Article
Engineering, Mechanical
Elia Iseli, Jurg Schiffmann
Summary: The forced response of rigid rotors, supported by herringbone-grooved gas journal bearings, is investigated numerically and experimentally. The effects of center of mass position and static loading on rotor motion are studied.
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
(2022)
Article
Engineering, Mechanical
Jan Rendl, Miroslav Byrtus, Stepan Dyk, Lubos Smolik
Summary: This work investigates the impact of forces due to rotating unbalance and pressure gradients in the oil film on rotating machinery supported on journal bearings. The analysis focuses on the sub-synchronous motion of a rigid rotor supported on cylindrical journal bearings at rotor speeds lower than the threshold speed for oil whirl. It is found that sub-synchronous vibration can occur before reaching the threshold speed and that the underlying period-doubling bifurcation depends on the amount of rotating unbalance. The rotor response and stability are analyzed using a numerical continuation method and validated through time simulations.
NONLINEAR DYNAMICS
(2023)
Article
Engineering, Mechanical
S. Boedo
Summary: This study investigates the impact of surface ellipticity on self-acting partial arc journal bearings under steady load and sinusoidal oscillation, taking into account mass conserving cavitation. The computational efficiency is improved by using a generalized Warner bearing (GWB) formula. The results demonstrate that an elliptical sleeve can significantly improve bearing performance at small oscillation amplitudes commonly found in practical applications, and a fully hydrodynamic lubrication regime can be established through the wearing-in process of the sleeve surface.
TRIBOLOGY INTERNATIONAL
(2022)
Article
Engineering, Mechanical
M. R. Pattnayak, J. K. Dutt, R. K. Pandey
Summary: This paper presents the dynamics of an accelerating rotor supported on Aerodynamic Journal Bearings in high-speed micro-turbomachines. By planning suitable acceleration schedules, the whirl amplitude and frequency can be limited to low levels.
TRIBOLOGY INTERNATIONAL
(2022)
Article
Engineering, Electrical & Electronic
Guglielmo Giannetti, Enrico Meli, Andrea Rindi
Summary: Tilting pad journal bearings (TPJBs) are important components in modern rotating machines. This study proposes an innovative modeling approach based on efficient flexible multibody techniques to describe the behavior of TPJBs. The model is tested on a real TPJB geometry and validated through experimental tests, showing encouraging results. The proposed model can be applied in various engineering fields such as Oil & Gas and aeronautics.
Article
Acoustics
Lubos Smolik, Jan Rendl, Milan Omasta, Miroslav Byrtus, Petr Sperka, Pavel Polach, Martin Hartl, Michal Hajzman
Summary: This paper investigates the effects of mechanically induced textures on the stability of journal bearings, focusing on lightly loaded bearings commonly used in vertical rotors and microturbines. The results show that textures near the minimum oil film thickness can improve stability at low loads, but have little effect at a specific load of 0.15 MPa. The paper also discusses computational methods for dealing with cavitation and highlights the sensitivity of numerical results to the density of computational mesh.
JOURNAL OF SOUND AND VIBRATION
(2023)
Article
Engineering, Mechanical
Faisal Rahmani, J. K. Dutt, R. K. Pandey
Summary: Conventional oil lubricated journal bearings are impractical at high temperatures, so powder lubricants can be used instead. Surface modifications in the form of pockets in the bearing can improve performance and different pocket shapes have an impact on the rotor stability, with rectangular shape being the most effective.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE
(2021)
Article
Mechanics
Hussein Sayed, T. A. El-Sayed
Summary: Investigating the dynamics and stability of flexible rotors supported by journal bearings is crucial in designing efficient and reliable rotating machines. This study examines a model of a flexible rotor supported by two symmetric journal bearings. The nonlinear bearing forces are evaluated using either a direct solution of the Reynolds equation or analyzing it to obtain linear and nonlinear bearing stiffness and damping coefficients. These coefficients are obtained for different operating conditions and bearing parameters. The results are validated with previous literature and a perturbation analysis is used to investigate the validity range of the bearing coefficients. A novel technique based on polynomial fitting is used to represent the bearing coefficients as a function of the bearing parameters, enabling the study of the dynamics of the flexible rotor model using numerical continuation techniques. The effect of bearing design parameters on system stability, such as groove angle, length to diameter ratio, and static pressure, is also investigated.
INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS
(2022)
Article
Chemistry, Multidisciplinary
Luis San Andres, Jing Yang, Andrew Devitt
Summary: Gas film bearings enable high-speed oil-free (micro) rotating machinery with gains in efficiency, reliability, longer maintenance intervals, and a reduction in contaminants released to the atmosphere. Among gas bearing types, porous surface gas bearings (PGBs) have proven to be successful mechanical elements for over 50 years, and their performance can be predicted using analytical and finite-element models.
APPLIED SCIENCES-BASEL
(2021)
Article
Engineering, Mechanical
Eduardo Afonso Ribeiro, Diogo Stuani Alves, Katia Lucchesi Cavalca, Carlos Alberto Bavastri
Summary: This study proposes a mathematical model that combines analytical calculation of oil-film coefficients, fractional derivative approach for the viscoelastic materials dynamics, and generalized equivalent parameters for dynamically modeling hybrid oil-bearing-viscoelastic-support systems. Through simulations, it is shown that viscoelastic supports improve the stability of rotating systems, and optimization can enhance vibration suppression characteristics of the device.
MECHANISM AND MACHINE THEORY
(2021)
Article
Engineering, Mechanical
Leonardo Urbiola-Soto, Paolo Pennacchi
Summary: This paper presents component and system-level analyses on the effects of stiffness, damping, and rotor stability of tilting pad journal bearings with assembled clearance variation. It is found that the variation in clearance leads to significant differences in stiffness and damping, but has negligible impact on rotor stability.
JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME
(2022)
Article
Chemistry, Multidisciplinary
Jisu Park, Donghee Kim, Kyuho Sim
Summary: The study investigates the rotordynamic stability of journal gas foil-polymer bearings (GFPBs) in a dual-rotor bearing system. The results show that GFPBs have better stability performance compared to GFBs in terms of delaying and suppressing unstable vibrations. GFPBs are reliable lubricating elements that can dampen vibrations in machines operating at relatively low temperatures.
APPLIED SCIENCES-BASEL
(2022)
Article
Engineering, Mechanical
Yihua Wu, Lin An, Kai Feng, Yuanlong Cao, Hanqing Guan
Summary: This study experimentally investigated the dynamic responses of a rigid rotor supported with two HPTPBs, successfully achieving rotor acceleration at high speeds. Tests with different unbalance mass and supply pressure ratios showed that the prediction model aligned well with experimental results, providing a possibility for rotor support in high-speed Turbomachinery.
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
(2022)
Article
Engineering, Mechanical
Robin M. Robrecht, Peter F. Pelz
Summary: The present study investigates the influence of the Lomakin effect on stationary bearing performance and proposes a new model that accounts for fluid inertia. The results demonstrate the crucial role of accurately treating the Lomakin effect for prediction accuracy.
TRIBOLOGY INTERNATIONAL
(2022)
Article
Engineering, Mechanical
Mohammad Hojjati, H. M. Navazi, Hassan Haddadpour
Summary: This paper investigates the nonlinear vibrations of a rigid two-dimensional rotor supported on tilting-pad-journal-bearing under harmonic excitation using a nonlinear quadratic model and second-order multiple scales method. The frequency response function, the effect of excitation force on the response, and system stability are discussed, showing potential hardening or softening behavior under different operating conditions. The solution may be multivalued depending on initial conditions, with the possibility of jump phenomena.
JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING
(2021)
Article
Engineering, Mechanical
Antonella Castellano, Pietro Stano, Umberto Montanaro, Marco Cammalleri, Aldo Sorniotti
Summary: This paper proposes a new control strategy for hybrid electric vehicles, called Model Predictive Control (MPC), and considers the losses in transmission gears. Through a case study on Chevrolet Volt, the results show that the simplified internal model has a minor impact on fuel consumption performance.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Rui Peng, Gregory S. Chirikjian
Summary: This article introduces a method of designing morphable thick-panel origami structures using reconfigurable linkages, which improves the potential of origami techniques for different tasks and solves the limitations of one-DOF and multiple-DOF folding structures.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Gaohan Zhu, Weizhong Guo, Yinghui Li, Youcheng Han
Summary: Comprehensive and accurate performance evaluation is crucial for profile synthesis and analysis of higher pair mechanisms. This paper proposes evaluation indices and methods for the transmission performance of planar higher pair mechanisms from different perspectives. It subdivides the transmission performance into element-based performance and joint-based performance and develops novel indices specific to higher pair mechanisms. A graphical mapping method based on element-based performance is also proposed for intuitive analysis. Practical examples validate the effectiveness of the proposed indices and methods for evaluating the performance of higher pair mechanisms.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Ke Wu, Gang Zheng, Guimin Chen, Shorya Awtar
Summary: Researchers proposed a new modeling method, namely Body-frame Beam Constraint Model (BBCM), to predict and optimize the design of high-precision compliant mechanisms (CMs).
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Youcheng Han, Weizhong Guo, Changjie Zhao, Ziyue Li, Ze Fu, Yinghui Li
Summary: This study proposes a structural synthesis methodology that considers motion, force, and energy characteristics simultaneously to design efficient mechanisms.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Cristian Enrico Capalbo, Daniel De Gregoriis, Tommaso Tamarozzi, Giuseppe Carbone, Domenico Mundo
Summary: This study proposes a novel flexible multibody formulation that enables efficient updating of models while maintaining small size and high accuracy. Numerical validation demonstrates its wide applicability across various materials and mechanisms, showing promising results in terms of accuracy.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Weihao Zhao, Junbei Liao, Wei Qian, Haoyong Yu, Zhao Guo
Summary: This paper presents a newly designed compliant actuator using a tensile springs array to address the challenges in achieving linear and consistent elastic properties, low friction, minor hysteresis, and good compliance in series elastic actuators (SEA). The unique geometry of the spring array enables the SEA to have consistent rotary stiffness with minimal friction and hysteresis. The device's performance is evaluated using PID and sliding mode control, demonstrating its constant low rotary stiffness and torque tracking bandwidth, making it suitable for human-robot interaction requirements.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Mohui Jin, Yukang Luo, Xing Xu, Bowei Xie, Weisheng Wang, Zewei Li, Zhou Yang
Summary: This paper presents a method for evaluating the contact interaction between compliant mechanisms and external objects. By establishing a numerical model and introducing contact springs to describe the contact forces, the deformation and normal contact force/stress can be accurately calculated. The static equilibrium configuration and contact force/stress can be obtained by minimizing the total potential energy function of the system.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Alejandro G. Gallardo, Martin A. Pucheta
Summary: This paper presents a method for the synthesis of parallel flexure systems using Screw Theory and Linear Algebra. The method is validated through three case studies and offers a simple and precise design with decoupled actuators.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Xiao Wang, Chenglin Liu, Haoxiang Sun, Hanwen Song
Summary: This paper presents a new decomposition mode for robot-world calibration, which decomposes the Ad(SE(3)) equation using Chasles' motion. A two-step method based on point set matching is proposed. The superiority of this method is verified through simulations and experiments.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Yanlin Chen, Xianmin Zhang, Yanjiang Huang, Yanbin Wu, Jun Ota
Summary: This study establishes an error model for a 3-RRR+UR spherical parallel mechanism and analyzes the sensitivity of error parameters. A design structure is proposed to reduce input errors based on the analysis. Experimental results show that the multiloop circuit incremental method provides more accurate results.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Vu Linh Nguyen, Chin-Hsing Kuo, Po Ting Lin
Summary: This paper presents a method for analyzing the performance of gravity-balanced serial robotic manipulators under dynamic loads and uses a three-degree-of-freedom planar serial manipulator as a case study. The significance of this method is demonstrated by evaluating the impact of dynamic loads on gravity-balanced performance and proposing a step-by-step design procedure to improve it.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Shifeng Rong, Jiange Zhang, Xing Zhang, Keliang Li, Kaibin Rong, Zhenyu Zhou, Han Ding
Summary: This article proposes a data-driven dry cutting tool collaborative optimization model to improve the economic and environmental attributes of facehobbing hypoid gears. An innovative ease-off tooth contact analysis method is introduced to establish accurate relations between ease-off flank and loaded contact performance evaluations. The proposed model significantly improves sustainability in terms of economic and environmental assessments.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Kemal Eren, Soley Ersoy, Ettore Pennestri
Summary: This research investigates the instantaneous kinematics of the terminal link of a planar two-link open chain using the complex-number technique and higher-order instantaneous invariants.
MECHANISM AND MACHINE THEORY
(2024)
Article
Engineering, Mechanical
Bo Han, Zhantu Yuan, Jiachuan Zhang, Yundou Xu, Jiantao Yao, Yongsheng Zhao
Summary: This paper proposes novel deployable mechanism units with self-limiting position function, and constructs ring truss deployable mechanisms. The degrees of freedom (DOF) of deployable units are analyzed and it is proved that the constructed ring truss deployable mechanisms have only one DOF. The dynamic model of the deployable mechanism unit with passive actuation is established and verified by simulation. The deployable mechanism units proposed in this paper have the advantages of good scalability and stability, and have broad application prospects.
MECHANISM AND MACHINE THEORY
(2024)
