Ovidiu Vasile

• PhD
• Assoc. Prof. Dr. Habil. at Universitatea Națională de Știință și Tehnologie Politehnica București

In this paper, it is proposed a systematic presentation of the known methods for determining the elastic constants of a composite material using the vibration response. For a series of bodies with a simple shape, the value of the eigenfrequencies for different boundary conditions can be calculated with the standard formula (for example for beams, p...

The Maxwell rheological behavior of materials with a high content of fluid fraction with very fine particles in the mixture leads to the predominant character of the viscous component in series connection with the elastic component. For this, laboratory tests were carried out on small-scale samples subjected to a variable-frequency vibrating regime...

The experimental research carried out under forced vibrations, by applying a harmonic excitation inertial force, highlighted the fact that the processed viscoelastic materials, when put into operation (fresh concrete, soil, asphalt mixes, filling mastics, mortar with additives, bitumens), can be characterized by a relevant dynamic response that cor...

The results of the research on the monotonically increasing change in the stiffness of the Voigt-Kelvin viscoelastic materials correspond to real dynamic regimes in the field of vibration compaction technologies. Thus, the models identified by the Voigt-Kelvin schematization both in the laboratory and in situ regarding foundation soils, concretes o...

The global population is expected to increase by nearly 2 billion individuals over the next three decades, leading to a significant surge in waste generation and environmental challenges. To mitigate these challenges, there is a need to develop sustainable solutions that can effectively manage waste generation and promote a circular economy. Myceli...

In this paper a new analytical solution for solving the issues that arise in determining the correct form of the eigenmodes, for the case of simply supported on two opposite edges and clamped on the other two of a rectangular plate, is described. The case of a homogenous plate, isotropic, with constant thickness and uniformly distributed weight, an...

Starting from the need to determine the deformability of the inertial platform from the Research Facility of ELI-NP in Magurele-Bucharest in case of changing the position of some very heavy partition walls, a vibration study of the entire inertial platform was made. The research team studied various aspects of this issue and some of the results wer...

In this paper a new analytical solution for solving the issues that arise in determining the correct form of the eigenmodes, for the case of simply supported on two opposite edges and clamped on the other two of a rectangular plate, is described. The case of a homogenous plate, isotropic, with constant thickness and uniformly distributed weight, an...

The paper presents the physical model and the mathematical model of a mechanical system modeled as a solid body with 6 degrees of dynamic freedom and elastic bearings. Considering that the system has constructive symmetries (masses and inertia, elastic support elements), simpler physical and mathematical models are obtained, the systems of differen...

In addition to elastomeric devices, viscous fluid dampers can reduce the vibration transmitted to dynamic systems. Usually, these fluid dampers are rate-independent and used in conjunction with elastomeric isolators to insulate the base of buildings (buildings, bridges, etc.) to reduce the shocks caused by earthquakes by increasing the damping capa...

Sound-absorbing panels made with a perforated front and a sound-absorbing material on the back have been used in many forms of construction for a long time. It is a reasonably efficient system, obtaining high values of sound absorption at a specific resonant frequency, depending on the design of the structure of the sound-absorbing multilayer panel...

The aim of this work is to obtain new materials with improved sound absorbing and thermal properties, using rigid or flexible polyurethane foam reinforced with recycled fir sawdust from wood processing as well as by optimizing their mixing ratio. In this respect, we prepared and characterized samples by mixing rigid polyurethane foam (RPUF)/flexibl...

This paper studies the vibration of the inertial platform developed in Magurele-Bucharest, in the frame of the ELI-NP project. Two main components of this project are positioned on a concrete inertial insulating platform: a very high intensity laser system (10–30 PW) and a very brilliant, intense gamma beam (19 meV). This paper analyzes the behavio...

The paper reveals the experimental research carried out, in the anechoic chamber at the department of mechanics of University POLITEHNICA of Bucharest, to high-lite the noise reduction (the acoustic attenuation) from the source (S) to the receiver (R), using different material layers for the noise barrier. The tests were performed on an experimenta...

Featured Application Time–history analysis (THA), the Lyapunov Exponents Approach (LEA), and the Poincaré Map (PM) are enhanced to investigate the dynamic instability of forced torsional vibrations (FTV) for a double tripod industrial driveshaft (DTID) in transition through the principal parametric resonance region (PPRR). Based on a modified desig...

The aim of this paper is to propose ecological thermal insulation materials that meet the goals of sustainability but also fulfill the imposed thermal performance requirements. This paper studies new composite materials based on sheep wool from the perspective of thermal conductivity. The composites were prepared using two types of binder: acrylic-...

The paper addresses the methodology for obtaining biocomposite structures from waste, with sound-absorbing properties, such as: thuja shells, walnut shells, pistachio shells, beech sawdust, pumpkin seeds shells and sunflower seeds shells. The experimental analysis carried out considers the study of the sound-absorbing properties held by the propose...

Featured Application The asymptotic method approach (AMA) is used to compute the amplitudes of forced bending vibrating (FBV) movements versus the excitation frequency in the region of principal parametric resonance (PPR) for multibody mechanical systems. An FBV movements model was designed for an automotive driveshaft to realize a powerful design...

Sustainable materials made from recycled materials are an alternative to traditional materials (synthetic ones) and present a lower environmental impact. Due to the fact that natural fibers were successfully used to produce environmentally friendly sound adsorbing materials, biocomposites made from recycled polypropylene (PPR), feathers flour (FF)...

The aim of this research is to provide a better prediction for noise attenuation using thin rigid barriers. In particular, the paper presents an analysis on four methods of computing the noise attenuation using acoustic barriers: Maekawa-Tatge formulation, Kurze and Anderson algorithm, Menounou formulation, and the general prediction method (GPM-IS...

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Plant fibres are materials that can increase energy savings, and they are being analysed for their reduced environmental impact. In this paper, three types of multi-layered panels were developed as environmentally friendly flax fibre-based products for building industry applications. The structural build-up of the panels is such that one layer of w...

Circular economy and waste recycling are a priority domain in European policies. In the case of glass fiber reinforced polymer (GFRP), waste storage is prohibited; therefore, alternative options are encouraged: thermal, chemical, or mechanical recycling and comprehensive recovery. If thermal and chemical recycling are more suitable for carbon fiber...

In the paper are presented the results of tests on the evaluation of the level of noise and chemical air pollution in two distinct urban areas: an industrial area and an area characterized by heavy road traffic, with a focus on the novelty elements introduced by the regulations in force on the measurement and management of the level of ambient and...

The aim of this paper is to propose a novel sandwich panel, which would be suitable for sound absorption and airborne sound insulation, used as applied cladding or independent lightweight partition wall. As far as the authors are concerned, this is the first sheep wool-based sandwich panel using only natural materials. The structure was prepared us...

In recent years, natural materials are becoming a valid alternative to traditional sound absorbers due to reduced production costs and environmental protection. This study explores alternative usage of sheep wool as a construction material with improved sound absorbing properties beyond its traditional application as a sound absorber in textile ind...

Polyurethane foam wastes is one of the environmental problems for which are not still the efficient solutions of valorization. This paper presents the possibility of recovering polyurethane foam waste by obtaining some new materials with sound absorption properties. The polyurethane foam wastes were ground and mixed, in proportion of 0, 3, 5, 7 and...

We present in this paper a statistical method to estimate the severity of a transverse crack form the free-end deflections of a cantilever beam. To this aim, we carry out simulations involving the ANSYS software and register the free-end deflections resulted for different crack positions near the fastened end. By involving a statistical method, we...

The paper aims to present research on the determination of the coefficient of acoustic absorption as a function of frequency, for composite monolayer plates (made of: MDF - wooden dried agglomerated fibres with medium density, RWB - rebated wood from dried beech, PS - extruded polystyrene) and multilayer (with outer coatings of: MDF, RWB and polyme...

The paper presents the study of the vibrational behavior of laminated composites whose sheets are debonded but still in contact. The aim is to show that the delamination occurring in a given region of the structure produces different frequency shifts for the different bending vibration modes, dependent on the position and extent of the delamination...

The acoustic comfort includes the protection against noise and it is closely related to the sound absorption concept. This paper presents an experimental study on sound absorption coefficients, for some composite materials: waste materials (rubber crumbs, textile, flax fibers) mixed with rigid polyurethane foam as binder. The composite materials we...

This paper presents the determining of natural frequencies of plates without and with damages using the finite element method of SolidWorks program. The first thirty natural frequencies obtained for thin rectangular rectangular plates clamped on contour without and with central damages a for different dimensions. The relative variation of natural f...

The aim of the paper is to analyze the free vibration of a symmetrical, spatial structure made up of bars, obtained by joining two identical subsystems. It is a real structure, encountered in civil engineering. In the literature, there are papers that have established vibration properties of structures with symmetry. In the paper, we propose to see...

Pollution, in all its current views, is a permanent concern of the researchers. Therefore, making sound-absorbing materials that include waste is a very useful approach. The paper deals with two environment related issues: noise pollution due to different sources in industry and transport, as well as waste storage, also affecting the quality of the...

Lightweight structures made of composite materials are increasingly used in many industrial fields for high-technology applications due to their versatile property profile. Waste wood cause both health and environmental problems and this has forced governments to develop laws for recycling. Using fir sawdust in the domain of soundproofing materials...

In present, learning through experiments is the preferred studying method for students. Theoretical notions by experimental example offer a high level of understanding on phenomena. Virtual labs represent a method that ensures achieving high performance in designing tool machine. After familiarizing students with theoretical aspects, using Java app...

This paper comes to bring ways of harnessing the noise reduction properties of textile waste in the workplace. Noise reduction from the production sections can be achieved by encapsulating the noise source, mainly the engine and transmission to the components of work using plates of material in simple structure or composite structure. By testing mu...

Based on experimental measurements, this paper presents the vibration analysis of a hydro generator that equips a Kaplan hydraulic turbine of a Hydropower plant in Romania. This analysis means vibrations measurement to different operating regimes of the hydro generator respectively before installing it and into operation, namely putting off load mo...

This paper studies the acoustic performance of an acoustic resonator used for noise reduction, using numerical modelling for an open side-branches acoustic resonators. Plane waves were at the base of the transfer matrix method (TMM), which can provide a fast prototype solution for designers of acoustic resonators. In this paper are presented the pr...

The paper discusses the approach to harmonizing the analytical and practical action system with dynamic system that shapes the different categories of vehicles with electric motors. It aims to optimize the physical conditions to achieve significant operational regimes. It shows the parameters operated at resonance in correlation with damping ratio.

The paper analyzes the dynamic response of leaning against viscoelastic systems by composed model Hooke - Voigt Kelvin on outside action given by a harmonic force. Thus, are established analytical relations for linear viscoelastic composed model its purpose of determining significant parameters: The amplitude of vibration, transmitted forces on fix...

This paper present a numerical method of reducing the amplitude of the vibrations at the base due to vibrations produced by inertial forces in the case of mechanical equipment with adaptive systems feedback on adaptive algorithms. The basic idea is to introduce a new linear component, a controlled disturbing force, produced by a linear actuator or...

The paper analyzes the possibility of determining the acoustic absorption coefficient by means of mathematical models from the literature for new composite porous materials. The materials studied were made of fir sawdust and flexible polyurethane foam with open pores. The acoustic absorption coefficient of the materials was determined experimentall...

The aim of this study is to characterize the acoustical behavior of concrete made with crumb rubber waste from sport fields. Concrete mixes with different water to cement ratio (0.45, 0.50 and 0.55) and crumb rubber dosages (0%, 5.0% and 7.5% by weight) were prepared. Properties examined for the nine mixes included compressive strength, apparent de...

p>For sustainable development of the textile industry must find solutions to reduce waste and decrease noise at work. Of textile waste are obtained boards of different thicknesses, which aim to be wide field of use. For it is to achieve some experimental results about the soundproofing of plate types: is studying recoverable boards made of short te...

Plates known as sound absorbing materials: textiles recovered fabrics plus polyethylene are made layered composite material intended to be used to encapsulate industrial engines, as sources of noise in the production departments. Influence of thickness sound-absorbing material can be supported by the values obtained for the absorption coefficient,...

Noise is a well known source of environmental pollution in urban areas or at work. Sound pressure level has a harmful effect on human health. In this paper we present our research on making a new type of composite material and testing its properties of noise attenuation level. Tests were carried out in the anechoic chamber using barrier attenuators...

Polyurethane foam is an outstanding material for various applications. It is manufactured by propelling liquid isocyanate-polyol mixture to form foams in the presence of a blowing agent. This paper comprises an experimental study on acoustic properties improvement of rigid polyurethane closed-cell foam, by incorporating various quantities of textil...

In this article we obtained some experimental results about soundproofing of three types of stratified composite materials made of: plate of short fiber fabricated from recovered textile which joins with: cork board; expanded polyethylene, laminated on one side with aluminum foil of 9μm thickness or extruded polystyrene. These materials used in the...

Plates known as sound absorbing materials: textiles recovered fabrics plus polyethylene are made layered composite material intended to be used to encapsulate industrial engines, as sources of noise in the production departments. Influence of thickness sound-absorbing material can be supported by the values obtained for the absorption coefficient,...

The ultrasonic nondestructive evaluation of structural integrity of pipes in high risk industries such as chemical or nuclear, represents a domain of highest importance. The inspection of kilometers of piping in rough conditions is a difficult if not an impossible task. Guided ultrasonic waves can propagate however along tens of meters in pipes and...

Having as starting point the fundamental requirements outlined in Directive 2002/44/CE in which the minimum health and safety requirements for the workers’ exposure to the risks generated by physical agents (vibrations) are established, the paper presents a concrete evaluation, based on experimental determinations, of the vibrations transmitted to...

In this paper an analysis regarding the dynamics of thin rectangular plates embedded on all edges is presented; aiming to highlight the effect of defects upon their natural frequencies. The first thirty natural frequencies were obtained for a plate without defect and the same plate with four different types of defect. It was placed in the corner of...

In this paper the distortion of the neutral axis of cantilever beams due to damage is analyzed via numerical simulations. Both static and dynamic behaviors are considered, aiming to prove that the damage affects all bending vibration modes in a similar manner. Thus, the beam deflection under its own mass is identified for the healthy state and for...

The purpose of the paper is to show the results of both inductive and resistive damping in pressure acoustics for two different geometrical situations. Depending of the geometry, the reflective or resistive elements will have one or more eigenfrequencies with maximum attenuation. This study represents an investigation of the COMSOL Finite Elements...

For sustainable development of the textile industry we must found solutions for decrease waste and reducing noise in the workplace. For this we obtained some experimental results about soundproofing of two types of plates: a plate is made of textile recoverable with short fiber and the second plate is made of cork. Both materials have a thickness o...

This paper comprises an introductive part, in which theoretic notions regarding plates and their classification are presented, as well as stating some national and international researches published regarding the study and computing of plates. Also, there are described the defining parameters of the plate behavior, the mechanic and physic character...

In this paper, according to the natural frequencies resulted from the simulation for 30 vibration mode shapes of rectangular, square, trapeze and parallelogram plates that are analyzed with the SolidWorks program, the absolute respectively the relative variation has been obtained for thin clamped plates with the same area. The absolute and relative...

Research presented in this paper are focused on determining the acoustic performance of some composite materials made from textile waste as raw materials and polyurethane foam as binder. Negative effects of pollution intensified research on acoustic materials based on renewable resources, which can lead to viable alternatives to conventional materi...

The paper presents the simulation results of a booster-ultrasonic horn assembly. The ultrasonic horn shape is exponential and for the analyzed assembly was chosen different materials. Such an ultrasonic horn can be used in the composition of an experimental stand for experimental development of cavitation erosion of materials. By simulating the ent...

This paper presents an analytical model for a mechanical system with three masses and a disruptive force applied to one of them. It presents an analysis of the free vibration, the vibration eigenmodes and forced vibration. Finally, there are several experimental determinations on a stand with three masses set with two elastic metal blades, made by...

The behavior of a molecular architecture into an isotropic heat field was analyzed considering the thermodynamic properties of fermionic oscillators. Beginning with the grand canonical ensemble and the thermodynamic potential we could describe two major contributions: a trigonometric function responsible for selective energy accumulation under...

Ultrasonic piezoelectric transducers used in classical nondestructive testing are producing in general longitudinal vibrations in the MHz range. A simple mechanical model of these transducers would be very useful for wave propagation numerical simulations, avoiding the existing complicated models in which the real components of the transducer are m...

Noise is a 'non-periodic sounds' complex which affects biological and psychological state of people and other natural organisms. The present paper is dedicated to some new polymeric composites with sound-absorbing properties. The originality consists in obtaining new polymeric composites from formaldehyde resin and various waste types used as reinf...

An algorithm to assess transversal cracks in composite structures based on natural frequency changes due to damage is proposed. The damage assessment is performed in two steps; first the crack location is found, and afterwards an evaluation of its severity is performed. The technique is based on a mathematical relation that provides the exact solut...

The paper addresses the topic of the inconsistency between experimental, laboratory results for antiseismic devices and the dynamic stiffness, internal damping and dissipation parameters through additional devices. The necessary corrections of the stiffness and dissipation (damping) parameters will be presented when the antiseismic devices are equi...

This paper aims to introduce new systems for absorption and attenuation of noise based on oxide composite materials made from recycled solid waste. Compared to conventional materials this new type of composites incorporates various wastes that can harm the environment. The absorption coefficient is used to express the capacity of a material to abso...

The guided ultrasonic waves have become interesting alternatives to classical pulse-echo nondestructive testing in industrial piping systems. These guided waves have the capability to travel for several meters along pipes, bringing back to the emitting transducer information about possible defects. For this reason, researches were conducted in many...

This paper investigates the acoustic performance of a reactive silencer for two special cases using numerical and experimental techniques. The plane waves based models such as the transfer matrix method (TMM) or boundary element method (BEM) can offer fast initial prototype solutions for silencer designers, hi this paper, the principles of TMM and...

This paper aims to introduce new systems for absorption and attenuation of noise based on oxide composite materials made from recycled solid waste. Compared to conventional materials this new type of composites incorporates various wastes that can harm the environment. The absorption coefficient is used to express the capacity of a material to abso...

This paper presents research on determining the sound absorption coefficient and structural damping level, for five samples, thus determining the sound absorption capacity and antivibrational propriety of each obtained material. Materials were made from particles of recycled rubber, fir sawdust and a polyurethane binder, in combination with other m...

Noise is a 'non-periodic sounds' complex which affects biological and psychological state of people and other natural organisms. The present paper is dedicated to some new polymeric composites with sound-absorbing properties. The originality consists in obtaining new polymeric composites from formaldehyde resin and various waste types used as reinf...

In this paper are presented researches on the identification of factors that influence the sound absorption coefficient of porous materials used for absorption of the sound wave. To achieve these researches were used three materials (glass wool, flexible polyurethane foam and rigid polyurethane foam) for which it was determined the sound absorption...

The paper presents a study of dynamic real machine consists of an engine and body work, using a dynamic equivalent scheme to a system of two discs linked to each other by an elastic element. Is performed an analysis of the transient regime applying a constant torque on the disc of the motor influence also a constant braking torque on the motor driv...

Rezumat Lucrarea abordează comportarea unui model de solid-rigid cu anumite simetrii structurale. Aceste simetrii permit simplificarea calculelor (ecuaţii de mişcare) şi, deci, a modelelor matematice. Dacă solidul rigid este conectat la structură prin patru legături elastice, modelul rămâne încă simplu şi uşor de rezolvat, vibraţiile putând fi decu...

The results of the experimental tests, in dynamic regime, on antiseismic elastomeric devices, evidenced the fact that the internal damping represents a significant parameter tightly related to the specific shearing deformation of the elastomeric elements. Consequently, based on the final obtained results, correlation curves were raised meant to rep...

The paper presents the experimental results regarding the hysteretic behavior of elastomeric systems made in conformity with the European Standards SR EN 1337-3 and SR EN 15129. It is also mentioned that the hysteretic damping was determined by experimentally raising the hysteresis loop in a low-cycle harmonic regime, with a kinematic exterior exci...

The paper presents the main antiseismic devices, as component elements of the base isolation systems, in such a manner that the functional and constructive parameters are correlated with the inertial and stiffness characteristics of the dynamic isolated building. Also, each device will be characterized through a rheological model, which conditions...