Postdoctoral Researchers
Rubens Gonçalves Salsa Junior
Abstract: This research proposal aims to study the attenuation of structural vibration and irradiated noise of reinforced panel of aeronautical interest with control inspired on electro-mechanical methamaterial methodologies. A challenge in the acoustic/elastic metamaterials research field is the development of the next generation of structures with adaptive and self-regulating dispersion properties without requiring structural modifications. The introduction of shunted piezoelectric materials into metastructures has the potential to provide adaptive properties by adjusting different electrical circuit parameters. The tunable characteristics of the shunted piezoelectric material allow the formation of bandgaps over a desired frequency range. Although current smart metamaterials present some level of tunability, many scientific and technological challenges remain and are expected to be tackled in this project, such as broadening the subwavelength bandgaps and assessment and exploitation of variability and uncertainties in the design and construction of metastructures. The research will be conducted at the Aeronautics Institute of Technology (ITA).
Project Title: Design and Evaluation of Piezoelectric Periodic Structures for Noise and Vibration Control of Panels
Supervisor: Domingos Alves Rade
Fapesp Grant: 2020/06022-0
Abstract: Acoustic metamaterials (AMMs) are nowadays a promising means for overcoming heavy and expensive sound isolation designs. Unusual low-frequency sound transmission loss (STL) properties are shown to come with lattices of substructures, arranged onto stiffer and lightweight primary structures (thus resulting in an AMM), which make the AMMs to be ideal for vibroacoustic isolation applications that impose mass addition constraints. Each array unit can be devised for either causing impedance variations in the material (Bragg scattering) or as linear resonators (mechanical or electromechanical absorbers). Yet the use and effects of nonlinear absorbers for realizing AAMs are research challenges that have not been investigated. This research project contributes to the development of AMMs by deepening on the study of nonlinear energy sink (NES) lattices, realized in the form of piezoelectric patches shunted by nonlinear electrical circuits. When coupled to a linear oscillator (e.g. a primary mechanical structure), NES systems are shown to act as dynamic absorbers that feature enhanced operation bandwidths. This property, together with their demonstrated capability in kinetic energy harvesting, make the NES concept to be attractive in the design of AMMs. With the aid of numerical studies that address the behavior and implications on the periodicity or quasi-periodicity of the AMM, number of NES-based cells in the lattice, as well as on the influence of uncertainties that arise from the actual materials and manufacturing methods, one- and/or two-dimensional host structures are targeted for the implementation of the obtained lattices. The capability of AMMs in kinetic energy harvesting is also set as a goal in this research project, based on the premise of improving the activation energy property of the NES-based cells as a function of the lattice topology. In this manner, this research project aims at proposing a numerical framework for designing AMMs featuring improved broadband STL properties and the capability for supplying usable electric energy, with corresponding validations through real-world experiments.
Jaime Alberto Mosquera Sánchez
Project Title: Control and energy harvesting from low-frequency vibro-acoustic disturbances with smart metastructures
Supervisor: Carlos De Marqui Junior
Fapesp Grant: 2018/14546-9
Abstract: Mechanical metamaterials have been extensively explored due to their extraordinary properties that allow vibration and acoustic attenuation as well as wave manipulation. The metamaterial term is nowadays employed to designate rationally designed and tailored periodic artificial materials with physical characteristics not found in nature. The presence of a band gap, a frequency range in which vibration disturbances will not propagate through the structure, is a key feature of metamaterials. Band gaps pave the way to create acoustic and vibration barriers at low frequency, seismic shielding, acoustic diode, two-dimensional waveguides and topological insulators. Usually, periodic structures present fixed dynamic behavior after the unit cell designing. Hence, their working frequency range or even their functionality would be only modified with a new design and a new structure fabrication. The periodic structures capabilities could be expressively expanded by tailoring or by reconfiguring the unit cell properties, resulting in tunable band gaps and hence, programmable phononic crystals and metamaterials. Programmable periodic structures can reveals extraordinary potentialities and versatility that cannot be achieved by their passive counterparts. Therefore, this research project aims to investigate smart and programmable phononic crystals and metamaterials to attenuate sound and vibration as well as to manipulate mechanical waves in a more efficient and versatile way. The wave propagation in periodic structures is a rich and dynamic research area with a wide range of open topics that have high potential to solve old engineering problems, to create new technologies and to impact our every-day-life.
Danilo Beli
Project Title: Manipulating Elastic Waves Using Topological Modes
Supervisor: Carlos De Marqui Junior
Fapesp Grant: 2018/18774-6
Abstract: This project will design the nonlinear periodic structure and performing experimental tests, aiming at achieving stop-bands at frequencies <100 Hz. The aims of the experiments are to validate the theoretical predictions made from the theoretical models, to investigate the practical issues in realising nonlinear periodic structures, and to determine their practical limitations in terms of the attenuation of vibration transmission. The researcher may also perform some theoretical work in conjunction with the doctoral student. This project is scheduled to be carried out in two years.
Vinicius Germanos Cleante
Project Title: Experimental Analysis of Nonlinear Periodic Structures
Supervisors: Michael J. Brennan / Paulo J. Paupitz Gonçalves
Fapesp Grant: 2020/00659-6
Metamaterials have gained attention in the recent years due to their capacity to achieve behaviour not encountered in conventional materials. These unnatural behaviour come from the periodic arrangement of substructures (cells or units), allowing this type of material to be used in engineering applications to control electromagnetic and mechanical waves in several ways. However, more recently, researchers became interested in programmable metamaterials due to the possibility of controlling the constitutive properties of the material without the need of changing physical parts. This research project aims to design and realize a programmable and adaptive nonlinear electroelastic metamaterial that can be used for vibration or acoustics isolation. The constitutive parameters of such material, namely mass, stiffness and nonlinear coefficients, should be changeable through the use of periodically attached controllable or adaptive electrical impedances by using electromagnetic transducers rather than the common piezoelectric materials. The expected outcomes of this research project are new insights regarding analytic, numerical and experimental approaches for realizing nonlinear electromechanical metamaterial that paves the way for applications in mechanical and aerospace engineering problems. This research project is also linked to the ENVIBRO – Periodic Structure Design and Optimization for Enhanced Vibroacoustics Performance thematic project.
Willian Minnemann Kuhnert
Project Title: Design and realization of a programmable nonlinear electroelastic metamaterial
Supervisor: Carlos De Marqui Junior
Fapesp Grant: 2020/15040-1
Doctoral Students
Abstract: Phononic crystals and metamaterials are commonly classified as engineered materials that have special properties that are not found in natural materials. They have received increasing attention from researchers in recent years. In the case of acoustic metamaterials with periodic arrangements, the exhibition of frequency bands where the wave propagation is predominantly non-propagating (band gaps) shows remarkable potential in several applications, such as vibration isolation, acoustic cloaking, acoustic lenses and others. Micro-perforated duct or panel are acoustic filters composed by a thin tube or plate across whose surface are distributed holes of sub-millimetric size, respectively. They provides high acoustic resistance and low mass reactance due to the size of its holes in which they promote the dissipation of the acoustic energy of the incident sound wave. In this work, it is intended to use this devices arranged as a metamaterial, i.e. using periodicity and/or local resonance, in order to produces large frequency band gaps that will improves its capacity to attenuates the sound. Therefore, the present research project aims to study such acoustic metamaterial in order to develop analytical and numerical design tolls with experimental verification. In addition, it is also the aim to optimize this metamaterial in order to maximize its sound attenuation performance.
Adriano Mitsuo Goto
Project Title: Sound attenuation of a periodic array of micro perforated ducts and panels
Supervisor: Jose Maria Campos dos Santos
Fapesp Grant: 2019/16794-2
Abstract: In this research project proposal, different wave-based methods are presented as auxiliary tools in the development of an original numerical model capable of describing the dynamic behavior of nonlinear periodic structures. The increasing number of studies in the field of wave propagation and periodic structures propel the search for additional analysis techniques and solve engineering problems. Periodic structures arise in this context because of their ability to reorganize wave propagation and act as mechanical filters. A brief literature review is able to demonstrate the wide range of applications of these systems. However, there is a large gap regarding the study of nonlinear periodic structures. In this sense, the present project proposes the use of the wave or finite element method and the harmonic equilibrium method as bases to develop numerical models applied to the study of nonlinear periodic structures. Besides, it is proposed to apply the perturbation method and determine the forced response of the proposed system. The results will be analyzed and the method will be optimized. Experimental procedures will be performed in order to validate and indicate the efficiency of the developed method in the design of nonlinear periodic structures applied to real cases. The conclusions will contribute to the study of periodic structures, as well as to wave propagation analysis and design of nonlinear periodic structures applied to solve engineering problems.
Jean Paulo Carneiro Junior
Project Title: Modeling, Design and Experimental Analysis of Nonlinear Periodic Structures
Supervisor: Michael J. Brennan / Paulo J. Paupitz Gonçalves
Fapesp Grant: 2019/19335-9
Abstract: The large majority of investigations dedicated to periodic structures are based on the assumption of perfect periodicity, i.e., that all the unit cells that compose the structures present exactly the same physical and geometrical characteristics. However, owing to variabilities introduced during material processing and manufacturing, in practical cases periodicity is not perfect. In these cases, one has the so-called quasi-periodic structures. It has been demonstrated that the breakage of periodicity can generate the so called localization phenomenon, which is characterized by the confinement of the motion in a rather small region of the structure. In this context, the objectives of this doctorate project are: * development, implementation and validation of a methodology for the modeling of quasi-periodic structures under various types of deterministic and random disturbances (in geometry, material properties and boundary conditions); * investigation of the conditions under which localization phenomena occur in quasi-periodic structures; * investigation of the possibility of exploring the localization phenomenon to enhance the effectiveness of energy harvesting from vibration motion using piezoelectric transducers. * design and manufacturing of an experimental demonstrator of localization phenomena and energy harvesting.
Matheus Basílio Rodrigues
Project Title: Investigation of localization effects in quasi-periodic structures in association with piezoelectric energy harvesting
Supervisor: Domingos A. Rade
Fapesp Grant: 2019/19921-5
Undergrad Students – Scientific Initiation
Rhamy Salim Bachour
Abstract: In this work, we study the dynamic behavior of rotors built by additive manufacturing (3D printing). First, we design and test them experimentally in a test rig and check their unbalance response. Second, we adjust a mathematical model according to the experimental data. With this model, we design a rotor with geometric periodicity and test it experimentally. The geometric periodicity introduces interesting dynamic characteristics in the system, such as bandgaps in the frequency response, which is quite important to light rotating systems as the ones built by additive manufacturing.
Project Title: Numerical and Experimental Analysis of Rotors with Geometric Periodicity and Additive Manufacturing
Supervisor: Rodrigo Nicoletti
Danilo Braghini
Abstract: Interface modes have been investigated by the student on a first stage of Scientific Initiation. In this initial study, the phononic crystal (PC) from the work of Carneiro et al. (Carneiro et al., 2018) that is based on elastic rods, was used with the intention of understand and extrapolate the geometric phase determination methods developed in scientific literature (Xiao et al., 2014). To this end, the experimental data from the work of Carneiro et al. was used. Nevertheless, our attempts to obtain the geometric phases have not obtain success yet. Therefore, the suggestion is to focus the efforts upon that purpose. To perform such investigations, it is paramount to study the physical models and the mathematical methods that are more often used on the analysis of such periodic systems. The student has already been considering the topic and thus he could expose a brief historical review, tracing back to the pythagorean studies of sound until more recently elaborated methods that rely on spectral analysis. Moreover, this text summarizes the lumped elements model and the models obtained from the spectral element method or SEM. Aiming validation of the models, it is made a comparison with the results from the classic modal analysis. In the light od two fundamental tools – dispersion relation diagrams and the concept of geometric phase (GP) – also previously studied by the student, as shown in the next section, it is proposed to acquire new measures with the model from Carneiro e al. experiment and to calculate the GPs of this system. Additionally, it will be designed a new system of PCs and it will be experimentally described, have in mind to improve the correlation between experimental and simulated data and develop deep understanding on the interpretation of the geometric phases for prediction of topological modes in elastic crystals.
Project Title: Investigating Topological Modes in Acoustic and Elastic One-dimensional Waveguides
Supervisor: Jose Roberto de França Arruda
Fapesp Grant: 2019/20235-9
Renan Trevizan de Melo
Abstract: This project is intended to modify the transmissibility characteristics of a metamaterial leveraging non-uniform tuning of locally resonating systems (resonators) associated with the main structure. Typically, the natural frequencies of the resonators are evenly tuned at a certain target frequency. As a result, the transmissibility (structural response to excitation ratio) is drastically reduced for a certain range of excitation frequencies starting at the target frequency. The width of such a frequency range (bandgap), however, strongly depends on the added mass (the more the added mass, the wider the bandgap). Therefore, the motivation for this project is to achieve configurations that lead to wider bandgaps while reducing the system mass. The results of this project are expected to support future research in which the resonators non-uniformity could be promoted by smart materials (such as piezoceramics and/or shape-memory alloys). In such a case, real time tuning of the resonators could take place as the excitation characteristics change, yielding an adaptive system.
Project Title: Elastic metastructures leveraging non-uniform locally resonating systems for transmissibility enhancement
Supervisor: Vagner Candido de Sousa
Fapesp Grant: 2019/25680-0
Abstract: This project aims at the study of mechanical structures with integrated vibration absorption, known as meta-structures. Based on the concept of metamaterials, these structures exhibit a certain periodicity, because a building unit is repeated throughout its formation. The attenuation of undesired waves in these structures is performed by dynamic vibration absorbers distributed along the structural matrix. These passive absorption devices may have linear or non-linear characteristics. In the literature, numerous studies prove the effectiveness of the use of these linear oscillators in the control of vibration in mechanical systems. In recent years, resonators with nonlinear features have also gained attention. However, the effects of nonlinearities on design components are still little explored, due to the complexity of the analysis of this phenomenon. In this context, the objective of this project is to understand the dynamic interaction of non-linear absorbers in meta-structures. Influences of nonlinear stiffness on the decay of vibration-free energy in the primary structure will be evaluated.
Felipe Alves Anézio
Project Title: A study of nonlinear stiffness influence on periodic structures
Supervisor: Paulo J. Paupitz Gonçalves
Fapesp Grant: 2019/07042-7
Matheus Cunha Prado
Abstract: Metamaterials and metastructures have several applications such as noise and vibration attenuation, acoustic absorption and isolation, shock and vibration reduction, control and guiding of wave propagation, among others. They are inspired in phononic crystals that exhibit bandgaps, that are frequency ranges in which elastic and acoustic waves do not propagate. However, bandgaps in metamaterials depend on local resonator properties, that act as vibration absorbers, and not on the dimension of periodic cells. This concept has motivated the search for designed structures with local resonators based on metamaterials, so-called metastructures, that could exhibit bandgaps in the low frequency range for relatively small structures. Several research groups have explored the viability of vibration absorbers in light flexible structures, including the use of distributed small mechanical vibration absorbers. There is a growing interest on the use of internal resonances to improve the control of structural vibrations, while there is also need for advancement in the existing techniques and solutions. The main objective of this research proposal is to study the optimization of internal resonators in metastructures to improve the control of structural vibrations.
Project Title: Optimization of internal resonators for the design of quasi-periodic metastructures
Supervisor: Marcelo Areias Trindade
Fapesp Grant: 2021/01937-2