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This paper deals with the area of structural damage monitoring of steel strands wire ropes embedded into various equipment and mechanical systems. Of the currently available techniques and methods for wire ropes health monitoring, the authors focused on the group of techniques based on operational dynamics investigation of such systems. Beyond the capability and efficiency of both occasionally and continuously monitoring application, the dynamics-based methods are able to provide additional information regarding the structural integrity and functional operability of the entire ensemble embedding the wire ropes. This paper presents the results gained by the authors using a laboratory setup that can simulate the operational condition usually used for regular applications of wire ropes. The investigations were conducted on three directions of acquired signals post-processing. Firstly, the classical fast Fourier transform was used to evaluate the potential changes within the spectral distribution of transitory response. The other two directions involved high-order spectral analyses in terms of bi-spectrum and Wigner–Ville distribution and multi-scale analysis based methods such as complex wavelet cross-correlation and complex wavelet coherency. The results indicate that each direction of analysis can provide suitable information regarding potential wire rope damage, but the ensemble of post-processing methods offers supplementary precision.
Carmen Debeleac; Silviu Nastac; Gina Diana Musca (Anghelache). Experimental Investigations Regarding the Structural Damage Monitoring of Strands Wire Rope within Mechanical Systems. Materials 2020, 13, 3439 .
AMA StyleCarmen Debeleac, Silviu Nastac, Gina Diana Musca (Anghelache). Experimental Investigations Regarding the Structural Damage Monitoring of Strands Wire Rope within Mechanical Systems. Materials. 2020; 13 (15):3439.
Chicago/Turabian StyleCarmen Debeleac; Silviu Nastac; Gina Diana Musca (Anghelache). 2020. "Experimental Investigations Regarding the Structural Damage Monitoring of Strands Wire Rope within Mechanical Systems." Materials 13, no. 15: 3439.
The Lagrange’s equation remains the most used method by researchers to determine the finite element motion equations in the case of elasto-dynamic analysis of a multibody system (MBS). However, applying this method requires the calculation of the kinetic energy of an element and then a series of differentiations that involve a great computational effort. The last decade has shown an increased interest of researchers in the study of multibody systems (MBS) using alternative analytical methods, aiming to simplify the description of the model and the solution of the systems of obtained equations. The method of Kane’s equations is one possibility to do this and, in the paper, we applied this method in the study of a MBS applying finite element analysis (FEA). The number of operations involved is lower than in the case of Lagrange’s equations and Kane’s equations are little used previously in conjunction with the finite element method (FEM). Results are obtained regardless of the type of finite element used. The shape functions will determine the final form of the matrix coefficients in the equations. The results are applied in the case of a planar mechanism with two degrees of freedom.
Sorin Vlase; Iuliu Negrean; Marin Marin; Silviu Năstac. Kane’s Method-Based Simulation and Modeling Robots with Elastic Elements, Using Finite Element Method. Mathematics 2020, 8, 805 .
AMA StyleSorin Vlase, Iuliu Negrean, Marin Marin, Silviu Năstac. Kane’s Method-Based Simulation and Modeling Robots with Elastic Elements, Using Finite Element Method. Mathematics. 2020; 8 (5):805.
Chicago/Turabian StyleSorin Vlase; Iuliu Negrean; Marin Marin; Silviu Năstac. 2020. "Kane’s Method-Based Simulation and Modeling Robots with Elastic Elements, Using Finite Element Method." Mathematics 8, no. 5: 805.
Recent studies have highlighted an innovative way to produce highly porous materials based on cellulose fibers. These studies have focused on the foam-forming process, where the cellulose fibers and other components are mixed with foam. In the authors’ previous research, the foam-formed cellulose materials (FCM) were obtained by mixing a surfactant with cellulose fibers, taken from virgin pulp and recovered papers. In the present paper, the authors performed additional experimental and computational analyses in order to evaluate the sound insulation capabilities of these FCM beyond the initial impedance of tube investigations. The poroacoustics computational methodology parameters—i.e., airflow resistivity, porosity, tortuosity, viscous, and thermal characteristic lengths—were herein evaluated. This analysis was performed using both a theoretical/empirical approach from the specialized literature and an experimental investigation developed by the authors. The computational investigations were conducted in two stages: First, we evaluated the approximation of the experimentally gained normal incidence parameters, in terms of absorption and reflection, respectively, relative to the estimated ones. The second stage of analysis consists of a parametrical estimation of sound insulation characteristics concerning the incidence angle of sound hitting the porous layer. The results presented in this paper are in agreement with the computational experimental results, providing extended soundproof characteristics to the incidence angle of the acoustic field. Further, this study supplies additional information useful for future analyses regarding the influences of random geometry air inclusions into the FCM layer.
Carmen Debeleac; Petronela Nechita; Silviu Nastac. Computational Investigations on Soundproof Applications of Foam-Formed Cellulose Materials. Polymers 2019, 11, 1223 .
AMA StyleCarmen Debeleac, Petronela Nechita, Silviu Nastac. Computational Investigations on Soundproof Applications of Foam-Formed Cellulose Materials. Polymers. 2019; 11 (7):1223.
Chicago/Turabian StyleCarmen Debeleac; Petronela Nechita; Silviu Nastac. 2019. "Computational Investigations on Soundproof Applications of Foam-Formed Cellulose Materials." Polymers 11, no. 7: 1223.
This study deals with computational analysis of vibration isolators' behavior, using the fractional-order differential equations (FDE). Numerical investigations regarding the influences of α-fractional derivatives have been mainly focused on the dissipative component within the differential constitutive equation of rheological model. Two classical models were considered, Voigt-Kelvin and Van der Pol, in order to develop analyses both on linear and nonlinear formulations. The aim of this research is to evaluate the operational capability, provided by the α-fractional derivatives within the viscous component of certain rheological model, to enable an accurate response regarding the realistic behavior of elastomeric-based vibration isolators. The hysteretic response followed, which has to be able to assure the symmetry of dynamic evolution under external loads, and at the same time, properly providing dissipative and conservative characteristics in respect of the results of experimental investigations. Computational analysis was performed for different values of α-fractional order, also taking into account the integer value, in order to facilitate the comparison between the responses. The results have shown the serviceable capability of the α-fractional damping component to emulate, both a real dissipative behavior, and a virtual conservative characteristic, into a unitary way, only by tuning the α-order. At the same time, the fractional derivative models are able to preserve the symmetry of hysteretic behavior, comparatively, e.g., with rational-power nonlinear models. Thereby, the proposed models are accurately able to simulate specific behavioral aspects of rubber-like elastomers-based vibration isolators, to the experiments.
Silviu Nastac; Carmen Debeleac; Sorin Vlase. Hysteretically Symmetrical Evolution of Elastomers-Based Vibration Isolators within α-Fractional Nonlinear Computational Dynamics. Symmetry 2019, 11, 924 .
AMA StyleSilviu Nastac, Carmen Debeleac, Sorin Vlase. Hysteretically Symmetrical Evolution of Elastomers-Based Vibration Isolators within α-Fractional Nonlinear Computational Dynamics. Symmetry. 2019; 11 (7):924.
Chicago/Turabian StyleSilviu Nastac; Carmen Debeleac; Sorin Vlase. 2019. "Hysteretically Symmetrical Evolution of Elastomers-Based Vibration Isolators within α-Fractional Nonlinear Computational Dynamics." Symmetry 11, no. 7: 924.
This study deals with estimation of milling shape accuracy and trajectory conformity for small CNC 3D milling machines, based on vibration monitoring during the regular working cycles. The author made a large number of experimental tests, acquiring the acceleration signals, both on the milling tool-holder and on the bed frame. In order to evaluate the appropriate spectral characteristics of different machine parts and their weights on equipment dynamics, it was analyzed both the complete and the partial working cycle (such as forward tool motion, with or without effective milling, with or without tool driving, exclusively the milling cutter transitory/stabilized regime) for different basic milling shapes. The acceleration signals were jointly time-frequency investigated in order to evaluate specific spectral indicators related to the real motion characteristic of milling tool. It was used short time fast Fourier transform (STFFT) and Hough transform (HT) algorithms, along with stochastic evaluation of signal parameters, within time and frequency domains. The results reveal an accurate correlation between the specific transitory dynamics of the machine and the imposed milling shape. Main implications of the results within this analysis involve the noninvasive and facile investigation for milling errors of the CNC machine, conformity of tool head trajectory, identification of potential failure source, or damaged machine part.
Silviu Nastac. On Vibration Joint Time-Frequency Investigations of CNC Milling Machines for Tool Trajectory Task Conformity Estimation. Shock and Vibration 2018, 2018, 1 -9.
AMA StyleSilviu Nastac. On Vibration Joint Time-Frequency Investigations of CNC Milling Machines for Tool Trajectory Task Conformity Estimation. Shock and Vibration. 2018; 2018 ():1-9.
Chicago/Turabian StyleSilviu Nastac. 2018. "On Vibration Joint Time-Frequency Investigations of CNC Milling Machines for Tool Trajectory Task Conformity Estimation." Shock and Vibration 2018, no. : 1-9.
Nowadays, there are several insulation solutions for bridges or viaducts structures that work based on various insulation principles. The basic principles used in the bridge isolation field are represented by vibration insulation and energy dissipation arising from various dynamic loads acting upon the structure, thus that the devices in use are mainly categorized as isolators or energy dissipation devices. An innovative solution for bridge isolation is described in this paper, which uses a composed system able to use both isolation and dissipation characteristics of these two devices types. It has been designed a particular device model, meaning dual vibration insulation device, which is composed of an elastomeric isolation type system, working in tandem with a dissipative device based on rolling friction. This hybrid device has been built and mounted on a bridge structure achieved on a reduced scale. Thus, the isolated structure has been tested at dynamic actions by generating vibrations within the bridge structure using a special exciting device. According with the obtained results higher acceleration values are recorded at the bridge pier support level, while they are more attenuated at the superstructure level, due to interposing of the dual vibration insulation device between the bridge pier and the superstructure. This type of composed isolation device provides additional degrees-of-freedom within the entire ensemble, thus that the bridge support pier can move along with the foundation soil, which induces the dynamic loads, while the superstructure is able to maintain a steady-state dynamic regime without being affected, in a considerable way, by ground movements. In this paper, are presented the results recorded on the experimental model at the bridge support pier and superstructure level regarding the time and the frequency evolutions of the acceleration signals.
Fanel Scheaua; Silviu Năstac. On Dynamics of a Dual Vibration Insulation Device Based on Elastomeric Kernel and Rolling Friction Dissipation. Springer Proceedings in Physics 2017, 397 -403.
AMA StyleFanel Scheaua, Silviu Năstac. On Dynamics of a Dual Vibration Insulation Device Based on Elastomeric Kernel and Rolling Friction Dissipation. Springer Proceedings in Physics. 2017; ():397-403.
Chicago/Turabian StyleFanel Scheaua; Silviu Năstac. 2017. "On Dynamics of a Dual Vibration Insulation Device Based on Elastomeric Kernel and Rolling Friction Dissipation." Springer Proceedings in Physics , no. : 397-403.
This study deals with operational modal identification techniques area, presenting a group of experimental and computational approaches about refining of modal characteristics for structural parts during their dynamic exploitation regime. Hereby, it can be included both into the modal experimental/operational analysis domain—with application in dynamic state evaluation in order to provide essential information to vibration control measures, and into the structural health monitoring area—providing a feasible tool for compiling the referenced state and estimating the failure imminence. The analyses were developed based on the laboratory setup, taking into account a simple structural element with constant mechanical and geometrical characteristics. The theoretical approaches contain both analytical evaluations, and computational simulations with the help of the finite element method. The results comparison between the classical modal identification techniques and the proposed method reveals an improved capability of the last for modal characterization of a singular structural element within its dynamic evolution, also taking into account that the number of experimental measurements was constantly maintained. Future developments will take into consideration the applicability of these assessments for structural ensembles or variable characteristic elements.
Silviu Nastac; Carmen Debeleac. Assessments on Operational Modal Identification Refining of a Structural Element. Springer Proceedings in Physics 2017, 323 -329.
AMA StyleSilviu Nastac, Carmen Debeleac. Assessments on Operational Modal Identification Refining of a Structural Element. Springer Proceedings in Physics. 2017; ():323-329.
Chicago/Turabian StyleSilviu Nastac; Carmen Debeleac. 2017. "Assessments on Operational Modal Identification Refining of a Structural Element." Springer Proceedings in Physics , no. : 323-329.
This paper deals with computational nonlinear dynamics of mechanical systems containing some flexural parts within the actuating scheme, and, especially, the situations of the cable-based driving systems were treated. It was supposed both functional nonlinearities and the real characteristic of the power supply, in order to obtain a realistically computer simulation model being able to provide very feasible results regarding the system dynamics. It was taken into account the transitory and stable regimes during a regular exploitation cycle. The authors present a particular case of a lift system, supposed to be representatively for the objective of this study. The simulations were made based on the values of the essential parameters acquired from the experimental tests and/or the regular practice in the field. The results analysis and the final discussions reveal the correlated dynamic aspects within the mechanical parts, the driving system, and the power supply, whole of these supplying potential sources of particular resonances, within some transitory phases of the working cycle, and which can affect structural and functional dynamics. In addition, it was underlines the influences of computational hypotheses on the both quantitative and qualitative behaviour of the system. Obviously, the most significant consequence of this theoretical and computational research consist by developing an unitary and feasible model, useful to dignify the nonlinear dynamic effects into the systems with cable-based driving scheme, and hereby to help an optimization of the exploitation regime including a dynamics control measures.
G D Anghelache; S Nastac. Computational analysis of nonlinearities within dynamics of cable-based driving systems. IOP Conference Series: Materials Science and Engineering 2017, 227, 012007 .
AMA StyleG D Anghelache, S Nastac. Computational analysis of nonlinearities within dynamics of cable-based driving systems. IOP Conference Series: Materials Science and Engineering. 2017; 227 (1):012007.
Chicago/Turabian StyleG D Anghelache; S Nastac. 2017. "Computational analysis of nonlinearities within dynamics of cable-based driving systems." IOP Conference Series: Materials Science and Engineering 227, no. 1: 012007.
Use of foam-formed cellulose composite materials is a viable alternative that provides potential savings in terms of raw materials, energy and water compared with conventional methods for obtaining the fibrous composites. This new innovative manufacturing method leads to obtaining porous materials with low density and low environmental impact, which could replace the petroleum-based products in different industrial application fields like sound control. In this paper is presented a methodology for producing low-density cellulose composite materials in foam media. In this methodology a surfactant is mixed with cellulose fibres (from virgin pulp and recovered papers) at high shear velocity (2000 r/min) to entrain air, dewatered on Buchner funnel under low vacuum and air dried in non-restrained conditions. The obtained composite materials have been tested by sound insulation parameters (sound transmission loss and absorption coefficients) using two experimental impedance tubes with four-microphone configuration and anechoic termination. Three samples of foam-formed cellulose composites and one water-formed composite sample were obtained. Their sound insulation performances were compared with two different commercially available petroleum-based materials currently used in sound insulation applications (i.e. expanded/extruded polystyrene). The experimental results show comparable performances between foam-formed cellulose composites and polystyrene-based samples, but in terms of the environmental impact, these materials can be an appropriate green alternative which can cut the costs of recycling process.
P Nechita; S Năstac. Foam-formed cellulose composite materials with potential applications in sound insulation. Journal of Composite Materials 2017, 52, 747 -754.
AMA StyleP Nechita, S Năstac. Foam-formed cellulose composite materials with potential applications in sound insulation. Journal of Composite Materials. 2017; 52 (6):747-754.
Chicago/Turabian StyleP Nechita; S Năstac. 2017. "Foam-formed cellulose composite materials with potential applications in sound insulation." Journal of Composite Materials 52, no. 6: 747-754.
Laurentiu Curduman; Silviu Nastac; Carmen Debeleac; Mircea Modiga. Computational Dynamics of the Rotational Heavy Loads Mastered by Hydrostatical Driving Systems. Procedia Engineering 2017, 181, 509 -517.
AMA StyleLaurentiu Curduman, Silviu Nastac, Carmen Debeleac, Mircea Modiga. Computational Dynamics of the Rotational Heavy Loads Mastered by Hydrostatical Driving Systems. Procedia Engineering. 2017; 181 ():509-517.
Chicago/Turabian StyleLaurentiu Curduman; Silviu Nastac; Carmen Debeleac; Mircea Modiga. 2017. "Computational Dynamics of the Rotational Heavy Loads Mastered by Hydrostatical Driving Systems." Procedia Engineering 181, no. : 509-517.
Laurentiu Curduman; Carmen Debeleac; Silviu Nastac. On Path Oscillations Analysis of Mechanical Multi-body and Hydrostatical Driving Units Coupled System. Procedia Engineering 2017, 181, 518 -525.
AMA StyleLaurentiu Curduman, Carmen Debeleac, Silviu Nastac. On Path Oscillations Analysis of Mechanical Multi-body and Hydrostatical Driving Units Coupled System. Procedia Engineering. 2017; 181 ():518-525.
Chicago/Turabian StyleLaurentiu Curduman; Carmen Debeleac; Silviu Nastac. 2017. "On Path Oscillations Analysis of Mechanical Multi-body and Hydrostatical Driving Units Coupled System." Procedia Engineering 181, no. : 518-525.
Computational dynamics of technological equipments dealing with intensive, shock-like and various working regimes frames the area of this research paper. A widely used type of demolition-cutting equipment supplied by hydrostatical driving system was adopted, and ordinary scenarios of equipment exploitation have been proposed in order to dignify the very short but strong transitory states deeply depending on the material characteristics and the regime parameters. Elastic, dissipative and plastic components have been considered to compose the global characteristic of the processed material interacting with cutting tool. The authors propose a simplified rheological model intended for modeling and simulation of demolished structural elements based on composite materials, like reinforced concrete. This model is very useful for simulation the variable dynamics of the interaction between the demolition-cutting equipments and the composite elements in order to evaluate the parameters evolution within the process, and obviously, to optimize driving system for minimize transitory effects and vibratory evolutions. The advantage of this computational approach results from the reduced resources involved by simulation tasks, taking into account the global evaluation of the resistant forces usually required for this kind of behavioral analysis.
Silviu Năstac; Carmen Debeleac; Cristian Simionescu. Transitory Dynamics Evaluation inside Driving System of Demolition-Cutting Technological Equipment due to Variable Tool-Material Interactions. Applied Mechanics and Materials 2015, 811, 50 -56.
AMA StyleSilviu Năstac, Carmen Debeleac, Cristian Simionescu. Transitory Dynamics Evaluation inside Driving System of Demolition-Cutting Technological Equipment due to Variable Tool-Material Interactions. Applied Mechanics and Materials. 2015; 811 ():50-56.
Chicago/Turabian StyleSilviu Năstac; Carmen Debeleac; Cristian Simionescu. 2015. "Transitory Dynamics Evaluation inside Driving System of Demolition-Cutting Technological Equipment due to Variable Tool-Material Interactions." Applied Mechanics and Materials 811, no. : 50-56.
This paper deals with structural damage identification at vibration isolators with elastomeric-based composite, through continuous or periodical evaluation of behavioral changes of the dynamic characteristics. It has supposed only structural damages of passive isolators, appearing inside the elastomeric core. Theoretical approaches has been provided, computer simulation scenarios regarding some potential critical cases has been developed, and experimental tests has been performed, in order to evaluate main correlation between the levels of structural integrity and the operational performance respectively. Partial results indicate an acceptable sensitivity of this dynamic method with damage detection, and establish next goal of the research in evaluation of the failure imminence and accurately localizing techniques.
Silviu Nastac; Carmen Debeleac; Adrian Leopa. On Dynamic Characteristic of Damaged Elastomeric Vibration Isolators. Applied Mechanics and Materials 2015, 801, 159 -164.
AMA StyleSilviu Nastac, Carmen Debeleac, Adrian Leopa. On Dynamic Characteristic of Damaged Elastomeric Vibration Isolators. Applied Mechanics and Materials. 2015; 801 ():159-164.
Chicago/Turabian StyleSilviu Nastac; Carmen Debeleac; Adrian Leopa. 2015. "On Dynamic Characteristic of Damaged Elastomeric Vibration Isolators." Applied Mechanics and Materials 801, no. : 159-164.
Carmen Debeleac; Silviu Nastac. Stochastic Approaches of Nonlinear Model-Based Simulations for Vibratory Compaction Process. PAMM 2014, 14, 749 -750.
AMA StyleCarmen Debeleac, Silviu Nastac. Stochastic Approaches of Nonlinear Model-Based Simulations for Vibratory Compaction Process. PAMM. 2014; 14 (1):749-750.
Chicago/Turabian StyleCarmen Debeleac; Silviu Nastac. 2014. "Stochastic Approaches of Nonlinear Model-Based Simulations for Vibratory Compaction Process." PAMM 14, no. 1: 749-750.
This study deals with nonlinear internal dissipation inside the vibration isolators based on elastomeric composites. Due to the thermal influences on mechanical characteristics occurs during the regular exploitation regime, both conservative and dissipative components have affected and the main parameters continuously change. Beside the nonlinear behaviour of the assembly containing the isolator device, these changes also affects the thermodynamic regime inside the elastomeric material. The isolator shape also affects the internal thermal dissipation state. This complex behaviour implies nonlinear mathematical models, which have to be able to simulate the realistic viscous and elastic characteristics of such composites subjected to dynamic loads. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Silviu Nastac; Carmen Debeleac. On Shape and Material Nonlinearities Influences about the Internal Thermal Dissipation for Elastomer-Based Vibration Isolators. PAMM 2014, 14, 751 -752.
AMA StyleSilviu Nastac, Carmen Debeleac. On Shape and Material Nonlinearities Influences about the Internal Thermal Dissipation for Elastomer-Based Vibration Isolators. PAMM. 2014; 14 (1):751-752.
Chicago/Turabian StyleSilviu Nastac; Carmen Debeleac. 2014. "On Shape and Material Nonlinearities Influences about the Internal Thermal Dissipation for Elastomer-Based Vibration Isolators." PAMM 14, no. 1: 751-752.
This study deals with the problematic of vibratory equipments driving system taking into account both the requirements of functional performances related to the final technological quality, and the dynamic phenomenon appears during the working cycle according to the transmission way from the energy source to the vibration generator. This analysis provides useful assessments for equipment design no matter the technological machine type. Hereby this study tries to dignify the dynamic state deviations induced by the components characteristics of the driven equipment, and to reveal the means for minimizing the parameters variances.
Carmen Debeleac; Cristian Simionescu; Silviu Nastac. Functional Assessments of Dynamics of the Vibratory-Driven Equipments with Belt Transmissions. Applied Mechanics and Materials 2014, 657, 460 -464.
AMA StyleCarmen Debeleac, Cristian Simionescu, Silviu Nastac. Functional Assessments of Dynamics of the Vibratory-Driven Equipments with Belt Transmissions. Applied Mechanics and Materials. 2014; 657 ():460-464.
Chicago/Turabian StyleCarmen Debeleac; Cristian Simionescu; Silviu Nastac. 2014. "Functional Assessments of Dynamics of the Vibratory-Driven Equipments with Belt Transmissions." Applied Mechanics and Materials 657, no. : 460-464.
This work presents a practical solution intended for dynamic diagnosis of the technical systems based on a set of computational methods for processing and analyzing of the acquired signals. This ensemble of methods leads to the joint time-frequency evaluations and assures a multiple way to estimate the potential damages of certain parts of the tested system. Short-Time-Fourier-Transformation, Cepstrum analysis, power spectral density estimate, together with a group of stochastic estimators composes the structured procedure for dynamic diagnosis. The proposed approach of dynamic diagnosis combines the advantages of the time domain analysis, such as the simplicity and the possibility of parameters investigation during their time evolution, with the power of spectral complex evaluations, sustained by the distribution and shifting trend of spectrum. Hereby it has provided a suitable tool for characterization of spectral composition changes in time during the entire experimental tests. This information is able to reveal the dynamic behaviour changes of supervised parts, components or entire system.
Silviu Nastac; Carmen Debeleac; Cristian Simionescu. Dynamic Diagnosis of Elastic Coupling Transmissions of Technological Equipments Based on Joint Time-Frequency Evaluations. Applied Mechanics and Materials 2014, 657, 465 -469.
AMA StyleSilviu Nastac, Carmen Debeleac, Cristian Simionescu. Dynamic Diagnosis of Elastic Coupling Transmissions of Technological Equipments Based on Joint Time-Frequency Evaluations. Applied Mechanics and Materials. 2014; 657 ():465-469.
Chicago/Turabian StyleSilviu Nastac; Carmen Debeleac; Cristian Simionescu. 2014. "Dynamic Diagnosis of Elastic Coupling Transmissions of Technological Equipments Based on Joint Time-Frequency Evaluations." Applied Mechanics and Materials 657, no. : 465-469.
This analysis deals with one of the basic problem category of vibratory systems, means the complete and complex characterization of elastic and viscous isolators behaviour under dynamic loads such as vibrations, seismic waves, shocks, etc. Usually, the dynamic characteristics of vibration isolators made by elastomeric materials are considered to have a constant shape for a certain practical case. It is ignored the thermal phenomenon inside the isolator block during the exploitation cycles and its influences on the proper characteristic parameters. This usual approximation leads to more or less significant differences between simulation and practical evolution of a vibration isolator subjected to the same dynamic load. Continuous changes of rigidity modulus and/or dissipative characteristics due to internal thermal effects imply aleatory evolution of the isolated system, unstable movements and resonance imminence danger. The partial results of this analysis dignify the linkage between thermal effects into the elastomeric isolator and its essential dynamic parameters. Using of these correlations frames the seismic shock and vibration protective devices designing and deployment areas. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Silviu Nastac; Carmen Debeleac. Estimations on Thermo-mechanical Dynamics of Vibration Elastomeric Isolators. PAMM 2012, 12, 603 -604.
AMA StyleSilviu Nastac, Carmen Debeleac. Estimations on Thermo-mechanical Dynamics of Vibration Elastomeric Isolators. PAMM. 2012; 12 (1):603-604.
Chicago/Turabian StyleSilviu Nastac; Carmen Debeleac. 2012. "Estimations on Thermo-mechanical Dynamics of Vibration Elastomeric Isolators." PAMM 12, no. 1: 603-604.
The complete and correct identification and evaluation of proper characteristics of terrain for embankment works is the frame idea of this analysis. The study began from the necessity of vibratory working tools utilization for different construction jobs. Mainly, the simple dynamic calculus is used for estimation of proper parameters values for this kind of works. It supposes a linear characteristic of the material in interaction with vibrating tool and it estimates the domain of working parameters. But instrumental tests reveal that the terrain has a non‐linear characteristic and the dynamic behaviour acquires deviation from theoretical estimations. An identification procedure followed by a correct and complete evaluation of the non‐linear parameters gives the necessary information for a practical case. Available mathematical models require a lot of initial values for characteristic parameters, but changing the case changes the values. A complex model which needs only initial tuning offers a proper solution to simulate, estimate, evaluate and analyze the interactions between the vibratory tools of construction equipments and the terrain. Non‐linear static and dynamic characteristics are the basic model defined properties. Elastic, dissipative and plastic rheological components were included into the main model. Partial concluding remarks have shown a good approximation between numerical results and experiments. The results of this study are very useful for vibratory equipment designing and correct exploitation, check of Regulations conformity for construction technologies, and oldies equipments maintenance. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carmen Debeleac; Silviu Nastac. On Non-linear Characteristics Evaluation of Vibratory Tool and Terrain Interaction for Embankment Works. PAMM 2012, 12, 605 -606.
AMA StyleCarmen Debeleac, Silviu Nastac. On Non-linear Characteristics Evaluation of Vibratory Tool and Terrain Interaction for Embankment Works. PAMM. 2012; 12 (1):605-606.
Chicago/Turabian StyleCarmen Debeleac; Silviu Nastac. 2012. "On Non-linear Characteristics Evaluation of Vibratory Tool and Terrain Interaction for Embankment Works." PAMM 12, no. 1: 605-606.
This paper deals with the theoretical aspects combined with experimental analysis regarding early damage identification in passive vibro-isolation devices. Basically, this research presents the relevant results obtained for a singular element. Rubber based on elements is discussed especially. This study was a naturally fall-back of the authors large analysis regarding the dynamic behaviour of the passive isolation devices against vibration, shocks and seismic waves. Main hypothesis supposed that on the exploitation time, all technical devices and systems acquire different levels of wearing because of the dynamic overloads and their derivative influences (aging, fatigue, energy dissipation, external heating or cooling, etc.). Hereby the performance characteristics changes and the system becomes working improperly. Numerical simulations were developed for simple spatial configuration of isolation device. Stochastic approach of essential results was briefly presented nearby the relevant results and discussions.
A. Leopa; Silviu Nastac; Carmen Debeleac. Researches on Damage Identification in Passive Vibro-Isolation Devices. Shock and Vibration 2012, 19, 803 -809.
AMA StyleA. Leopa, Silviu Nastac, Carmen Debeleac. Researches on Damage Identification in Passive Vibro-Isolation Devices. Shock and Vibration. 2012; 19 (5):803-809.
Chicago/Turabian StyleA. Leopa; Silviu Nastac; Carmen Debeleac. 2012. "Researches on Damage Identification in Passive Vibro-Isolation Devices." Shock and Vibration 19, no. 5: 803-809.