechanical APDL software using beam and mass elements. A routine implemented through MATLAB software communicates the input parameters and the modeled structure via FEM, allowing an easy alteration of the geometric variables, as well as the rectangular or square steel tube sections standardized by NBR-6591. Finally, a multi-objective optimization is implemented via Genetic Algorithms (GAs) with a fitness function aiming to maximize the safety coefficient and minimizing the mass. Optimal combinations are investigated and compared, proving the efficiency of this design methodology.
Dynamic model adjustment of a honeycomb sandwich panel using response surface methods and parametric optimization algorithms
Authors: Rodrigo Evangelista Aguiar de Souza  , Cássio Buss Mainardes  , Maura Angelica Milfont Shzu  , Sergio Henrique da Silva Carneiro
Published: January 2025

The aeronautical and aerospace industries have been evolving in technologies that improve the efficiency of their structures, where, in this context, sandwich panels with honeycomb cores are one of the frequently employed technologies in aircraft and nano satellites. This type of structure presents superior mechanical properties compared to traditional panels, as well as a low structural weight due to its porous core. However, they exhibit complex characteristics both geometrically and behaviorally, requiring the use of more sophisticated computational tools such as finite element analysis packages. Precise numerical models are required to allow for reliable analysis during the design process of aerospace structures. The most commonly employed approach is to create a numerical model and refine it through adjustments using experimental data. This study presents the modal numerical analysis of a sandwich panel with a honeycomb core using finite elements and proposes an adjustment of the obtained numerical model. The panel is composed of Aluminum 2024 skins and an Aluminum 5056 honeycomb core. This panel had its vibration modes and frequencies previously identified through experimental tests. Once the numerical and experimental values are compared, a numerical-experimental adjustment is proposed using the optimization algorithms NLPQL, MISQP, and Genetic, which are applied through two methodologies, with and without the use of a metamodel, where the metamodel is constructed using the kriging algorithm. The optimization problem was formulated considering the minimization of a function defined as the sum of squared differences between experimental and numerical frequencies. The ANSYS Workbench software package was utilized for the numerical modeling, which also provided the necessary optimization algorithms. The results demonstrate good agreement with the experimental data, and the numerical adjustments made using the optimization algorithms proved to be effective.
Evaluation of Optimization Algorithms for Calibration of Numerical Models of Engineering Structures
Authors: Thiago Artur Mendes de Souza  , Elcio Cassimiro Alves  , Giedre Alves Sirilo  , João Victor Fragoso Dias
Published: January 2025

In civil engineering, the finite element method (FEM) is used to simulate the behavior of buildings, bridges, and other structures. However, there are several uncertainties that make it difficult to obtain a representative computational model suitable for evaluation and monitoring of existing structures. To overcome this, the calibration of the numerical model based on experimentally obtained modal data is employed. This step allows for the updating of parameters that are difficult to obtain directly, in order to approximate the dynamic response of the computational model to that of the real structure. For this purpose, various algorithms can be employed, presenting differences in approach, effectiveness, and computational cost. This study aims to compare the performance of different optimization algorithms applied in the calibration of numerical models. To achieve this, the model of a structure will be established beforehand, with initial uncertainties represented by masked parameters; a set of modal parameters will be extracted, and then a new calibrated model will be developed through distinct optimization processes. The calibrated models will be compared with the initial model to evaluate their performance in predicting structural behavior, considering aspects such as accuracy in reproducing initially unknown parameters and the computational cost of each solution. Thus, it will be possible to enhance the calibration process by identifying the most appropriate algorithm.
Multi-objective structural optimization of a space truss considering geometric nonlinearity and global stability aspects
Authors: João Marcos de Paula Vieira  , Afonso Celso de Castro Lemonge  , Erica da Costa Reis Carvalho  , Patrícia Habib Hallak
Published: January 2025

The literature has broadly discussed developing and solving multi-objective structural optimization problems (MOSOPs) with two objectives. The conflicting objective functions commonly addressed are minimizing the structure's weight and maximum displacements. In this paper, the two objective functions considered are minimizing the weight and maximizing the first critical load factor related to the structure's global stability. The constraints are related to the maximum stresses in the bars, the maximum allowed nodal displacements, and the minimum value determined for the first natural frequency of vibration. The analyzed structure is a 25-bar truss. When defining the displacements and deformed configurations of the structure, a geometrically nonlinear analysis is applied using the arc-length method. This analysis allows the decision-maker to obtain more realistic and accurate values regarding the objective functions and constraints. The evolutionary algorithm used is the multi-objective meta-heuristic with iterative parameter distribution estimation (MM-IPDE). The Pareto fronts obtained in the proposed problems are presented, as it is possible to observe, for example, how the growth of the truss' weight causes increases in the first critical load factor. Finally, optimized solutions are extracted from the Pareto fronts.
Multiobjective Optimization of prestressed composite steel and concrete beam via non-dominated sorting genetic algorithm (NSGA)
Authors: Elcio Cassimiro Cassimiro  , Adenilcia Fernanda Grobério Calenzani  , Sayonara Maria de Moraes Pinheiro
Published: January 2025

The use of prestressing in steel beams and composite steel and concrete beams is still underexplored in the design of structures with large spans due to the lack of specific normative codes for this type of structural element. Studies involving optimization techniques for these types of structures are scarce in the literature, thus opening up a vast field of research to be explored. This study aims to propose the formulation of a multi-objective optimization problem for composite steel and concrete beams with external prestressing. The final cost of the beams, CO2 emissions from the materials used in their fabrication, and the maximization of the payload that the beam can support are considered minimization objectives. Constraints include the requirements for composite steel and concrete elements from NBR 8800:2008 and the prestressing provisions from NBR 6118:2021. The non-dominated sorting genetic algorithm (NSGA) from the Matlab package will be used to solve the optimization problem. Examples demonstrating the solution's effectiveness will be compared with examples from the literature, and Pareto frontiers will be evaluated to verify the best solutions for the proposed problems.
Optimal Design of Composite Floor Systems composed of Cellular Beams via Ant Colony Algorithm
Authors: Elcio Cassimiro Cassimiro  , Lucas DAmato Nitz  , Sayonara Maria de Moraes Pinheiro
Published: January 2025

The use of composite floor systems has been increasing in recent years, primarily with full-web beams, while other beam topologies, such as cellular beams, remain underutilized. The objective of this study is to propose a formulation for the optimal design of composite floor systems composed of cellular beams. The objective function will analyze the costs and final CO2 emissions of the floor. Technical prescriptions proposed in the literature will serve as constraints, as Brazilian standards lack clear guidelines for the design of cellular beams. To solve the optimization problem, the Ant Colony Algorithm (ACO) will be employed. A comparative analysis with solutions proposed in the literature for floors with solid beams will be conducted to assess the efficiency of the proposed solution for composite floors with cellular beams.
Optimal design of structures using metaheuristics and metamodeling
Authors: Erica da Costa Reis Carvalho  , João Marcos de Paula Vieira  , Patrícia Habib Hallak  , Afonso Celso de Castro Lemonge
Published: January 2025

Computation-intensive structural design optimization problems are common in engineering. The computation burden is often caused by expensive simulation models and becomes a problem in practice. To address such a challenge, metamodeling techniques are often chosen to improve the optimization efficiency. Metamodels, or surrogate models, are very popular methods and are considered a valuable tool to support a wide scope of activities in modern engineering design. The paper discusses strategies to obtain suitable metamodels to assess their quality concerning prediction, considering machine learning techniques used in the literature. A multi-objective structural optimization problem is used to illustrate the applicability of the approach, considering as objective functions the structures weight, and critical load factor concerning the structures global stability. The numerical results demonstrate the efficiency and computational advantages of the proposed methodology.
Optimization of materially nonlinear trusses subjected to dynamic loads
Authors: Elcio Cassimiro Cassimiro  , Marcos Antonio Campos Rodrigues  , Bárbara Scardini Domingues
Published: January 2025

The structural optimization of trusses has been extensively studied over the past few decades. However, investigations incorporating material nonlinearity are still relatively scarce. The objective of this study is to propose a formulation for optimizing spatial truss structures, considering the material nonlinearity of the structure under dynamic loading. To address this problem, the Particle Swarm Algorithm (PSO) integrated into the Ansys program will be utilized for nonlinear dynamic structural analysis. To validate the optimization approach, a problem from the literature, considering material nonlinearity, will be analyzed. Additionally, will be compared the results obtained from the structural optimization considering and neglecting the material nonlinearity. This comparison aims to assess the real impact of material nonlinearity on optimization results.
Strategies in Decision Making in a Multiobjective Context: Integration of DOE, NBI, and CFD in the Optimization of a Centrifugal Fan
Authors: Matheus Costa Pereira  , Tiago Martins de Azevedo  , Matheus Brendon Francisco  , Anderson Paulo de Paiva
Published: January 2025

Multiobjective optimization problems present significant challenges when attempting to balance conflicting variables simultaneously; furthermore, the creation of an adequate dataset can be a complex task. To address these challenges, an integrated approach is adopted, combining Design of Experiments (DOE) and Normal Boundary Intersection (NBI).DOE is employed to plan experiments in a balanced and economical manner, allowing for valuable information to be obtained with fewer resources. Subsequently, NBI is used to optimize multiple objectives simultaneously, creating an equispaced Pareto surface that defines an efficient boundary.To handle uncertainty in parameter estimates and analyze variable clustering, a confidence ellipse is constructed. This ellipse provides a visual representation of the uncertainty associated with estimates and assists in identifying patterns in the data.Once the efficient boundary with numerous results is obtained, the challenge arises of choosing the best solution among those available. For this purpose, Mahalanobis Distance (MD) is utilized, which are weighted Euclidean distances, taking into account the covariance of variables. This technique aids the decision-maker in selecting the most suitable solution.To demonstrate the effectiveness of integrating these techniques, a problem involving Computational Fluid Dynamics (CFD) is explored, encompassing an industrial centrifugal fan. In this scenario, conflicting variables include mass flow rate at the outlet and required torque, with four control variables: number of blades, blade inlet angle, blade outlet angle, and blade length.After identifying the best possible fan based on the smallest MD, the product is computationally replicated under optimal conditions, and the result is verified.This integrated approach combines techniques from DOE, CFD, and NBI that address all stages, from dataset creation to optimization and confirmation of results obtained, offering a comprehensive methodology for solving complex engineering problems.
A low-cost system for continuous dynamic monitoring and autonomous data analysis using the Internet of Things and Machine Learning
Authors: Bernardo Lopes Poncetti  , Dianelys Vega Ruiz  , Marcos Massao Futai
Published: January 2025

Structural health monitoring using the Internet of Things (IoT) is the latest tech-nique employed in the field of structural damage detection. Although conventional systems based on commercial sensors, such as piezoelectric accelerometers, pro-vide high accuracy, their high cost often limits their application. To address this is-sue, one possibility has been the development of strategies using low-cost sen-sors. However, there are several challenges to be addressed, such as the optimiza-tion of the low-cost devices to increase their reliability in reading and processing data, and the development of data storage and data transmission strategies, mainly for dynamic monitoring applications, which requires working with large amounts of data. In this regard, this paper presents the development of a low-cost SHM so-lution, which is able to collect, store, process and transmit vibration data to the cloud from an instrumented aluminum beam. For this purpose, a prototype is de-veloped using an ESP32 board, an MPU6050 triaxial accelerometer and a mi-croSD card. A completely low-cost system is adopted, where the data processing and availability of results to the final user is performed in the free version of ThingSpeak IoT platform from MathWorks. As a result, a fully automatic dynam-ic monitoring strategy able to collect, store and transmit raw vibration data to the cloud is developed. Then, the raw acceleration data is processed and analyzed in the cloud, where the Fast Fourier Transforms (FFT) are computed and visualized in quasi-real time.
Aspects of Identifying a Damaged Site of a Wind Turbine Blade Using Power Spectral Density (PSD) Signature Curves and Energy Correlation Referenced Distance
Authors: Horacio Duarte
Published: January 2025

The following procedure is based on the energy correlation distance applied to the PSD (power spectral density) signature curves. Each PSD curve is calculated from the measurements at a point in the structure. The energy correlation distance between a single PSD curve and the set of all PDS curves of the measurement mesh is a metric. This metric is called the energy correlation referenced distance. In this work, to increase the difference between a healthy site and a damaged site, frequency bands of PSD curves are used. Using the temperature compensation properties of the referenced distance, the results are computed for a wide range of temperatures and then an analysis is made considering the structural constraints. The data used comes from a composite wind turbine blade whose data is housed in a public repository.
Structural damage identification through machine learning approaches using FRFs
Authors: Dianelys Vega Ruiz  , Bernardo Lopes Poncetti  , Marcos Massao Futai
Published: January 2025

In this paper, experimental tests and numerical simulations are conducted to evaluate the performance of different models for structural damage identification and quantification. For this purpose, an aluminum beam in Laboratory conditions is utilized as a test structure. Firstly, impact tests are performed to identify the modal parameters and frequency response functions (FRFs) of the healthy structure. Then,different damages are induced in the beam by means of rectangular notches, and FRFs from each damage scenario are measured. Meanwhile, a simplified numerical model of finite elements of the beam is developed and calibrated with respect to experimental data. The calibrated model is used to generate a set of simulations representing the different damage scenarios induced experimentally. The damage is introduced in the numerical model by reducing the cross-sectional area. Normalized FRF amplitudes are used as the damage indexes. To increase the predictive capability of the models, uncertainties are introduced considering the FRF amplitudes as random variables. Afterward, different datasets are constructed and several well-established machine learning classifiers such as Decision Tree, SVM and KNN are trained to perform damage identification and quantification. Finally, experimental data measured on the damaged beam are used as input variables to evaluate the prediction capacity of the trained classifiers. Undamaged and damaged data are correctly classified by most of the classifiers. However, to quantify the degree of damage some shortcomings are found.
Geometric Nonlinear Analysis using the Two-cycle Method in Ftool
Authors: Rodrigo Bird Burgos  , Luiz Fernando Martha
Published: January 2025

With recent advances in design and material technology, increasingly slender structures are being conceived, which makes nonlinear analysis an important task for efficient and safe projects. Geometrically nonlinear problems are usually solved using the Finite Element Method (FEM) along with iterative numerical schemes, in which the structure response is directly influenced by the level of discretization and the nonlinear solution algorithm used. Thus, nonlinear analysis demands some experience from the analyst in terms of the parameters involved in the solution algorithms and structural behavior in general. To reduce the discretization dependence, exact solutions based on the deformed infinitesimal element equilibrium can be used as interpolation functions. To circumvent the difficulties in dealing with parameters related to the numerical methods, the two-cycle method can be used, since it is not dependent on load or displacement steps. The structural analysis software Ftool, widely used by Civil Engineers and students was adapted to perform two-cycle analyses employing frame elements based on solutions of the differential equations obtained from the deformed configuration. The results in terms of displacements and rotations for the examples studied are identical to the analytical solutions, showing that the combination of the two-cycle method with the exact element formulation is promising and can diminish the need for discretization and the use of complicated nonlinear solution algorithms.
Geometrically nonlinear truss analysis using Python's optimization libraries
Authors: Jorge Carvalho Costa  , Isabela Sena de Oliveira Cabral  , Eduardo Magalhães Vieira
Published: January 2025

This paper presents an efficient computational framework for analyzing trusses subject to geometric nonlinearities using Python common libraries for numerical optimization. Beginning with a brief discussion on truss kinematics and linear material behavior, we proceed to describe the deformed configuration of the truss and its internal energy based on nodal displacements. We then evaluate some numerical optimization libraries available to select the most suitable method for our problem, thus avoiding the explicit derivation of equilibrium equations and tangent matrices. The equilibrium of the truss is defined as the configuration with minimal potential energy and this is taken as the objective function of the optimization algorithm. Finally, we conclude with numerical examples comparing our approach with classical solutions based on a system of nonlinear equations. The proposed framework offers an interesting alternative for solving the nonlinear equilibrium problem, with particular potential for educational purposes and code prototyping. While our approach may not optimize computational runtime, it significantly streamlines coding time, thereby enhancing accessibility and usability in engineering applications.
Hydraulic Modeling of Water Distribution Networks: Hardy-Cross Method Implemented in Python
Authors: Thiago Rodrigues Santos  , José Antonio da Silva Neto  , Ariana Rosella Cervino  , Daysy Lira Oliveira Cavalcanti
Published: January 2025

Distribution network is a part of the water supply system that, formed by pipes and accessory parts, aims to provide potable water to consumers continuously with recommended quantity and pressure (TSUTIYA, 2006). However, due to the exponentially growing demand for potable water, the design of network layouts has become increasingly complex nowadays. In this regard, due to regional parameters such as topography and supply size, the use of meshed networks is feasible, in other words, networks that can supply a point through different paths due to their ring or block shape. Thus, this study aims to evaluate the performance of a meshed distribution network of a fictitious layout developed by undergraduate Civil Engineering students at the Federal University of Alagoas (UFAL) through system modeling in a Python program using the Hardy-Cross method. Furthermore, the effectiveness of the computational program was validated by comparing its results with those provided by the EPANET software. The methodology was based on the bibliographic review of issues related to solving meshed networks using the Hardy-Cross method, where a fictitious problem was modeled with parameters specified in NBR 12218/2017. Thus, this method was implemented in a computational program in Python language, and from this, the results related to the established layout were obtained. Additionally, the same layout was built in the EPANET software, and its results were used to validate the computational program. Therefore, it was possible to conclude that the computational program presented satisfactory results when compared to the EPANET software data, obtained due to recent performance advances in the Python language, which adds greater ease of use, result accuracy, modeling problem speed, and expands the possibilities of evaluating network performance. Finally, it was found that both modeling approaches are in accordance with the reference values established by TSUTIYA (2006) and recommended by NBR 12218/2017.
Implementing Steel Design in Educational Software: The Linear Elements Structure Model Program
Authors: Allan Pires Pitanga  , Luiz Fernando Martha  , Leonardo Carvalho Mesquita  , Ronald Junior Lemos Assunção  , Rafael Lopez Rangel  , Pedro Cortez Fetter Lopes
Published: January 2025

The Linear Elements Structure Model, or LESM for short, is a user-friendly, free-to-use, and open-source educational software for the structural analysis of models composed of linear elements. Aimed at aiding students, teachers, engineers, and architects to understand the behavior of structures better and improve their workflow, its intuitive and straightforward GUI (Graphical User Interface) allows a simple yet effective approach to modeling, running calculations of linear-elastic static and dynamic effects, and visualizing the internal stresses and strains in two-dimensional and three-dimensional trusses and frames. This paper expands upon the capabilities of LESM by detailing the implementation of steel design for bidimensional frames in compliance with the Brazilian steel structure design code, NBR8800:2008, within the current version of the software, building upon previous efforts to enhance LESM's functionality through object-oriented programming in the MATLAB environment. With the feature of steel design initially conceived as an extension for a prior version of the software, the LESM program has since been updated and reworked with more straightforward and quicker user interaction, a more optimized source code, and the addition of new features. By comparing past and current versions of the software and examining the source code of the steel design extension, it was possible to successfully integrate the steel design feature into the latest iteration of LESM, broadening the programs scope of use, both for the academic and industrial sectors in the field of analysis and design.
Interactive Modeling of NURBS for Isogeometric Analysis
Authors: João Carlos L. Peixoto  , Rafael L. Rangel  , Luiz F. Martha
Published: January 2025

Isogeometric Analysis (IGA) is a numerical analysis method for structures that arises with the proposal of unification between design and simulation, allowing the creation of computational models that preserve the exact geometry of the problem. This approach is possible by a class of mathematical functions called NURBS (Non-Uniform Rational B-Splines), widely used in CAD (Computer Aided Design) systems for modeling curves and surfaces. In isogeometric analysis, the same functions representing the geometry approximate the field variables. In this context, this work was developed to provide a tool within the scope of computational mechanics for two-dimensional isogeometric analysis of linear elasticity problems, including the steps of modeling, analysis, and visualization of results. The system consists of two software programs: FEMEP (Finite Element Method Educational Computer Program), developed in Python and responsible for the geometric modeling stage, and FEMOOLab (Finite Element Method Object Oriented Laboratory), a MATLAB software for analysis and display of results. The proposed tool features a graphical user interface (GUI) that allows intuitive visualization and manipulation of NURBS curves with advanced modeling features such as curve intersection and region recognition features that streamline and simplify the process. The open-source system allows collaboration and continuous development by the community of users and developers.
STONEHENGE  A toolbox for nonlinear vibration energy harvesting
Authors: Americo Barbosa da Cunha Junior  , João Pedro Norenberg  , João Victor Peterson  , Vinicius Gonçalves Lopes  , Roberto Luo  , Leonardo de la Roca  , Marcelo Pereira  , José Geraldo Telles Ribeiro
Published: January 2025

In this work, we present STONEHENGE - Suite for nonlinear analysis of energy harvesting systems, a comprehensive toolbox engineered to study nonlinear piezoelectric vibration energy harvesters. These harvesters can harness kinetic energy from the environment and convert it into electricity using the piezoelectric effect. By introducing nonlinearity through strategically placed magnets, their efficiency is enhanced across a wide frequency spectrum. However, it comes at the cost of increasing complexity in system dynamics. To investigate this complexity and comprehend the potential of nonlinear energy harvesting, the STONEHENGE library was created. It is tailored to analyze the harvesting performance and dynamic behavior of these systems and allows users to explore and characterize system dynamics across a diverse range of physical parameters and excitation conditions using advanced numerical simulations. The toolbox encompasses six key modules, (i) initial value problem, analysis of system behavior from initial conditions; (ii) dynamic animation: which provides visual representations of system dynamics, aiding in intuitive understanding and interpretation; (iii) nonlinear tools: equips users with tools to dissect and comprehend the nonlinear aspects of vibration harvesting systems, essential for comprehensive analysis; (iv) sensitivity analysis: facilitates the assessment of how system behavior responds to variations in parameters, offering insights into its robustness and performance under different conditions; (v) stochastic simulation: allows for the exploration of system behavior under stochastic excitation, crucial for understanding real-world operating conditions; (vi) chaos control: offers methods for mitigating chaotic behavior within the system, enhancing predictability and stability. Utilizing a bistable oscillator as a benchmark, STONEHENGE aims to serve as a valuable resource for the development and refinement of both existing and emerging nonlinear vibration-based energy harvesting systems. By providing a comprehensive toolkit for analysis and characterization, STONEHENGE seeks to catalyze advancements in this field, ushering in an era of more efficient and sustainable energy harvesting technologies. Moreover, this library was developed to be easily adaptable to different dynamic systems and can contribute to different application fields.
A study on the usage of magneto rheological elastomers for non-linear aeroelastic oscillations control
Authors: Henrique Edno Leoncini de Carvalho  , Reyolando Manoel Lopes Rebello da Fonseca Brasil
Published: January 2025

Magneto Rheological Elastomers (MRE) are composite intelligent materials, which can substantially change their viscoelastic properties due to their high magneto-sensitivity in response to different regimes of external magnetic field. Under the influence of a magnetic field, both storage shear and loss factor of MREs increase, this field-induced phenomenon is often referred to as the magnetorheological effect. The practical application of MR materials demonstrates great potential for several areas, as indicates the increasing number of patents registered in the last decade. This research is included in a line aimed to develop MRE devices for structural vibrations' control, exploring the magnetorheological effect and its capacity to promote gains in viscoelastic properties, thus enabling changes of relevant magnitudes in structural systems, such as the natural frequency and damping ratio. This adaptive behavior can be studied by the analysis of qualitative numerical simulations, this study proposes to investigate the effectiveness of MRE devices on wind induced aeroelastic oscillations (galloping equation), the results are obtained by the Multiple Scale Method and numerical integrations, showing a trajectory suppression on the phase-plane of limit cycles to focal points, as well as a three-fold change in the critical speed and alterations on the shape of the Hopfs bifurcation diagram.
Comparison of the performance of a cylindrical Hall thruster with different anode voltages via numerical simulations
Authors: Sergio Thadeu Tavares da Silva Junior  , Rodrigo Andres Miranda Cerda  , Sarah Gomes da Silva Paes da Costa  , Helbert de Oliveira Coelho Júnior
Published: January 2025

Plasma propulsion, or electric propulsion, arises from the need to explore deep space in a more economical and efficient manner. The cylindrical Hall Thruster (CHT) is an electric propulsion device that offers high propellant utilization and performance at smaller dimensions and lower power levels than traditional plasma propulsion devices. The reduced dimensions of the CHT operating at lower power levels make it an interesting option to provide propulsion of CubeSats and small satellites. The CHT consists of a channel with an annular anode through which neutral gas is injected. The neutral gas is then ionized by magnetized electrons injected from an external hollow cathode. The resulting plasma ions are ejected from the device due to the positive electrostatic potential at the anode, giving thrust. The aim of this work is to understand and study the plasma in the discharge channel of a CHT through numerical simulations. The numerical code describes the plasma with a hybrid model in which the electrons are treated as a fluid and the ions and neutral atoms as pseudo particles. The simulations were conducted for two different potential values at the anode, namely, 150 V and 300 V, representing different modes of operation. The results obtained with this simplified model allow to obtain an optimal configuration for a future prototype to be implemented at the Plasma Physics Laboratory at the University of Brasilia.
System identification of a lead-acid battery based on experimental data
Authors: Raphaela Carvalho Machado  , Pedro M. Gonçalves  , Hugo Nunes Ferraz  , Saulo Gómez  , David C. F. Zúñiga  , Jefferson Lima  , Teófilo Miguel de Souza  , Jose M. Balthazar  , Luiz Carlos Sandoval Góes
Published: January 2025

This paper aims to identify a battery model using experimental data obtained from the discharge of a lead-acid battery. In particular, obtaining a representative mathematical model for the system is important to accurately determine the electrical characteristics of the battery and analyze its discharge behavior during use. Additionally, the model is extremely useful for the design of the Battery Management System (BMS), which consists of an electronic circuit that manages the rechargeable batteries and at the same time protects the circuit from operating outside its safe operating area. Regarding the functioning of lead-acid batteries, although there are complex chemical reactions and laws from physics that can be employed to describe the system dynamics, mathematical models obtained from identification techniques can be an alternative to modeling and understanding their behavior. Even though there are simple models to more sophisticated models, the degree of complexity of the model will be determined by the application for which it will be used. In this sense, this work presents the identification of an electrical model for a lead-acid battery from data gathered. Jackey's model was adopted to represent the battery dynamics, since this model, in addition to having the parameters modeled as resistive and capacitive elements and being well suited to the experimental data, offers the advantage of not presenting a high level of complexity. Furthermore, it is intended to extend the methodology applied to obtain a Matlab/Simulink model that simulates the energy generation and storage system from a photovoltaic system. In this work, experimental data are sampled for different battery discharge rates using the Arduino. Then, the optimization tools of Matlab environment were used for system identification. The objective is to apply the optimization techniques to obtain the parameters of Jackey's model. Finally, according to the results obtained, the mathematical model identified is representative of the system, and, therefore, the tool is a viable alternative for the mathematical modeling of lead-acid batteries.
A micromechanical approach to effective elastic properties of fiber-reinforced fractured cementitious materials
Authors: Marcos Bressan Guimarães  , Cássio Barros de Aguiar  , Samir Maghous
Published: January 2025

A micromechanical model is formulated in this work to predict the effective elastic properties of fiber-reinforced fractured cementitious materials. Fractures refer to a region of small thickness, along which mechanical and physical properties of the material are degraded. Unlike cracks, fractures are discontinuities able to transfer stress and, therefore, can be regarded from a mechanical viewpoint as interfaces endowed with a specific behavior under normal and shear loading. The presence of fibers enhances the post-cracking strength of cementitious materials due to the bridging effect of the fibers and improves their ductility. The present work employs a micromechanical approach to formulate the homogenized elastic behavior of fiber-reinforced fractured cementitious materials. In the context of Eshelbys equivalent inclusion theory, the approach makes use of the Mori-Tanaka scheme to estimate the homogenized elastic moduli. Fractures and fibers are modeled as oblate and prolate spheroids endowed with appropriate elastic properties. Particular emphasis is given to the situation of a cementitious matrix reinforced by aligned or randomly distributed fibers with randomly distributed microfractures.
A preliminar study on RVE homogenization for phase-field multiscale analysis
Authors: Hugo Mouro Leão  , Eduarda Marques Ferreira  , Roque Luiz da Silva Pitangueira  , Lapo Gori
Published: January 2025

Despite the phenomenological approach presents excellent results in material behavior analysis, real-world materials are inherently heterogeneous. A material is considered heterogeneous when, at a particular observation scale, it becomes feasible to discern multiple mixture phases within it. This level of observation is commonly referred to as the microscale, where interactions between constituents occur, ultimately leading to the emergence of cracks.Modeling a material at the microscale begins with defining a Representative Volume Element (RVE), which is the smallest part of the material that is large enough to statistically represent the entire mixture. This ensures that other samples of the same size exhibit similar properties with minor variations. The analysis of the RVE leads to obtaining the effective properties of a portion of the material. That process is called homogenization.Modeling a RVE can be a challenging task, as it requires the use of highly refined meshes to accurately capture the geometric representation of all mixture components. Therefore, phase-field models present themselves as a suitable choice for this type of modeling, once due to the intrinsic features of its variational formulation, they already need refined meshes and do not present localization effects.Thus, the objective of this work is to model a heterogeneous RVE and obtain its homogenized properties. This homogenization of the material parameters is fundamental for the upscaling operation of multiscale analyses.All implementation were done in INSANE, an opensource software developed by the Engineering Structures Department (DEES) of Federal University of Minas Gerais (UFMG).
Parametric study of combined tensile and shear-frictional damage models on the simulation of mesoscopic compressive failure in concrete
Authors: Marcela Gimenes  , Andrei Felipe Villa dos Santos  , Isabel Fonseca Souza  , Osvaldo Luis Manzoli
Published: January 2025

One approach that provides a more realistic numerical prediction of concretes mechanical behavior is the use of a mesoscopic scale, considering the different phases of the composite. To represent the non-linear material behavior, appropriate constitutive models must be employed, such as non-linear elasticity, damage or plasticity, among others. A Mesh Fragmentation Technique that places high aspect ratio interface elements between the regular mesh elements, delineating the potential crack paths, has been employed to model the complex crack propagation process in quasi-brittle materials such as concrete. Recently, an extension of this technique introducing a two-layer condensed interface element has been proposed. This two-layer element allows to describe compressive failure as a combination of debonding (mode-I) and sliding (mode-II) cracking, so that each layer is respectively ruled by tensile and shear-frictional constitutive damage models.One advantage of the proposed model is that it requires a reduced number of material parameters: tensile strength, fracture energy, cohesion, friction angle and shear softening. A parametric study aiming to evaluate the role played by each one of the parameters on the mechanical behavior of concrete is presented. A series of mesoscale uniaxial compression tests is simulated and the obtained predictions are compared to the correspondent experimental results. The influence of each parameter is evaluated in terms of the resulting average stress-strain curve, as well as the qualitative aspect of the specimen failure, described by the cracking patterns. This parametric study contributes to determining which parameters are more influential in the combined material failure, providing insights for future structural members simulations using the proposed technique.
Finite prism approach for stability analysis of laminated glass fins
Authors: Luiz Antonio Taumaturgo Mororó  , Evandro Parente Junior  , Raimundo Calixto de Melo Neto
Published: January 2025

The use of laminated glass (LG) as a structural material for load-bearing components within buildings has been growing over the last decades. LG can be obtained by bonding two or more pieces of glass by means of polymeric interlayers (e.g., poly vinyl butyral  PVB). This building process gives LG elements a huge advantage over the same ones made of fully monolithic glass with respect to safety, since after breakage the fragments usually remain attached to the interlayer, reducing the risk of injuries. As LG members usually present a high slenderness, they are susceptible to flexural buckling under compression, requiring specific calculation methods and verification procedures in order to guarantee appropriate and safe structural performance. Compared to literature, this work presents a novel approach that is focused on the prediction of the elastic critical buckling load of LG columns without any lateral restraints at the tensioned edges. The buckling loads of LG columns have been determined using Finite Element Method, generally using shell elements, or analytical models. Usually, such approaches make use of the concept of effective thickness, in which the thickness of a monolithic element with equivalent bending properties in terms of stress and deflection is employed. However, the effective thickness approach is either difficult to apply or inaccurate. Therefore, this work presents an efficient and accurate approach to evaluate elastic critical buckling loads of LG columns applying Finite Prism Method (FPM). The accuracy of the proposed approach is assessed comparing the results obtained using solid finite element and analytical models for fully monolithic glass columns, as well as LG columns composed by multiple glass layers.
Geometrically nonlinear analysis of planar frame structures with positional finite element method
Authors: Antônio Vaz Eduardo Júnior  , Arthur Álax de Araújo Albuquerque  , Daniel de Lima Araújo
Published: January 2025

Problems in structural engineering involving geometric nonlinearity are widely studied from numerical and experimental perspectives. From the numerical modeling point of view, to investigate the resistance mechanisms that develop in structures when subjected to large displacements, a mathematical formulation capable of numerically representing the phenomena that occur during the nonlinear behavior is necessary. This work addresses problems of planar frame structures involving geometric nonlinearity with a formulation available in the literature of the Finite Element Method (FEM) based on positions and generalized vectors as degrees of freedom. In this formulation, nodal positions are used as degrees of freedom of the problem, and the Saint-Venant-Kirchhoff constitutive law for plane stress state is adopted. Unlike the FEM formulation for displacements, the positional formulation adopted requires strategies for connecting non-collinear finite elements, involving penalization techniques to satisfy boundary conditions. As detailed in the literature the connections between non-collinear elements are performed with uniaxial and flexural springs. The strain energies of the springs are calculated based on the nodal positions of the structure, and their contributions to the Hessian matrix and internal force vector of the structure are performed with a penalization technique. To validate the implementation developed the solutions of the positional FEM are compared to analytical and numerical solutions obtained by the finite element software DIANA FEA. In addition, parametric analyses varying the connections stiffness values are carried out to determine minimum stiffness values for the connection springs to allow the representation of the nonlinear equilibrium trajectory of planar frame structures.