This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Vibrating plates produce noise, which is of high interest in many technical applications. In most... more Vibrating plates produce noise, which is of high interest in many technical applications. In most cases such plate vibrations have relatively large amplitudes and only a nonlinear von Kármán type model can be used. The rectangular plate vibrations are determined both numerically and experimentally. The first aim is to identify the parameters of the real boundary conditions, which are elastically clamped. The control parameters are elastic bending stiffness of the four edges of the plate as functions of vibration amplitude. Influences of actuator amplitude and excitation position on the plate are presented. Using the optimized model, spatial sound directivity diagrams are determined, based on a numerical procedure. Experiments in the anechoic chamber are used to further improve the model. By identification of various parameters, a better control of plate noise radiation is achieved.
The increased interest for improved gear design has led to extensive research into the field of n... more The increased interest for improved gear design has led to extensive research into the field of nonlinear dynamics of such systems. The paper reveals a complex dynamic model to study the behavior in a gearpair system taking into consideration backlash and time-dependent mesh stiffness and mesh damping. In many applications including turbo machinery, machine tools and diesel engines non-linearities are present due to tooth stiffness, damping and backlash that induced micro-vibrations of non-linear parametric type. In the mean time the input link of the driver ax and the output link of the driven ax induce non-linearities. The paper presents the use of asymptotic method in order to compute the phase angle of steady state motion. By this way the paper reveals the phenomena's characteristics of multiple jumps specific to the non-linear dynamic behavior of gear-pair due to: non-linearities of the input-output linkages, backlash and self-induced parametric excitations, caused by the tooth stiffness and damping. It was highlighted the interaction between fundamental resonance and the principal parametric resonance.
The increased interest for improved gear design has led to extensive research into the field of n... more The increased interest for improved gear design has led to extensive research into the field of nonlinear dynamics of such systems. The paper reveals a complex dynamic model to study the behavior in a gearpair system taking into consideration backlash and time-dependent mesh stiffness and mesh damping. In many applications including turbo machinery, machine tools and diesel engines non-linearities are present due to tooth stiffness, damping and backlash that induced micro-vibrations of non-linear parametric type. In the mean time the input link of the driver ax and the output link of the driven ax induce non-linearities. The paper presents the use of asymptotic method in order to compute the phase angle of steady state motion. By this way the paper reveals the phenomena's characteristics of multiple jumps specific to the non-linear dynamic behavior of gear-pair due to: non-linearities of the input-output linkages, backlash and self-induced parametric excitations, caused by the tooth stiffness and damping. It was highlighted the interaction between fundamental resonance and the principal parametric resonance.
The paper reveals the vibrations of a wagon with two bogies having elastic links and dampers betw... more The paper reveals the vibrations of a wagon with two bogies having elastic links and dampers between the wagon box and the bogie and also between the wheels and the bogie. The entire system has two vertical planes of symmetry therefore the models has 15 d.o.f.. The railway is considered elastic solid in both planes horizontal and vertical that induces forced vibrations of the wagon. The vibrations are studied using the Language's equations and the Hamilton's principle. By this way it was found for the first time a mathematical approach for the wagon box forced vibrations in connection with the non-linear vibrations of the rail. In the mean time the authors found, by using the Hamilton's principle and the Dirac function, two partial derivatives equations which describe the forced non-linear vibrations at the rail in two planes namely: vertical and horizontal.
Journal of the Acoustical Society of America, Feb 1, 1999
This paper presents a model for the acoustic emission of a circular plate, in the domain of large... more This paper presents a model for the acoustic emission of a circular plate, in the domain of large deflections. The thin circular plate is considered homogeneous, isotropic, and fixed on the boundaries. In the hypothesis of large displacements, the nonlinear von-Karman dynamic model was adopted. The external action is periodic and axisymmetric. An approximate analytical method was developed, based on the Kantorovich method and the asymptotic method, to compute the dynamic response of the plate. Starting from the characteristic parameters of the nonlinear vibrations of the plate, a model of acoustic emitter based on the Rayleigh formulation was developed, to obtain the acoustical pressure and the spatial directivity characteristic. Experimental tests were developed in an anechoic chamber, in order to confirm the model. The physical model of the plate consists of a circular frame having a high rigidity and a brass plate of 0.2-mm width. In the transverse direction, passing through the mass center of the plate, it acts as an excitatory device and the acoustic emission of the plate is analyzed. In this way, the natural frequencies of the plate and the spatial directivity characteristic have been determined and a satisfactory agreement with the theoretical results has been found.
International Conference on Applied Mathematics, Mar 22, 2007
Mufflers are widely used for exhaust noise attenuation in vehicles, machinery and other industria... more Mufflers are widely used for exhaust noise attenuation in vehicles, machinery and other industrial elements. Modeling procedures for accurate performance prediction had led to the development of new methods for practical muffler components in design. Plane wave based models such as the transfer matrix method (TMM) can offer fast initial prototype solutions for muffler designers. In the present paper the authors present an overview of the principles of TMM for predicting the transmission loss (TL) of a muffler. The predicted results agreed in some limits with the experimental data published in literature.
International Conference on Applied Mathematics, Nov 1, 2006
Mufflers are widely used for exhaust noise attenuation in vehicles, machinery and other industria... more Mufflers are widely used for exhaust noise attenuation in vehicles, machinery and other industrial elements. Modeling procedures for accurate performance prediction had led to the development of new methods for practical muffler components in design. Plane wave based models such as the transfer matrix method (TMM) can offer fast initial prototype solutions for muffler designers. In the present paper the authors present an overview of the principles of TMM for predicting the transmission loss (TL) of a muffler. The predicted results agreed in some limits with the experimental data published in literature.
The vibroacoustic signals emitted by the diarthrodial articulation during a normal movement diffe... more The vibroacoustic signals emitted by the diarthrodial articulation during a normal movement differentiates a healthy case from a pathologic one, due to alteration in forms and contact surfaces. The differences are shown by a various dynamics of the vibroacoustic spectra. Parametric representation of the acquired signals, filtering and clinical interpretation of those allow classification and fast recognition of a normal/pathologic status of the investigated articulation by the physician. Our method of acquiring the sound and vibration signals is effectuated completely non-invasive, with a set of translators using Pulse - sounds and vibrations analyzers (a matrix of prepolarised microphones with measurement domain in infrasound scale and piezoelectric acceleration transducers). A comparative study of vibroacoustic and thermal spectra, with early alterations revealed by knee nuclear magnetic resonance, correlates vibroacoustic and thermic spectra alterations with morphological ones, by determining certain limits between normal and pathological morphofunctional patterns. This prospective comparative study will help us evaluate the method in terms of sensibility, specificity, negative and positive predictive value, indices that assure the diagnostic power to the method.
International Conference on Applied Mathematics, Nov 1, 2006
The paper reveals recent developments of the influence of the geometric imperfections on the ampl... more The paper reveals recent developments of the influence of the geometric imperfections on the amplitude of the non-linear vibrations of thin rectangular plates parametrically excited. In the region of principal parametric resonance, starting from the temporal non-linear differential equation that describes the oscillatory movement and using the second order approximation of the asymptotic method was computed the amplitude as function of system parameters and geometric imperfections. By varying the intensity of the geometric imperfections was obtained their influence upon the amplitude for the stationary non-linear dynamic response.
Romanian journal of internal medicine = Revue roumaine de médecine interne, 2006
The vibroacoustic signals emitted by the diarthrodial articulation during a normal movement diffe... more The vibroacoustic signals emitted by the diarthrodial articulation during a normal movement differentiates a healthy case from a pathologic one, due to alteration in forms and contact surfaces. The differences are shown by a various dynamics of the vibroacoustic spectra. Parametric representation of the acquired signals, filtering and clinical interpretation of those allow classification and fast recognition of a normal/pathologic status of the investigated articulation by the physician. Our method of acquiring the sound and vibration signals is effectuated completely non-invasive, with a set of translators using Pulse - sounds and vibrations analyzers (a matrix of prepolarised microphones with measurement domain in infrasound scale and piezoelectric acceleration transducers). A comparative study of vibroacoustic and thermal spectra, with early alterations revealed by knee nuclear magnetic resonance, correlates vibroacoustic and thermic spectra alterations with morphological ones, b...
In addition to elastomeric devices, viscous fluid dampers can reduce the vibration transmitted to... more 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 capability. According to the EN 15129 standard, the velocity-dependent anti-seismic devices are Fluid Viscous Dampers (FVDs) and Fluid Spring Dampers (FSDs). Based on experimental data from a dynamic regime of a fluid viscous damper of small dimensions, for which not all the design details are known, to determine the law of behavior for the viscous damper, the characteristics of the damper are identified, including the nonlinear parameter α (exponent of velocity V) of the constitutive law. Note that the magnitude of the fluid damper force depends on both velocity (where the maximum value is 0.52 m/s) and amplitude displacement (±25 mm). Using ...
Sound-absorbing panels made with a perforated front and a sound-absorbing material on the back ha... more 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 present work considers an acoustic panel in two constructive types, consisting of four layers: a front panel made of perforated sheet, polyethylene foam foil, basalt wool board with two different thicknesses, and a back panel of the non-perforated sheet. Due to the different thicknesses of the basalt wool board, for the multilayer structure of the acoustic panel, differences in acoustic impedance and acoustic absorption can be highlighted, experimentally determined with an impedance tube, using the transfer function method (TFM) based on EN ISO 10534-2 in the frequency range 100–3200 Hz. In the meantime, a method was developed to pre...
The present work aims to design a robust method to detect and certify the deterministic chaos or ... more The present work aims to design a robust method to detect and certify the deterministic chaos or ergodic process for the forced torsional vibrations (FTV) of a double tripod industrial driveshaft (DTID) in transition through the principal parametric resonance region (PPRR) which is considered by the researchers in the field as one of the most important resonance regions for the systems having parametric excitations. The DTID’s model for FTV considers the following effects: nonuniformities of inertial characteristics of the DTID’s elements, the harmonic torque excitation induced by the asynchronous electrical motor used for a heavy-duty grain mill, and the harmonic reaction torque generated by different granulation of the substance needed to be milled. Based on these aspects, a model of the FTV for the DTID was designed which was a modified, physically consistent model already used by the authors to investigate the FTV of automotive driveshafts (homokinetic transmission). For the DTI...
Featured Application: Time-history analysis (THA), the Lyapunov Exponents Approach (LEA), and the... more 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 designed model of FTV for an automotive driveshaft (AD), a robust method comprising THA, LEA, and PM (THA-LEA-PM) was created that certifies the existence of deterministic chaos or an ergodic process for the dynamic behavior of DTID's FTV in transition through PPRR. These methods represent a design tool for the DTID's FTV control of the homokinetic driveline transmission in the industry.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Vibrating plates produce noise, which is of high interest in many technical applications. In most... more Vibrating plates produce noise, which is of high interest in many technical applications. In most cases such plate vibrations have relatively large amplitudes and only a nonlinear von Kármán type model can be used. The rectangular plate vibrations are determined both numerically and experimentally. The first aim is to identify the parameters of the real boundary conditions, which are elastically clamped. The control parameters are elastic bending stiffness of the four edges of the plate as functions of vibration amplitude. Influences of actuator amplitude and excitation position on the plate are presented. Using the optimized model, spatial sound directivity diagrams are determined, based on a numerical procedure. Experiments in the anechoic chamber are used to further improve the model. By identification of various parameters, a better control of plate noise radiation is achieved.
The increased interest for improved gear design has led to extensive research into the field of n... more The increased interest for improved gear design has led to extensive research into the field of nonlinear dynamics of such systems. The paper reveals a complex dynamic model to study the behavior in a gearpair system taking into consideration backlash and time-dependent mesh stiffness and mesh damping. In many applications including turbo machinery, machine tools and diesel engines non-linearities are present due to tooth stiffness, damping and backlash that induced micro-vibrations of non-linear parametric type. In the mean time the input link of the driver ax and the output link of the driven ax induce non-linearities. The paper presents the use of asymptotic method in order to compute the phase angle of steady state motion. By this way the paper reveals the phenomena's characteristics of multiple jumps specific to the non-linear dynamic behavior of gear-pair due to: non-linearities of the input-output linkages, backlash and self-induced parametric excitations, caused by the tooth stiffness and damping. It was highlighted the interaction between fundamental resonance and the principal parametric resonance.
The increased interest for improved gear design has led to extensive research into the field of n... more The increased interest for improved gear design has led to extensive research into the field of nonlinear dynamics of such systems. The paper reveals a complex dynamic model to study the behavior in a gearpair system taking into consideration backlash and time-dependent mesh stiffness and mesh damping. In many applications including turbo machinery, machine tools and diesel engines non-linearities are present due to tooth stiffness, damping and backlash that induced micro-vibrations of non-linear parametric type. In the mean time the input link of the driver ax and the output link of the driven ax induce non-linearities. The paper presents the use of asymptotic method in order to compute the phase angle of steady state motion. By this way the paper reveals the phenomena's characteristics of multiple jumps specific to the non-linear dynamic behavior of gear-pair due to: non-linearities of the input-output linkages, backlash and self-induced parametric excitations, caused by the tooth stiffness and damping. It was highlighted the interaction between fundamental resonance and the principal parametric resonance.
The paper reveals the vibrations of a wagon with two bogies having elastic links and dampers betw... more The paper reveals the vibrations of a wagon with two bogies having elastic links and dampers between the wagon box and the bogie and also between the wheels and the bogie. The entire system has two vertical planes of symmetry therefore the models has 15 d.o.f.. The railway is considered elastic solid in both planes horizontal and vertical that induces forced vibrations of the wagon. The vibrations are studied using the Language's equations and the Hamilton's principle. By this way it was found for the first time a mathematical approach for the wagon box forced vibrations in connection with the non-linear vibrations of the rail. In the mean time the authors found, by using the Hamilton's principle and the Dirac function, two partial derivatives equations which describe the forced non-linear vibrations at the rail in two planes namely: vertical and horizontal.
Journal of the Acoustical Society of America, Feb 1, 1999
This paper presents a model for the acoustic emission of a circular plate, in the domain of large... more This paper presents a model for the acoustic emission of a circular plate, in the domain of large deflections. The thin circular plate is considered homogeneous, isotropic, and fixed on the boundaries. In the hypothesis of large displacements, the nonlinear von-Karman dynamic model was adopted. The external action is periodic and axisymmetric. An approximate analytical method was developed, based on the Kantorovich method and the asymptotic method, to compute the dynamic response of the plate. Starting from the characteristic parameters of the nonlinear vibrations of the plate, a model of acoustic emitter based on the Rayleigh formulation was developed, to obtain the acoustical pressure and the spatial directivity characteristic. Experimental tests were developed in an anechoic chamber, in order to confirm the model. The physical model of the plate consists of a circular frame having a high rigidity and a brass plate of 0.2-mm width. In the transverse direction, passing through the mass center of the plate, it acts as an excitatory device and the acoustic emission of the plate is analyzed. In this way, the natural frequencies of the plate and the spatial directivity characteristic have been determined and a satisfactory agreement with the theoretical results has been found.
International Conference on Applied Mathematics, Mar 22, 2007
Mufflers are widely used for exhaust noise attenuation in vehicles, machinery and other industria... more Mufflers are widely used for exhaust noise attenuation in vehicles, machinery and other industrial elements. Modeling procedures for accurate performance prediction had led to the development of new methods for practical muffler components in design. Plane wave based models such as the transfer matrix method (TMM) can offer fast initial prototype solutions for muffler designers. In the present paper the authors present an overview of the principles of TMM for predicting the transmission loss (TL) of a muffler. The predicted results agreed in some limits with the experimental data published in literature.
International Conference on Applied Mathematics, Nov 1, 2006
Mufflers are widely used for exhaust noise attenuation in vehicles, machinery and other industria... more Mufflers are widely used for exhaust noise attenuation in vehicles, machinery and other industrial elements. Modeling procedures for accurate performance prediction had led to the development of new methods for practical muffler components in design. Plane wave based models such as the transfer matrix method (TMM) can offer fast initial prototype solutions for muffler designers. In the present paper the authors present an overview of the principles of TMM for predicting the transmission loss (TL) of a muffler. The predicted results agreed in some limits with the experimental data published in literature.
The vibroacoustic signals emitted by the diarthrodial articulation during a normal movement diffe... more The vibroacoustic signals emitted by the diarthrodial articulation during a normal movement differentiates a healthy case from a pathologic one, due to alteration in forms and contact surfaces. The differences are shown by a various dynamics of the vibroacoustic spectra. Parametric representation of the acquired signals, filtering and clinical interpretation of those allow classification and fast recognition of a normal/pathologic status of the investigated articulation by the physician. Our method of acquiring the sound and vibration signals is effectuated completely non-invasive, with a set of translators using Pulse - sounds and vibrations analyzers (a matrix of prepolarised microphones with measurement domain in infrasound scale and piezoelectric acceleration transducers). A comparative study of vibroacoustic and thermal spectra, with early alterations revealed by knee nuclear magnetic resonance, correlates vibroacoustic and thermic spectra alterations with morphological ones, by determining certain limits between normal and pathological morphofunctional patterns. This prospective comparative study will help us evaluate the method in terms of sensibility, specificity, negative and positive predictive value, indices that assure the diagnostic power to the method.
International Conference on Applied Mathematics, Nov 1, 2006
The paper reveals recent developments of the influence of the geometric imperfections on the ampl... more The paper reveals recent developments of the influence of the geometric imperfections on the amplitude of the non-linear vibrations of thin rectangular plates parametrically excited. In the region of principal parametric resonance, starting from the temporal non-linear differential equation that describes the oscillatory movement and using the second order approximation of the asymptotic method was computed the amplitude as function of system parameters and geometric imperfections. By varying the intensity of the geometric imperfections was obtained their influence upon the amplitude for the stationary non-linear dynamic response.
Romanian journal of internal medicine = Revue roumaine de médecine interne, 2006
The vibroacoustic signals emitted by the diarthrodial articulation during a normal movement diffe... more The vibroacoustic signals emitted by the diarthrodial articulation during a normal movement differentiates a healthy case from a pathologic one, due to alteration in forms and contact surfaces. The differences are shown by a various dynamics of the vibroacoustic spectra. Parametric representation of the acquired signals, filtering and clinical interpretation of those allow classification and fast recognition of a normal/pathologic status of the investigated articulation by the physician. Our method of acquiring the sound and vibration signals is effectuated completely non-invasive, with a set of translators using Pulse - sounds and vibrations analyzers (a matrix of prepolarised microphones with measurement domain in infrasound scale and piezoelectric acceleration transducers). A comparative study of vibroacoustic and thermal spectra, with early alterations revealed by knee nuclear magnetic resonance, correlates vibroacoustic and thermic spectra alterations with morphological ones, b...
In addition to elastomeric devices, viscous fluid dampers can reduce the vibration transmitted to... more 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 capability. According to the EN 15129 standard, the velocity-dependent anti-seismic devices are Fluid Viscous Dampers (FVDs) and Fluid Spring Dampers (FSDs). Based on experimental data from a dynamic regime of a fluid viscous damper of small dimensions, for which not all the design details are known, to determine the law of behavior for the viscous damper, the characteristics of the damper are identified, including the nonlinear parameter α (exponent of velocity V) of the constitutive law. Note that the magnitude of the fluid damper force depends on both velocity (where the maximum value is 0.52 m/s) and amplitude displacement (±25 mm). Using ...
Sound-absorbing panels made with a perforated front and a sound-absorbing material on the back ha... more 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 present work considers an acoustic panel in two constructive types, consisting of four layers: a front panel made of perforated sheet, polyethylene foam foil, basalt wool board with two different thicknesses, and a back panel of the non-perforated sheet. Due to the different thicknesses of the basalt wool board, for the multilayer structure of the acoustic panel, differences in acoustic impedance and acoustic absorption can be highlighted, experimentally determined with an impedance tube, using the transfer function method (TFM) based on EN ISO 10534-2 in the frequency range 100–3200 Hz. In the meantime, a method was developed to pre...
The present work aims to design a robust method to detect and certify the deterministic chaos or ... more The present work aims to design a robust method to detect and certify the deterministic chaos or ergodic process for the forced torsional vibrations (FTV) of a double tripod industrial driveshaft (DTID) in transition through the principal parametric resonance region (PPRR) which is considered by the researchers in the field as one of the most important resonance regions for the systems having parametric excitations. The DTID’s model for FTV considers the following effects: nonuniformities of inertial characteristics of the DTID’s elements, the harmonic torque excitation induced by the asynchronous electrical motor used for a heavy-duty grain mill, and the harmonic reaction torque generated by different granulation of the substance needed to be milled. Based on these aspects, a model of the FTV for the DTID was designed which was a modified, physically consistent model already used by the authors to investigate the FTV of automotive driveshafts (homokinetic transmission). For the DTI...
Featured Application: Time-history analysis (THA), the Lyapunov Exponents Approach (LEA), and the... more 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 designed model of FTV for an automotive driveshaft (AD), a robust method comprising THA, LEA, and PM (THA-LEA-PM) was created that certifies the existence of deterministic chaos or an ergodic process for the dynamic behavior of DTID's FTV in transition through PPRR. These methods represent a design tool for the DTID's FTV control of the homokinetic driveline transmission in the industry.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Uploads
Papers by MIHAI BUGARU