The Experts below are selected from a list of 171 Experts worldwide ranked by ideXlab platform
Fulei Chu - One of the best experts on this subject based on the ideXlab platform.
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Dynamic modeling and analysis of the planetary gear under pitching base motion
International Journal of Mechanical Sciences, 2018Co-Authors: Xinghui Qiu, Qinkai Han, Fulei ChuAbstract:Abstract Planetary gear transmission is subjected to base motions in many industrial applications such as wind turbines and automobiles, and its Dynamic behavior will be affected by base motions. To develop a Dynamic model more suitable for the planetary gear under base motions, the general modeling procedures are illustrated in detail from the perspective of energy. A rotational-translational-Axial Dynamic model of the planetary gear under pitching base motion is proposed and validated. Pitching base motion causes additional damping, stiffness and forced excitation, which disrupts the force symmetry of the planetary gear and results in unequal load sharing. Dynamic responses of the planetary gear are obtained by numerical integration, and spectrum analysis is conducted using the Fourier transform. Spectra of the rotational and translational vibrations of the central components show completely different characteristics because of the structure symmetry of the planetary gear. The influences rules of parameters on response spectra and load sharing conditions are derived, including the amplitude and the frequency of the pitching base motion, and the carrier rotating speed. When the base excitation frequency approaches half the translational natural frequencies, the load sharing condition of the planetary gear will deteriorate rapidly. The load sharing factor increases by the square of the base excitation amplitude.
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load sharing characteristics of planetary gear transmission in horizontal axis wind turbines
Mechanism and Machine Theory, 2015Co-Authors: Xinghui Qiu, Fulei ChuAbstract:Abstract With the increase of wind turbine size, gravity becomes an important non-torque excitation source. Gravity disrupts the cyclic symmetry of the planetary gear and causes unequal load-sharing. Because of the specific operation conditions, the bedplate will tilt and lead to the offset of the gear plane and vertical plane. Taking gravity, tooth separation, backside contact and bedplate tilt angle into consideration, a rotational-translational-Axial Dynamic model of the spur planetary gear is developed. With two different load-sharing factor models, the load-sharing characteristics of the planetary gear in horizontal axis wind turbines are numerically investigated. The effects of gravity, ring support stiffness and bedplate tilt angle on load-sharing characteristics are systematically examined. When planets move to certain positions, severe unequal load-sharing and backside contact are more likely to happen. Load-sharing characteristics change with the bedplate tilt angle and the ring support stiffness, and the variation trend is closely related to the occurrence of tooth separation and backside contact.
Xinghui Qiu - One of the best experts on this subject based on the ideXlab platform.
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Dynamic modeling and analysis of the planetary gear under pitching base motion
International Journal of Mechanical Sciences, 2018Co-Authors: Xinghui Qiu, Qinkai Han, Fulei ChuAbstract:Abstract Planetary gear transmission is subjected to base motions in many industrial applications such as wind turbines and automobiles, and its Dynamic behavior will be affected by base motions. To develop a Dynamic model more suitable for the planetary gear under base motions, the general modeling procedures are illustrated in detail from the perspective of energy. A rotational-translational-Axial Dynamic model of the planetary gear under pitching base motion is proposed and validated. Pitching base motion causes additional damping, stiffness and forced excitation, which disrupts the force symmetry of the planetary gear and results in unequal load sharing. Dynamic responses of the planetary gear are obtained by numerical integration, and spectrum analysis is conducted using the Fourier transform. Spectra of the rotational and translational vibrations of the central components show completely different characteristics because of the structure symmetry of the planetary gear. The influences rules of parameters on response spectra and load sharing conditions are derived, including the amplitude and the frequency of the pitching base motion, and the carrier rotating speed. When the base excitation frequency approaches half the translational natural frequencies, the load sharing condition of the planetary gear will deteriorate rapidly. The load sharing factor increases by the square of the base excitation amplitude.
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load sharing characteristics of planetary gear transmission in horizontal axis wind turbines
Mechanism and Machine Theory, 2015Co-Authors: Xinghui Qiu, Fulei ChuAbstract:Abstract With the increase of wind turbine size, gravity becomes an important non-torque excitation source. Gravity disrupts the cyclic symmetry of the planetary gear and causes unequal load-sharing. Because of the specific operation conditions, the bedplate will tilt and lead to the offset of the gear plane and vertical plane. Taking gravity, tooth separation, backside contact and bedplate tilt angle into consideration, a rotational-translational-Axial Dynamic model of the spur planetary gear is developed. With two different load-sharing factor models, the load-sharing characteristics of the planetary gear in horizontal axis wind turbines are numerically investigated. The effects of gravity, ring support stiffness and bedplate tilt angle on load-sharing characteristics are systematically examined. When planets move to certain positions, severe unequal load-sharing and backside contact are more likely to happen. Load-sharing characteristics change with the bedplate tilt angle and the ring support stiffness, and the variation trend is closely related to the occurrence of tooth separation and backside contact.
Horacio D Espinosa - One of the best experts on this subject based on the ideXlab platform.
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MODELING OF CERAMIC MICROSTRUCTURES: Dynamic DAMAGE INITIATION AND EVOLUTION
2016Co-Authors: Edited M. D. Furnish, Horacio D Espinosa, L. C. Chhabildas, R. S. Hixson, Pablo D ZavattieriAbstract:A model is presented for the Dynamic finite element analysis of ceramic microstructures sub-jected to multi-Axial Dynamic loading. This model solves an initial-boundary value problem using a multi-body contact scheme integrated with interface elements to simulate microcracking at grain boundaries and subsequent large sliding, opening and closing of interfaces. A systematic and parametric study of the effect of interface element parameters, grain anisotropy, stochastic distribution of interface properties, grain size and grain morphology is carried out. Numerical results are shown in terms of microcrack patterns and evolution of crack density. The quali-tative and quantitative results presented in this article are useful in developing more refined continuum theories of fracture properties of ceramics
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a computational model of ceramic microstructures subjected to multi Axial Dynamic loading
Journal of The Mechanics and Physics of Solids, 2001Co-Authors: Pablo D Zavattieri, P V Raghuram, Horacio D EspinosaAbstract:A model is presented for the Dynamic finite element analysis of ceramic microstructures subjected to multi-Axial Dynamic loading. This model solves an initial-boundary value problem using a multi-body contact model integrated with interface elements to simulate microcracking at grain boundaries and subsequent large sliding, opening and closing of microcracks. An explicit time integration scheme is adopted to integrate the system of spatially discretized ordinary differential equations. A systematic and parametric study of the effect of interface element parameters, grain anisotropy, stochastic distribution of interface properties, grain size and grain morphology is carried out. Numerical results are shown in terms of microcrack patterns and evolution of crack density, i.e., damage kinetics. The brittle behavior of the microstructure as the interfacial strength decreases is investigated. Crack patterns on the representative volume element vary from grains totally detached from each other to a few short cracks, nucleated at voids, except, for the case of microstructures with initial flaws. Grain elastic anisotropy seems to play an important role in microfracture presenting higher values of crack density than the isotropic case. The computational results also show that decreasing the grain size results in a decrease in crack density per unit area at equal multiAxial Dynamic loading. Histograms of crack density distribution are presented for the study of the stochasticity of interface parameters. Finally, a strong dependency with grain shape is observed for different microstructures generated using Voronoi Tessellation. The micromechanical model here discussed allows the study of material pulverization upon unloading. The qualitative and quantitative results presented in this article are useful in developing more refined continuum theories on fracture properties of ceramics.
Patrick Mcgarry - One of the best experts on this subject based on the ideXlab platform.
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influence of multi Axial Dynamic constraint on cell alignment and contractility in engineered tissues
Journal of The Mechanical Behavior of Biomedical Materials, 2020Co-Authors: Noel H Reynolds, Eoin Mcevoy, Juan Alberto Panadero Perez, Ryan J Coleman, Patrick McgarryAbstract:Abstract In this study an experimental rig is developed to investigate the influence of tissue constraint and cyclic loading on cell alignment and active cell force generation in uniAxial and biAxial engineered tissues constructs. Addition of contractile cells to collagen hydrogels dramatically increases the measured forces in uniAxial and biAxial constructs under Dynamic loading. This increase in measured force is due to active cell contractility, as is evident from the decreased force after treatment with cytochalasin D. Prior to Dynamic loading, cells are highly aligned in uniAxially constrained tissues but are uniformly distributed in biAxially constrained tissues, demonstrating the importance of tissue constraints on cell alignment. Dynamic uniAxial stretching resulted in a slight increase in cell alignment in the centre of the tissue, whereas Dynamic biAxial stretching had no significant effect on cell alignment. Our active modelling framework accurately predicts our experimental trends and suggests that a slightly higher (3%) total SF formation occurs at the centre of a biAxial tissue compared to the uniAxial tissue. However, high alignment of SFs and lateral compaction in the case of the uniAxially constrained tissue results in a significantly higher (75%) actively generated cell contractile stress, compared to the biAxially constrained tissue. These findings have significant implications for engineering of contractile tissue constructs.
Fabrizio Scarpa - One of the best experts on this subject based on the ideXlab platform.
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numerical analysis of the impact resistance in aluminum alloy bi tubular thin walled structures designs inspired by beetle elytra
Journal of Materials Science, 2017Co-Authors: Jinwu Xiang, Fabrizio ScarpaAbstract:Thin-walled tubular structures are commonly used in automotive and aerospace applications because of their high strength and lightweight characteristics. In this paper we propose a new bionic bi-tubular thin-walled structure (BBTS) inspired from the internal structure of the lady beetle elytron. Six types of BBTSs with different geometric parameters and same type of material were simulated under Axial Dynamic impact loading with a weight of 500 kg and a velocity of 10 m/s using nonlinear finite elements. The comparison between BBTSs with equal mass shows that the thickness of the inner wall and the cross-sectional configurations influence significantly the energy absorption of the structure. BBTSs show an optimized crashworthiness behavior when the inner wall thickness is between 1.6 and 2.0 mm. In addition, circular and octangular BBTSs show improved absorption characteristics when the inner wall thickness is 2.0 mm. We also evaluate the energy absorption of periodically distributed BBTS against cellular configuration with irregular topology. The energy absorption characteristic of BBTS with regular distribution is better than that of BBTS with irregular distribution, which indicates that the optimized regular structure has an improved mechanical performance to the original bionic topology.
