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MOSLEM MOLAIE EMAMZADEH

CULTORE DELLA MATERIA
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2023 - Spiral Bevel Gears: nonlinear dynamic model based on accurate static stiffness evaluation [Articolo su rivista]
Molaie, Moslem; Samani, Farhad S.; Zippo, Antonio; Pellicano, Francesco
abstract

In the present paper non-linear dynamics of a spiral bevel gear pair with backlash are investigated in order to clarify the internal excitations of major importance from the vibration point of view: manufacturing errors in the teeth profile, teeth spacing errors, and elastic deformation of the teeth. In some conditions, like in the case of backside contact, the destructive effect of internal excitations can be intensified leading to complex dynamics; for such reasons here backside contacts and reverse rotation are investigated in detail using a nonlinear time-varying model. The effect of damping is investigated as well. A one-DOF model is developed in order to study the dynamic behavior; the resulting a nonlinear differential equation with time-varying mesh stiffness is solved via numerical integration based on an adaptive step-size implicit Runge-Kutta scheme. The dynamic response of the system is analyzed through time histories, phase portraits, bifurcation diagrams, and Poincaré maps. Results show that for small backlash values, the possibility of backside contact increases. Meanwhile, by increasing the backlash value, the amplitude vibration of the gear rotation rises as well. By comparing the dynamic response of the system with different damping ratios, the results show that higher damping effectively reduces gear vibration resonance, although the probability of unsteady response still exists.

2022 - Digital Twins: Neural-Networks for the implementation of digital twins of gearboxes [Relazione in Atti di Convegno]
Zippo, A.; Bergamini, L.; D'Elia, G.; Pellicano, F.; Dalpiaz, G.; Iarriccio, G.; Molaie, M.
abstract

2022 - Effects of laser surface texturing on the dynamic performance of spur gears [Relazione in Atti di Convegno]
Iarriccio, G.; Zippo, A.; Molaie, M.; Bergamini, L.; Pellicano, F.
abstract

Laser Surface Texturing (LST) has been successfully applied to improve the tribological performance of reciprocating surfaces. In this context, although the relative motion between the meshing teeth is a combination of sliding and rolling, gears provided with LST could further reduce losses and vibrations in power transmissions. In this study, experimental results on the efficiency and the vibrations of gears are reported. The tests were carried out through a test bench that allows for evaluating the power losses of the transmission and the dynamic transmission error thanks to a set of torquemeters and accelerometers. Different load and speed conditions were investigated, and a comparison of the results between textured gears and standard carburized gears is provided.

2022 - Experiments on a Quasi-zero Stiffness Suspension for Passive Vibration Control [Relazione in Atti di Convegno]
Iarriccio, G.; Molaie, M.; Zippo, A.; Pellicano, F.
abstract

Experimental measurements on a quasi-zero stiffness (QZS) isolator under base excitations are reported. The setup is described and the QZS isolator is compared to a standard mass-spring system. The role of the geometric nonlinearities on the dynamic behavior is clear: the QZS isolator transmissibility shows a natural frequency reduction, and the system effectively suppresses the ground vibration about the fundamental frequency of the standard system. The QZS isolator performance has been tested also under real earthquake signals, showing satisfactory acceleration mitigation.

2022 - Loaded and unloaded tooth contact analysis of spiral bevel gears in consideration of misalignments [Articolo su rivista]
Moslem, M.; Zippo, A.; Iarriccio, G.; Bergamini, L.; Pellicano, F.
abstract

Bevel gear pairs are employed extensively in transmission systems, such as vehicle transmissions (rear axle drive), aircraft engines/turbines and helicopter gears, to transfer power between non-parallel shafts at high speed or high torque. The most complex form of bevel gear is the spiral bevel gear (SBG). SBG pairs are commonly used in applications that require high load capacity at higher operating speeds than are typically possible with other types of bevel gear. When manufactured in a metal-cutting process, spiral bevel gears can either be produced using single indexing (a face-milling method, which is considered in this study) or continuous indexing (a face-hobbing method). Due to manufacturing imperfections and the flexibility of components, the system might experience misalignments that intensify or exert a destructive effect on the gear vibration, which causes disruption in the stress distribution, thereby decreasing the lifetime of the gearbox. The main purpose of this study is to carry out loaded tooth contact analysis (LTCA) and unloaded tooth contact analysis (UTCA) for an SBG pair in the presence of two types of misalignment, axial and radial misalignment, and represent their effects on the mesh stiffness (MS). To calculate the MS, it is essential to determine the geometrical mismatch between two mating tooth profiles by means of UTCA. To conduct LTCA, three main approaches can be utilised: the finite element method (FEM) and experimental and analytical approaches. Due to the development of software packages during the last decade, Transmission3D-Calyx, an FEM-based software, is used in this study to carry out LTCA and UTCA. Finally, the MS for different misalignment cases is compared to represent the effect of misalignment on the SBG pair.

2022 - Planet Load-Sharing and Phasing [Articolo su rivista]
Molaie, M.; Deylaghian, S.; Iarriccio, G.; Samani, F. S.; Zippo, A.; Pellicano, F.
abstract

2021 - Gear prognostics: A predictive algorithm for lifetime estimation of operating gearboxes [Abstract in Atti di Convegno]
Bergamini, L.; Zippo, A.; Pellicano, F.; Iarriccio, G.; Molaie, M.
abstract

For the realization of optimized, effective gearboxes, both the set of design rules and the study of operation conditions, interconnected to each other, have to be taken into account. Condition monitoring is an essential tool when study of gearbox operation is tackled, and many techniques have been developed to detect the onset and the development of wear. However, these techniques fall short when prediction of gearbox conditions is concerned, as in the case of tracking the useful lifetime during operation. Within this framework, a prognostic software is developed and presented. This software is able to estimate the useful lifetime of a gearbox on the base of design features (safety factors and parameters), standards and codes (ISO) and realistic/measured load spectra, representative of the operation condition of the gearbox. This tool opens up the possibility of combining condition monitoring and prediction for a wider, comprehensive study of gearbox operation. Moreover, it potentially allows to detect machinery misuse and plan accurate usage-dependent maintenance in industrial environment.

2021 - Nonlinear vibration of the spiral bevel gear under periodic torque considering multiple elastic deformation evaluations due to different bearing supports [Articolo su rivista]
Samani, Farhad S.; Moein, Salajegheh; MOLAIE EMAMZADEH, Moslem
abstract

This paper investigates two parameters effect on vibrational responses of the spiral bevel gear. Changing the gear system overall stiffness (GSOS) considering elastic deformation and periodic torques are the two parameters which are represented as the main goals of this study. In order to investigate the effects of shaft stiffness and elastic deformation, two different cases with different support locations are considered. The first case is presented by locating the support close to the gear, and in the latter one, the distance between gear and support is increased. Besides, to study the effect of torque, two main types are considered: constant and periodic excitation torque. To illustrate the dynamic behavior, the governing differential equations are solved numerically according to the Runge-Kutta method. The equations are nonlinear due to backlash and time-varying coefficients as the results of GSOS variation. Vibrational phenomena are illustrated by means of bifurcation diagrams, RMS, and Poincare maps. Particular vibrational behaviors such as "chaos" and "period-doubling" phenomena are illustrated with details. By investigating the effect of shaft stiffness, results show that when the support is far away from gear, the vibration response increased by 67.5%. Moreover, while the input torque is constant, the support movement does not cause undesirable responses such as chaotic or period-doubling responses. The periodic torque causes undesirable responses such as chaos and bifurcation and period-doubling responses.

2019 - Nonlinear vibration of crowned gear pairs considering the effect of Hertzian contact stiffness [Articolo su rivista]
MOLAIE EMAMZADEH, Moslem; Samani, Farhad S.; Habibollah, Motahar
abstract

This study aims to analyze the influence of lead crowning modification of teeth on the vibration behavior of a spur gear pair. Two dynamic rotational models including an uncrowned and crowned gear are examined. Hertzian mesh stiffness is computed using tooth contact analysis in quasi-static state along a complete mesh cycle of teeth mesh. The dynamic orbits of the system are observed using some useful attractors which expand our understanding about the influence of crown modification on the vibration behavior of the gear pair. Nonlinear impact damper consists of non-integer compliance exponents identify energy dissipation of the system beneath the surface layer. By augmenting tooth crown modification, the surface penetration increases and consequently normal pressure of the contact area becomes noticeable. Finally, the results show modification prevents gear pair to experience period doubling bifurcation as the numerical results proved. Using this new method in dynamic analysis of contact, broaden the new horizon in analyzing of the surface of bodies in contact.

2019 - Nonlinear vibration of the spiral bevel gear with a novel tooth surface modification method [Articolo su rivista]
S. Samani, Farhad; Molaie, Moslem; Pellicano, Francesco
abstract

The issue of gear noise is fairly common in power transmission systems. This noise largely stems from the gear pairs vibration triggered by transmission error excitation. This is mainly caused by tooth profile errors, misalignment and tooth deflections. This research endeavors to examine nonlinear spiral bevel gears vibration with the innovative method of tooth surface modification. To design spiral bevel gears with the higher-order transmission error (HTE), the non- linear vibration of a novel method is investigated. The meshing quality of the HTE spiral bevel gears, as the results demonstrate, sounds more suitable than of the meshing quality gears. Their design was made by means of the parabolic transmission error (PTE). The maximum time response root mean square of the HTE method decreases by 44% concerning the PTE method. The peak-to-peak of the transmission error is decreased by 35% via HTE overall frequency range. However, HTE method is not able to decrease the vibration level on all frequency ratios.

2018 - Autofrettage of nonlinear strain-hardening cylinders using the proposed analytical solution for stresses [Articolo su rivista]
MOLAIE EMAMZADEH, Moslem; Darijani, H.; Bahreman, M.; Hosseini, S. M.
abstract

This paper focuses on pressurized thick-walled cylinders with nonlinear strain-hardening behavior. At first, a constitutive model is proposed to capture the test data done on the steel specimen. It is shown that this model is able to cover the various specific behaviors such as the perfect plastic, linear hardening, and nonlinear hardening behaviors. This constitutive model due to high performance in constitutive modeling and simplicity of its mathematical form is applied to pressurized thick-walled cylinders in order to find a closed-form analytical solution for their analysis. For this purpose, elasto-plastic stresses distribution in pressurized thick-walled cylinders made of a nonlinear strain-hardening material is obtained analytically for both loading and unloading phases using Tresca's yield criterion and considering the Bauschinger effect. Then, the solution is compared with experimental data and good agreement between predicted results and experimental data is observed. In the following, the residual stresses distribution are obtained to determine the best level of autofrettage for strengthening and design of these thick-walled cylinders prior to industrial use with the aim of increasing strength-to-weight ratio. It was observed that the parameters such as the material behavior (stress strain curve) and the Bauschinger effect have a significant influence on the results.

2016 - Nonlinear vibration of the bevel gear with teeth profile modification [Articolo su rivista]
Motahar, H.; Samani, F. S.; Molaie, Moslem
abstract

The prediction of gear vibration and noise has always been a major concern in gear design. Noise and vibration are inevitable problems that are involved in transmission systems; they have intensified when some nonlinear phenomena such as jump phenomenon, tooth separation and period-doubling bifurcation appear in the system. Tip and/or root modifications are well-known solutions that improve dynamic performance of gears. The present work investigates the complex, nonlinear dynamic behavior of three bevel gear models: (1) model with pure involute profile, (2) model with statically optimized tooth profile, and (3) model with dynamically optimized tooth profile. Tooth profile modification is employed in models by means of genetic algorithm in order to extract the best amount and length of modifications. The dynamic responses obtained from dynamic analyzer were compared qualitatively and quantitatively. By augmenting tooth profile modification, the average value of the dynamic responses is decreased intensely for both statically and dynamically optimized gear pairs. Dynamic load factor is calculated and compared with the involute tooth profile model and the two optimized gear sets. Employing teeth optimization leads to elimination of period- (Formula presented.) in both optimized simulations.

2015 - Application of linear and nonlinear vibration absorbers for the nonlinear beam under moving load [Articolo su rivista]
Afshar, N. P.; Samani, F. S.; Molaie, Moslem
abstract

Recently, a large amount of studies have been related to nonlinear systems with multi-degrees of freedom as well as continuous systems. The purpose of this paper is to optimize passive vibration absorbers in linear and nonlinear states for an Euler-Bernoulli beam with a nonlinear vibratory behavior under concentrated moving load. The goal parameter in the optimization is maximum deflection of the beam. The large deformation for beam modeling is considered, i.e. the relation between strains and deflections is nonlinear. The force magnitude and beam length are two effective factors for the beam deflection. Vibration absorber with linear damping and linear or nonlinear stiffness is also considered in this manuscript. The results show that, for normal forces and short beams, linear and nonlinear models have similar behaviors, while surveying nonlinear behavior is necessary by increasing the force and length of the beam, i.e. large deflections. Moreover, the difference between linear and nonlinear beam models for regular force magnitudes and beam lengths is negligible. For higher loads and longer beams, beam model nonlinearity can be important. Results demonstrate that,in the presented numerical values (train bridge application) for cubic nonlinear vibration absorber, there are two optimal locations for vibration absorber installation: one inclined from the middle of the beam to the direction of moving loads and the second which is more interestingly inclined from the middle of the beam to moving loads in the opposite direction. Moreover, depending on the model's numerical parameters, for short beams, linear vibration absorber is more effective, while for long beams, cubic nonlinear beam behaves better than the linear one.