This article attempts to analyze the Hopf bifurcati on behavior of a railway wheelset in the pres... more This article attempts to analyze the Hopf bifurcati on behavior of a railway wheelset in the presence of dead-zone and yaw damper nonlinearities. A model that is more precise than Yang and Ahmadian is investigated. Using Bogoliubov-Mitropolsky averaging method and critical speed, the amplitude of the limit cycle in the presence of the mentioned nonlinearities is taken into consideration. To solve these nonlinear equations analytically, the integration interval has been divided into three sub-domains. Two-dimensional bifurcation diagrams are provided to illustrate the mechanism of formation of Hopf bifur cation. These diagrams can be used for design of stable wheelset systems.
Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics
This work is a study on transient vibrational behaviour of a vehicle driveline system during tip-... more This work is a study on transient vibrational behaviour of a vehicle driveline system during tip-in/released/tip-out throttle. The considered vehicle is a passenger sedan, front-wheel drive, front-engine equipped with a four-stroke four-cylinder SI engine and a 5-speed manual transmission. The engine's model follows the mean value model including the effects both dynamics and combustion parameters including manifold/engine volume, air to fuel ratio, spark advance/retard and RPM on its transient indicator and brake torque behaviour. A primary fourteen-degrees-of-freedom lumped parameter torsional driveline model including, a multi-staged clutch with nonlinear clutch springs model and the gear backlash effect on idle as well as engaged gears is considered. This model is reduced to a six-degrees-of-freedom model. A rigid 2D model and magic formula are used for modelling of vehicle-tyre-road dynamics interaction. Using the overall model, the role of the driving style, the engine dyn...
In this study, a hybrid method is proposed to investigate the nonlinear vibrations of pre- and po... more In this study, a hybrid method is proposed to investigate the nonlinear vibrations of pre- and post-buckled rectangular plates for the first time. This is an answer to an existing need to develope a fast and precise numerical model which can handle the nonlinear vibrations of buckled plates under different boundary conditions and plate shapes. The method uses the differential quadrature element, arc-length, harmonic balance and direct iterative methods. The governing differential equations of plate vibration have been extracted considering shear deformations and the initial geometric imperfection. The solution is assumed to be the sum of the static and dynamic parts which upon inserting them into the governing equations, convert them into two sets of nonlinear differential equations for static and dynamic behaviors of the plate. First, the static solution is calculated using a combination of the differential quadrature element method and an arc-length strategy. Then, putting the fir...
The effects of initial geometric imperfection and pre- and post-buckling deformations on vibratio... more The effects of initial geometric imperfection and pre- and post-buckling deformations on vibration of isotropic rectangular plates under uniaxial compressive in-plane load have been studied. The differential equations of plate motions, using the Mindlin theory and Von-Karman stress-strain relations for large deformations, were extracted. The solution of nonlinear differential equations was assumed as the summation of dynamic and static solutions. Due to a large static plate deflection as compared with its vibration amplitude, the differential equations were solved in two steps. First, the static equations were solved using the differential quadrature method and the arc-length strategy. Next, considering small vibration amplitude about the deformed shape and eliminating nonlinear terms, the natural frequencies were extracted using the differential quadrature method. The results for different initial geometric imperfection and different boundary conditions reflect the impact of the me...
Journal of Applied Mechanics and Technical Physics, 2015
This paper exhibits the effect of the amplitude of vibrations on the pull-in instability and nonl... more This paper exhibits the effect of the amplitude of vibrations on the pull-in instability and nonlinear natural frequency of a double-sided actuated microswitch by using a nonlinear frequency-amplitude relationship. The nonlinear governing equation of the microswitch pre-deformed by an electric field includes even and odd nonlinearities with a quintic nonlinear term. The study is performed by a new analytical method called the Hamiltonian approach (HA). It is demonstrated that the first term in series expansions is sufficient to produce an acceptable solution. Results obtained by numerical methods validate the soundness of the asymptotic procedure.
Volume 7: Dynamic Systems and Control; Mechatronics and Intelligent Machines, Parts A and B, 2011
... Behrooz Attaran Graduate student, Department of Mechanical Engineering, Shahid Chamran Univer... more ... Behrooz Attaran Graduate student, Department of Mechanical Engineering, Shahid Chamran University Ahvaz, Khouzestan, Iran attaranbehrooz@yahoo.com ... Acta Mechanica Solida Sinica, Vol. 19, No. 4, December (2006). [2] S. Ali A. Moosavian, Rambod Rastegari, Multiple ...
This paper presents the advantages of some effective analytical approaches applied on the governi... more This paper presents the advantages of some effective analytical approaches applied on the governing equation of transversely vibrating cantilever beams. Six studied methods are Min-Max Approach, Parameter Expansion Method, Hamiltonian Approach, Variational Iteration Method, Bubnov-Galerkin and Energy Balance Method. The powerful analytical approaches are used to obtain frequency-amplitude relationship for dynamic behavior of nonlinear vibration of cantilever beams. It is demonstrated that one term in series expansions of all methods are sufficient to obtain a highly accurate solution. Finally, a numerical example is conducted to verify the accuracy of these methods.
The present study focuses on the nonlinear analysis of the dynamical behavior of layered structur... more The present study focuses on the nonlinear analysis of the dynamical behavior of layered structures, including interfacial friction in the presence of the stick-slip phenomenon and large deformation. To achieve a proper outlook for the two-layer structure's behavior, it is essential to precisely realize the mechanisms of motion. Taking the dry friction into account, coupled equations of the transversal and longitudinal large vibration of two-layers are derived and nondimensionalized. Furthermore, the free and forced vibration of the aforementioned system is investigated. From the results of the numerical simulation, it is observed that there exist quasi-periodic and stick–slip chaotic motions in the system. The results demonstrate that the single mode method usually utilized may lead to incorrect conclusions and, instead, the higher order mode method should be employed. A comparative study with ANSYS is developed to verify the accuracy of the proposed approach.
This article attempts to analyze the Hopf bifurcati on behavior of a railway wheelset in the pres... more This article attempts to analyze the Hopf bifurcati on behavior of a railway wheelset in the presence of dead-zone and yaw damper nonlinearities. A model that is more precise than Yang and Ahmadian is investigated. Using Bogoliubov-Mitropolsky averaging method and critical speed, the amplitude of the limit cycle in the presence of the mentioned nonlinearities is taken into consideration. To solve these nonlinear equations analytically, the integration interval has been divided into three sub-domains. Two-dimensional bifurcation diagrams are provided to illustrate the mechanism of formation of Hopf bifur cation. These diagrams can be used for design of stable wheelset systems.
Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics
This work is a study on transient vibrational behaviour of a vehicle driveline system during tip-... more This work is a study on transient vibrational behaviour of a vehicle driveline system during tip-in/released/tip-out throttle. The considered vehicle is a passenger sedan, front-wheel drive, front-engine equipped with a four-stroke four-cylinder SI engine and a 5-speed manual transmission. The engine's model follows the mean value model including the effects both dynamics and combustion parameters including manifold/engine volume, air to fuel ratio, spark advance/retard and RPM on its transient indicator and brake torque behaviour. A primary fourteen-degrees-of-freedom lumped parameter torsional driveline model including, a multi-staged clutch with nonlinear clutch springs model and the gear backlash effect on idle as well as engaged gears is considered. This model is reduced to a six-degrees-of-freedom model. A rigid 2D model and magic formula are used for modelling of vehicle-tyre-road dynamics interaction. Using the overall model, the role of the driving style, the engine dyn...
In this study, a hybrid method is proposed to investigate the nonlinear vibrations of pre- and po... more In this study, a hybrid method is proposed to investigate the nonlinear vibrations of pre- and post-buckled rectangular plates for the first time. This is an answer to an existing need to develope a fast and precise numerical model which can handle the nonlinear vibrations of buckled plates under different boundary conditions and plate shapes. The method uses the differential quadrature element, arc-length, harmonic balance and direct iterative methods. The governing differential equations of plate vibration have been extracted considering shear deformations and the initial geometric imperfection. The solution is assumed to be the sum of the static and dynamic parts which upon inserting them into the governing equations, convert them into two sets of nonlinear differential equations for static and dynamic behaviors of the plate. First, the static solution is calculated using a combination of the differential quadrature element method and an arc-length strategy. Then, putting the fir...
The effects of initial geometric imperfection and pre- and post-buckling deformations on vibratio... more The effects of initial geometric imperfection and pre- and post-buckling deformations on vibration of isotropic rectangular plates under uniaxial compressive in-plane load have been studied. The differential equations of plate motions, using the Mindlin theory and Von-Karman stress-strain relations for large deformations, were extracted. The solution of nonlinear differential equations was assumed as the summation of dynamic and static solutions. Due to a large static plate deflection as compared with its vibration amplitude, the differential equations were solved in two steps. First, the static equations were solved using the differential quadrature method and the arc-length strategy. Next, considering small vibration amplitude about the deformed shape and eliminating nonlinear terms, the natural frequencies were extracted using the differential quadrature method. The results for different initial geometric imperfection and different boundary conditions reflect the impact of the me...
Journal of Applied Mechanics and Technical Physics, 2015
This paper exhibits the effect of the amplitude of vibrations on the pull-in instability and nonl... more This paper exhibits the effect of the amplitude of vibrations on the pull-in instability and nonlinear natural frequency of a double-sided actuated microswitch by using a nonlinear frequency-amplitude relationship. The nonlinear governing equation of the microswitch pre-deformed by an electric field includes even and odd nonlinearities with a quintic nonlinear term. The study is performed by a new analytical method called the Hamiltonian approach (HA). It is demonstrated that the first term in series expansions is sufficient to produce an acceptable solution. Results obtained by numerical methods validate the soundness of the asymptotic procedure.
Volume 7: Dynamic Systems and Control; Mechatronics and Intelligent Machines, Parts A and B, 2011
... Behrooz Attaran Graduate student, Department of Mechanical Engineering, Shahid Chamran Univer... more ... Behrooz Attaran Graduate student, Department of Mechanical Engineering, Shahid Chamran University Ahvaz, Khouzestan, Iran attaranbehrooz@yahoo.com ... Acta Mechanica Solida Sinica, Vol. 19, No. 4, December (2006). [2] S. Ali A. Moosavian, Rambod Rastegari, Multiple ...
This paper presents the advantages of some effective analytical approaches applied on the governi... more This paper presents the advantages of some effective analytical approaches applied on the governing equation of transversely vibrating cantilever beams. Six studied methods are Min-Max Approach, Parameter Expansion Method, Hamiltonian Approach, Variational Iteration Method, Bubnov-Galerkin and Energy Balance Method. The powerful analytical approaches are used to obtain frequency-amplitude relationship for dynamic behavior of nonlinear vibration of cantilever beams. It is demonstrated that one term in series expansions of all methods are sufficient to obtain a highly accurate solution. Finally, a numerical example is conducted to verify the accuracy of these methods.
The present study focuses on the nonlinear analysis of the dynamical behavior of layered structur... more The present study focuses on the nonlinear analysis of the dynamical behavior of layered structures, including interfacial friction in the presence of the stick-slip phenomenon and large deformation. To achieve a proper outlook for the two-layer structure's behavior, it is essential to precisely realize the mechanisms of motion. Taking the dry friction into account, coupled equations of the transversal and longitudinal large vibration of two-layers are derived and nondimensionalized. Furthermore, the free and forced vibration of the aforementioned system is investigated. From the results of the numerical simulation, it is observed that there exist quasi-periodic and stick–slip chaotic motions in the system. The results demonstrate that the single mode method usually utilized may lead to incorrect conclusions and, instead, the higher order mode method should be employed. A comparative study with ANSYS is developed to verify the accuracy of the proposed approach.
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Papers by Kourosh Heidari Shirazi