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Symmetry
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Dynamic Systems and Mechanics
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Dynamic Systems and Mechanics

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Engineering and Materials".

Deadline for manuscript submissions: closed (15 December 2022) | Viewed by 9992

Special Issue Editors

Prof. Dr. Polidor Bratu

E-Mail Website
Guest Editor
1. Institute of Solid Mechanics, Romanian Academy, Bucharest, Romania 2. Research Institute for Construction Equipment and Technology—ICECON SA, 021652 Bucharest, Romania
Interests: Nonlinear dynamics, nonlinear vibrations, stability
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Gilbert-Rainer Gillich

E-Mail Website
Guest Editor
Department of Engineering Science, Babeș-Bolyai University Cluj-Napoca, 320085 Resita, Romania
Interests: vibration; damage detection; signal analysis; structural engineering
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Doru-Nicolae Stanescu

E-Mail Website
Guest Editor
National University of Science and Technology POLITEHNICA Bucharest, Pitești University Center
Interests: mechanics of systems, non-linear vibrations, dynamical systems, stability, chaos, numerical analysis.
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Mechanical systems are material structures in the form of solid bodies with elastic, viscous, or plastic connections, made so as to satisfy the functional, structural, strength, and stability requirements specific to a particular engineering project. Essentially, the class of mechanical systems comprises the following categories:       

  • structures of rigid bodies or deformable bodies with connections;
  • dynamic equipment and machines whose functional performance can be expressed by vibration or technological force parameters;
  • support platforms for the viscoelastic support of optoelectronic equipment, lasers, and Gamma ray generators;
  • systems and devices for protection against noise, vibration, and seismic movements; structures, buildings, bridges, and viaducts with protection against seismic movements;

  • biosystems for analyzing the behavior of the human body in variable motion in time and space.

The mechanics of mechanical systems, equipment, machines, and human–machine–environment interaction require us to develop innovative methods for the analysis and synthesis of dynamic behavior in various structural configurations, states, and evolutions under the influence of external actions of a kinematic or dynamic kind.

Systemic symmetry/asymmetry is a basic concept in structural assessments of mass distribution, stiffness, damping, and variable forces over time, and allows for significant influences to be highlighted in the final parametric results of engineering interest. The description of physical/geometric and linear/nonlinear behavior must be correlated with systemic symmetry properties.

Topics of interest include, but are not limited to:

  1. dynamics of rigid/deformable bodies with elastic/viscous/linear/nonlinear connections excited by deterministic/random external actions;
  1. dynamics of body systems with geometric/mass/elastic/damping/harmonic/poly-harmonic /random deterministic excitation natural source (earthquakes) or anthropogenic (industrial, road, aerial CF, etc.) symmetry/asymmetry;
  1. dynamics of machines and equipment generating technological vibrations for industrial works, roads, railways, bridges, and construction. Effects of the physical, geometric, and inertial symmetry/asymmetry conditions of the external action;
  1. rheological models of viscous–elastoplastic connections of special structures with symmetries/asymmetries for buildings, bridges, viaducts, nuclear objectives, platforms, and construction projects with dynamic insulation;
  1. mechanical modeling of systems for the protection of vital equipment in hospitals while maintaining a state of physical and functional integrity with respect to seismic actions or anthropogenic shocks;
  1. behaviour of materials, structures, and functional equipment subject to the action of external vibrations;
  1. modal analysis of body systems with elastic connections and physical, geometric, or mass symmetry/asymmetry;
  1. dynamic processes that modify the rigidity, damping, degradation, fatigue, or defect characteristics of dynamic systems in a long-term functioning regime;
  1. dynamics of buildings, bridges, viaducts, nuclear objective platforms, and base isolation systems;
  1. biomechanical and psycho-sensorial models of the effects of vibrations on people in living, working, and resting spaces;
  1. effects of vibrations on buildings with degradation effects, with resistance and stability diminution, or that have collapsed. Level of severity of anthropic vibrations caused by external/internal sources or seismic movements. Monitoring the level of dynamic actions on construction projects of special or major importance.

Prof. Dr. Polidor Bratu
Prof. Dr. Gilbert-Rainer Gillich
Prof. Dr. Doru-Nicolae Stanescu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • dynamic systems
  • dynamic machines and equipment
  • viscous–elastic connections
  • effects of vibrations on buildings
  • linear/nonlinear models
  • symmetries/asymmetries with significant effects on dynamic behavior
  • defects and structural degradation due to dynamic actions
  • operating mode optimization for dynamic equipment with technological vibrations
  • models for calculating base isolation
  • base insolation systems

Published Papers (7 papers)

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Research

13 pages, 7642 KiB  
Article
New Tribological Aspects in the Micro-Areas of the Symmetric Rolling-Sliding Contact
by Antoni John, Henryk Bakowski, Ioan Száva and Sorin Vlase
Symmetry 2022, 14(8), 1523; https://0-doi-org.brum.beds.ac.uk/10.3390/sym14081523 - 26 Jul 2022
Cited by 1 | Viewed by 1139
Abstract
The study of wear that occurs during operation in the wheel–rail assembly is a difficult process to analyze. The phenomena that accompany the wear process are extremely complex and involve many factors, which vary greatly over different periods of time and at different [...] Read more.
The study of wear that occurs during operation in the wheel–rail assembly is a difficult process to analyze. The phenomena that accompany the wear process are extremely complex and involve many factors, which vary greatly over different periods of time and at different times of wheel–rail contact. Estimating the behavior of the system and its wear in operation is difficult to obtain. However, for common engineering applications, for which the determining factors, such as road profile, load, skid, speed and weather conditions, are known, useful results can be obtained by laboratory tests or by numerical simulation. The article aims to model the complex phenomena that take place in the rail wheel system, taking into account the impact that most essential operational factors have. For this, the Finite Element Method (FEM) is used, thus, trying to explain the wear mechanisms of the wheel–rail system. The obtained results are verified in the laboratory. The main observation in the paper refers to the fact that in the areas of maximum stress and deformation, cracks appear at the micro scale. FEM proved to be a method that can predict the appearance of these microcracks, the experimental results validating the numerical experiments. The research offers results that can prove to be of great importance in practice, for the analysis and improvement of railway safety. Full article
(This article belongs to the Special Issue Dynamic Systems and Mechanics)
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20 pages, 3625 KiB  
Article
Dynamic Response of Vibratory Piling Machines for Ground Foundations
by Adrian Mihai Goanță, Polidor Bratu and Nicușor Drăgan
Symmetry 2022, 14(6), 1238; https://0-doi-org.brum.beds.ac.uk/10.3390/sym14061238 - 14 Jun 2022
Cited by 4 | Viewed by 1428
Abstract
Vibrating technological equipment for the introduction of piles and columns into the ground of construction foundations (named vibratory piling machines) is crucial in the process of building stable and resilient foundations for civil engineering, hydrotechnical construction, special construction (e.g., military constructions), bridges, roads [...] Read more.
Vibrating technological equipment for the introduction of piles and columns into the ground of construction foundations (named vibratory piling machines) is crucial in the process of building stable and resilient foundations for civil engineering, hydrotechnical construction, special construction (e.g., military constructions), bridges, roads and industrial platforms. During the works carried out by the construction companies in various geographical areas of Romania, particularities of the dynamic technological regimes influenced by the nature of the land were identified at the deep introduction of the construction elements in the form of piles or circular (tubular) columns. The results of applied research, rheological modeling and optimization of vibrating equipment, highlight the need for an analytical approach that takes into account the parametric variations of the elastic and damping characteristics of some categories of soils on the depth of piles or foundation columns. In this context, the paper presents the calculation model with the dynamic response for the vibrating equipment of insertion with disturbing forces of 200–1250 kN for piles or columns with lengths of 10–30 m. The novelty of the research study consists in the linear rheological model, which was adopted in the form of a Maxwell–Voigt–Kelvin schematic of the type (E-V)–(E|V), with a discrete variation in four values for stiffness and damping of the soil, as the piles or columns vibrate and advance in the ground foundation. Practical experience of the authors in the field of using vibrogenerators for the introduction of piles in various types of ground foundations led to the adoption of the rheological model with variable damping coefficients depending on the depth of penetration into the soil. The curves of the dissipated power confirm the experimental data obtained in situ, in accordance with the rheological indoor tests of the different types of soil foundations. Full article
(This article belongs to the Special Issue Dynamic Systems and Mechanics)
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56 pages, 10770 KiB  
Article
On the Vibrations of a Rigid Solid Hung by Kinematic Chains
by Alin-Florentin Stan, Nicolae Pandrea, Nicolae-Doru Stănescu, Ligia Munteanu and Veturia Chiroiu
Symmetry 2022, 14(4), 770; https://0-doi-org.brum.beds.ac.uk/10.3390/sym14040770 - 07 Apr 2022
Cited by 1 | Viewed by 1230
Abstract
In this paper we consider two situations. In the first, all kinematic chains are elastic, while the second situation is characterized by one rigid kinematic chain, with the rest of them being elastic. In addition, the kinematic joints are considered to be rigid. [...] Read more.
In this paper we consider two situations. In the first, all kinematic chains are elastic, while the second situation is characterized by one rigid kinematic chain, with the rest of them being elastic. In addition, the kinematic joints are considered to be rigid. The calculations are performed using the screw coordinates. For the free vibrations of the rigid solid we determined the rigidity matrix and the eigenpulsations in both cases. It was proved that the results in the second case cannot be considered as limits for the results of the first situation, putting infinite values for the elements of the rigidity matrix of one kinematic chain. We also developed the theory for the forced vibrations of the system. A numerical application is considered and a great variety of cases are developed and discussed. The results obtained for the forced vibrations are presented and discussed. The paper combines elastic and rigid kinematic chains, as well as general configurations of the kinematic chains. The method presented here may be used for any number of kinematic chains, no matter if the structure is symmetrical or asymmetrical. Full article
(This article belongs to the Special Issue Dynamic Systems and Mechanics)
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16 pages, 3427 KiB  
Article
Dynamic Performances of Technological Vibrating Machines
by Polidor Bratu, Nicușor Drăgan and Cornelia Dobrescu
Symmetry 2022, 14(3), 539; https://0-doi-org.brum.beds.ac.uk/10.3390/sym14030539 - 07 Mar 2022
Cited by 4 | Viewed by 1744
Abstract
Based on the research carried out within the Research Institute for Construction Equipment and Technology—ICECON S.A. Bucharest, consisting of the design and development of vibrating-action machines and of the technical analysis of optimization of the technological processes with vibrating equipment for highway construction [...] Read more.
Based on the research carried out within the Research Institute for Construction Equipment and Technology—ICECON S.A. Bucharest, consisting of the design and development of vibrating-action machines and of the technical analysis of optimization of the technological processes with vibrating equipment for highway construction works in Romania. Moreover, the physical and mathematical modeling of this mechanical system used the data obtained in the activity of the certification of the technical level of capability of the processing equipment in industry and construction, taking into account the provisions of procedures and regulations legally enforced by normative documents. These are based on a parametric analysis of the dynamics of the technological processing vibratory equipment and machines. Thus, both the evaluation method and the parametric optimization procedure were established. In this context, this paper presents a numerical analytical approach with discrete and continuous parametric variations, from where favorable areas of operation can be established. In this way, the optimization criteria in stabilized harmonic vibration regimes are approached based on the assessment of the vibration amplitude, of the force transmitted to the processed material and of the energy dissipated in the system. The presented dynamic model as well as the specific parameters were used in the design and/or numerical and experimental assessment for vibrating rammers with the amplitude of the perturbing force from 2 kN up to 100 kN, vibrating compactors with the amplitude of the perturbing force from 100 kN up to 200 kN and vibrating sieves for mineral aggregates with surface sieves of 6, 12 and 18 sqm. The symmetry/asymmetry properties are specific to the dynamic response in steady-state technological regime. Thus, the amplitude of vibrations in resonance presents asymmetry through a functional level necessary for the technological regime. The maximum force transmitted in the technological process is asymmetric in relation to the variation of the excitation pulsation; also, the dissipated energy has asymmetries in the postresonance. Hysteresis loops are symmetrical to the main axis. The originality of the research results comes from the establishment of dynamic parameters for the amplitude of technological vibration, the force transmitted to the working part, the energy dissipated on the cycle, hysteresis loops in a steady-state regime with digital display to identify the dynamic regime and the damping in the system. The calculation relations are specific to machines with a vibrating action and, on their basis, the vibrating equipment from Romania were designed, manufactured and tested, as mentioned in this paper. Full article
(This article belongs to the Special Issue Dynamic Systems and Mechanics)
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13 pages, 3657 KiB  
Article
Hysteresis Response Loops in Stationary Vibrator Regimes for Elastomeric Insulators
by Polidor Bratu, Cornelia Dobrescu and Nicu Drăgan
Symmetry 2022, 14(2), 246; https://0-doi-org.brum.beds.ac.uk/10.3390/sym14020246 - 27 Jan 2022
Viewed by 1825
Abstract
In order to raise the hysteresis loops in stationary dynamic regimes in the case of elastomeric insulators, specialized dynamic stands are used that may obtain both the necessary harmonic excitation by force as well as the modification of the angular arrangement discreetly variable [...] Read more.
In order to raise the hysteresis loops in stationary dynamic regimes in the case of elastomeric insulators, specialized dynamic stands are used that may obtain both the necessary harmonic excitation by force as well as the modification of the angular arrangement discreetly variable from zero to 90 degrees. In this context, for the evaluation of the elastomeric insulators, a dynamic stand with an inertial vibrator was used, the frequency of which can be changed by continuous adjustment within the range of values from 2 Hz to 60 Hz. Forces and displacements can be measured with the appropriate sensors, and based on the recording of signals, the characteristics of rigidity, damping and the raise of hysteresis loops could be determined for three significant dynamic regimes: ante-resonance and post-resonance. Research on the dynamic stand, patented in Romania, has highlighted the fact that the parametric evaluation can be performed based on the lifting of the hysteretic loops in stationary harmonic regimes. Additionally, there are two situations specifically mentioned, one in which the significant inertial effect for the F-x loops leads to their positioning in quadrants II and IV, and the case of Q-x loops, where the inertial effect does not exist, and their positioning is only in quadrants I and III. From the analysis of the two cases, the most advantageous evaluation method for the test can be chosen. This article provides the calculation relationships established for the dynamic model with linear viscoelastic behaviour. The requirements of Voight–Kelvin modeling with a single degree of freedom is fully justified and ensured by the conditions of geometric and mass symmetry in the construction of the stand. The verification of the numerical results with the experimental ones was performed with the hysteresis loops corresponding to the previously defined three significant dynamic regimes, as well as according to the three positions of the elastomeric insulators for compression, compression-shear and shear. Full article
(This article belongs to the Special Issue Dynamic Systems and Mechanics)
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43 pages, 5100 KiB  
Article
Simultaneous Collision of the Rigid Body at Two Points
by Ionuț-Bogdan Dragna, Nicolae Pandrea and Nicolae-Doru Stănescu
Symmetry 2021, 13(10), 1924; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13101924 - 13 Oct 2021
Cited by 2 | Viewed by 1204
Abstract
We present a new approach based on the notion of inertance for the simultaneous collisions without friction of a rigid solid. The calculations are performed using the screw (plückerian) coordinates, while the results are obtained in matrix form, and they may be easily [...] Read more.
We present a new approach based on the notion of inertance for the simultaneous collisions without friction of a rigid solid. The calculations are performed using the screw (plückerian) coordinates, while the results are obtained in matrix form, and they may be easily implemented for different practical situations. One calculates the velocities after collision, the energy of lost velocities, and the loss of the kinetic energy. The general algorithm of calculation is described in the paper. The main assumption is that the normal velocities at the contact points vanish simultaneously. The coefficients of restitution at the contact points may be equal or not. Some completely solved applications are also presented, and the numerical results are discussed. The numerical values depend on which coefficient of restitution is used. Full article
(This article belongs to the Special Issue Dynamic Systems and Mechanics)
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13 pages, 3110 KiB  
Article
Optimization of Generatively Encoded Multi-Material Lattice Structures for Desired Deformation Behavior
by Petar Ćurković
Symmetry 2021, 13(2), 293; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13020293 - 09 Feb 2021
Cited by 5 | Viewed by 2422
Abstract
Natural systems achieve favorable mechanical properties through coupling significantly different elastic moduli within a single tissue. However, when it comes to man-made materials and structures, there are a lack of methods which enable production of artifacts inspired by these phenomena. In this study, [...] Read more.
Natural systems achieve favorable mechanical properties through coupling significantly different elastic moduli within a single tissue. However, when it comes to man-made materials and structures, there are a lack of methods which enable production of artifacts inspired by these phenomena. In this study, a method for design automation based on alternate deposition of soft and stiff struts within a multi-material 3D lattice structure with desired deformation behavior is proposed. These structures, once external forces are applied, conform to the geometry given in advance. For that purpose, a population-based algorithm was proposed and integrated with a multi-material physics simulator. To reduce the amount of data processed during optimization, a generative encoding method based on discrete cosine transform (DCT) was proposed. This enabled a compressed topological description and promoted symmetry in material distribution. The simulation results showed different three-dimensional lattice structures designed with proposed algorithm to meet a set of desired deformation behaviors. The relation between residual deformation error, targeted deformation geometry, and material distribution is discussed. Full article
(This article belongs to the Special Issue Dynamic Systems and Mechanics)
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