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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 existing literature provides various computational models related to the dynamic behavior of strand wire ropes. It starts from the simple longitudinally oscillating beam, to the complex nonlinear multi-body configuration based on helical structural symmetry. The challenge is the prior availability of characteristic parameters for material behavior, structural configuration, and functional capability. Experimental investigation is the main source for evaluation of these characteristics. However, tests have specifically been performed according to each case, minimizing the generalization aspect. This is the main frame of this study. Hereby, the authors propose an ensemble of spectral investigations, applied to a reduced set of experimental tests regarding wire rope dynamics. The research goal consists of wire rope characterization in terms of the flexible and adaptive groups of parameters, related to the conservative and dissipative behaviors. An experimental setup is considered here according to the rope exploitation conditions in order to enable an extension of the method application from the experimental mode to the operational mode. Experiments are conducted based on classical vibration measurement procedures. The analysis is performed using a spectral method ensemble, including discrete Fourier transform, time-frequency joint analysis, and the Prony method. The result show that the proposed assessments can provide suitable information related to a large group of wire rope models.
Gina Diana Musca (Anghelache); Carmen Debeleac; Sorin Vlase. Experimental Assessments on the Evaluation of Wire Rope Characteristics as Helical Symmetrical Multi-body Ensembles. Symmetry 2020, 12, 1231 .
AMA StyleGina Diana Musca (Anghelache), Carmen Debeleac, Sorin Vlase. Experimental Assessments on the Evaluation of Wire Rope Characteristics as Helical Symmetrical Multi-body Ensembles. Symmetry. 2020; 12 (8):1231.
Chicago/Turabian StyleGina Diana Musca (Anghelache); Carmen Debeleac; Sorin Vlase. 2020. "Experimental Assessments on the Evaluation of Wire Rope Characteristics as Helical Symmetrical Multi-body Ensembles." Symmetry 12, no. 8: 1231.
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 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.
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.
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.
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.
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.
A highly efficient seismic protection of bridges have been demonstrated by the passive control systems with mechanical links with selective viscoelastic energy dissipation through viscous friction and dry friction. These systems are able to take over the deformations and movements caused by temperature variations, those due to seismic activities and from road traffic. A number of natural factors such as atmospheric and anthropogenic parameters, such as shock and vibration from road traffic, lead to the degradation of the viscoelastic bonds of passive control systems based on rubber molding. The presence of the elastic and dissipative nonlinear forces in the functioning of antiseismic systems inevitably leads to quantitative and qualitative changes of the structural responses of bridges and viaducts both in time and spectral domains. The implications of these changes on the integrity and stability of the bridge or viaduct sections may be from the simplest to the most severe depending on the type of seismic excitation to which they are subjected. For these reasons, it is imperative that we should identify and quantify the degree of nonlinearity of antiseismic systems embedded in the structure of bridges and viaducts in order to prevent accidents with severe socioeconomic implications. In this way can determine the dependence of the nonlinear behavior of the bearing system and the degree of degradation of their viscoelastic links. From a theoretical point of view the following parameters of the vibration of the system will be comparatively analyzed: the displacement and acceleration of the bridge deck in time and frequency domains, the hysteretic loop, the representation in the plane of phases, the power spectral density and the spectrograms of the acceleration signals. From an experimental point of view there will be identified and plotted the parameters able to provide information regarding the abnormal operation of the bearings from the elastomer: system acceleration, representations in time and frequency and its spectrogram.
A. Leopa; Silviu Nastac; Carmen Debeleac. Numerical and Experimental Testing of Normality in the Functioning of the Bearings System. Shock and Vibration 2012, 19, 915 -928.
AMA StyleA. Leopa, Silviu Nastac, Carmen Debeleac. Numerical and Experimental Testing of Normality in the Functioning of the Bearings System. Shock and Vibration. 2012; 19 (5):915-928.
Chicago/Turabian StyleA. Leopa; Silviu Nastac; Carmen Debeleac. 2012. "Numerical and Experimental Testing of Normality in the Functioning of the Bearings System." Shock and Vibration 19, no. 5: 915-928.