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  • 1
    Online Resource
    Online Resource
    Incidence of active tuberculosis in individuals with latent tuberculosis infection in rural China: follow-up results of a population-based, multicentre, prospective cohort study
    Elsevier BV ; 2017
    In:  The Lancet Infectious Diseases Vol. 17, No. 10 ( 2017-10), p. 1053-1061
    Details
    In: The Lancet Infectious Diseases, Elsevier BV, Vol. 17, No. 10 ( 2017-10), p. 1053-1061
    Type of Medium: Online Resource
    ISSN: 1473-3099
    URL: Article
    DOI: 10.1016/S1473-3099(17)30402-4
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2017
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  • 2
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    Experimental and Theoretical Study of Gear Dynamical Transmission Characteristic Considering Measured Manufacturing Errors
    Hindawi Limited ; 2018
    In:  Shock and Vibration Vol. 2018 ( 2018-11-04), p. 1-20
    Details
    In: Shock and Vibration, Hindawi Limited, Vol. 2018 ( 2018-11-04), p. 1-20
    Abstract: In the research of gear transmission, the vibration and noise problem has received many concerns all the times. Scholars use tooth modification technique to improve the meshing state of gearings in order to reduce the vibration and noise. However, few of researchers consider the influence of measured manufacturing errors when they do the study of tooth modification. In order to investigate the efficiency of the tooth modification in the actual project, this paper proposes a dynamic model of a helical gear pair including tooth modification and measured manufacturing errors to do a deterministic analysis on the dynamical transmission performance. In this analysis, based on the measured tooth deviation, a real tooth surface (including modification and measured tooth profile error) is fitted by a bicubic B-spline. With the tooth contact analysis (TCA) and loaded tooth contact analysis (LTCA) on the real tooth surface, the loaded transmission error, tooth surface elastic deformation, and load distribution can be determined. Based on the results, the time-varying mesh stiffness and gear mesh impact are computed. Taking the loaded transmission error, measured cumulative pitch error, eccentricity error, time-varying mesh stiffness, and gear mesh impact as the internal excitations, this paper establishes a 12-degree-of-freedom (DOF) dynamic model of a helical gear pair and uses the Fourier series method to solve it. In two situations of low speed and high speed, the gear system dynamic response is analyzed in the time and frequency domains. In addition, an experiment is performed to validate the simulation results. The study shows that the proposed technique is useful and reliable for predicting the dynamic response of a gear system.
    Type of Medium: Online Resource
    ISSN: 1070-9622 , 1875-9203
    URL: Article
    DOI: 10.1155/2018/9645453
    Language: English
    Publisher: Hindawi Limited
    Publication Date: 2018
    detail.hit.zdb_id: 2070162-7
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  • 3
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    Online Resource
    Influence of the Eccentric Error of Star Gear on the Bifurcation Properties of Herringbone Star Gear Transmission with Floating Sun Gear
    Hindawi Limited ; 2018
    In:  Shock and Vibration Vol. 2018 ( 2018), p. 1-32
    Details
    In: Shock and Vibration, Hindawi Limited, Vol. 2018 ( 2018), p. 1-32
    Abstract: Taking a herringbone star gear transmission (HSGT) with floating sun gear as an example, the system bifurcation characteristics with the changing of the eccentric error of star gear and the working frequencies are analyzed. For this analysis, a generalized dynamic model of HSGT considering the manufacturing eccentric errors, time-varying mesh stiffness, and load balancing mechanism is established and solved by numerical method. The floating process of sun gear is explained. In this paper, there are seven cases about the eccentric errors of star gears which are calculated, respectively. To study the effect of the working frequencies (including meshing frequency and rotation frequency), the calculation is done at three kinds of input speed in which the working frequencies are close to the system natural frequencies. The results are demonstrated in detail by the bifurcation diagrams, phase plane plots, and Poincare maps. The system bifurcation characteristics are particularly analyzed and compared in every case. This work provides important guidance to the engineering of HSGT.
    Type of Medium: Online Resource
    ISSN: 1070-9622 , 1875-9203
    URL: Article
    DOI: 10.1155/2018/6014570
    Language: English
    Publisher: Hindawi Limited
    Publication Date: 2018
    detail.hit.zdb_id: 2070162-7
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  • 4
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    Online Resource
    The statistical analysis of the dynamic performance of a gear system considering random manufacturing errors under different levels of machining precision
    SAGE Publications ; 2020
    In:  Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics Vol. 234, No. 1 ( 2020-03), p. 3-18
    Details
    In: Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics, SAGE Publications, Vol. 234, No. 1 ( 2020-03), p. 3-18
    Abstract: Gear manufacturing error is one of the main sources of vibration and noise in gears; its influence on the dynamic transmission behaviour of gear systems is a research hotspot. In the current study on the effect of the manufacturing errors, the processing methods of the errors are mostly rough or hypothetical, so the analysis results cannot provide high reference value. This paper proposes a distinctive method to analyse the vibration response of helical gears in the presence of random manufacturing errors and modifications. The presented study performs tooth contact analysis (TCA) with the real tooth surface containing the random tooth profile error and the modification and performs loaded tooth contact analysis (LTCA) based on the superposition of the random pitch error and the initial gap between mating teeth obtained by TCA. Furthermore, the dynamic excitations, including time-varying mesh stiffness and meshing impact, are computed using the above-mentioned TCA and LTCA. The processing method for the manufacturing errors in this paper is reasonable and close to the actual situation of gear engagement. Using this proposed method, statistical analysis was carried out under machining accuracy grades 5, 6 and 7 to show the effect of the different distributions of random manufacturing errors on the gear vibration. The analysis results are of practical significance and provide references for the design and vibration control of gear drive systems.
    Type of Medium: Online Resource
    ISSN: 1464-4193 , 2041-3068
    URL: Article
    DOI: 10.1177/1464419319862165
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2020
    detail.hit.zdb_id: 2032771-7
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  • 5
    Online Resource
    Online Resource
    An effective modelling approach for multi-body dynamic analysis of epicyclic gear train of GTF considering both structural flexibility and mechanical interactions
    SAGE Publications ; 2023
    In:  Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics
    Details
    In: Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics, SAGE Publications
    Abstract: In this paper, a new modelling approach is proposed for the dynamic investigation of epicyclic gear train, and the novelty of this work lies in consideration of both structural flexibility and mechanical interactions during the analysis procedure. The method is of capacity to directly present the dynamic results of the supporting structure for convenient practical engineering evaluation and reduce the dimension of the system reasonably with appropriate assumptions for better computational efficiency. Firstly, the mechanical interactions among components are discussed in detail, and the principle that the structural flexibility works is also explained at length. Secondly, taking the epicyclic gear train of the geared turbofan (GTF) engine; for example, the dynamic model of the system is then established based on the developed hybrid user-defined elements. For model validation, the governing equations of the system are also derived by the lumped mass method. Thirdly, with the same values of the parameters, the results of normal dynamic meshing force obtained by the proposed model are compared with the ones by the lumped mass model. It can be stated from the data that (1) the maximum relative error between the theoretical value and the average value calculated by the two models is 8.28%, (2) the gear mesh frequency obtained by the two models are sufficiently close to the theoretical value, and (3) the fluctuation trends of the dynamic force keep basically consistent with each other. In summary, the comparison presented clearly indicates that the proposed model is indeed reasonable, which provides a new way for dynamic investigation and structural redesign of a large epicyclic gear train. Finally, as a practical engineering application, the vibration result of the deformable supporting structure of the GTF gear train is also presented, which directly provides valuable reference for vibration monitoring, fault diagnosis and other engineering problems in practice.
    Type of Medium: Online Resource
    ISSN: 1464-4193 , 2041-3068
    URL: Article
    DOI: 10.1177/14644193231203592
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
    detail.hit.zdb_id: 2032771-7
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  • 6
    Online Resource
    Online Resource
    Dynamic analysis of a helical gear reduction by experimental and numerical methods
    Institute of Noise Control Engineering (INCE) ; 2020
    In:  Noise Control Engineering Journal Vol. 68, No. 1 ( 2020-01-20), p. 48-58
    Details
    In: Noise Control Engineering Journal, Institute of Noise Control Engineering (INCE), Vol. 68, No. 1 ( 2020-01-20), p. 48-58
    Abstract: Presented in this study is investigation of dynamic behavior of a helical gear reduction by experimental and numerical methods. A closed-loop test rig is designed to measure vibrations of the example system, and the basic principle as well as relevant signal processing method is introduced. A hybrid user-defined element model is established to predict relative vibration acceleration at the gear mesh in a direction normal to contact surfaces. The other two numerical models are also constructed by lumped mass method and contact FEM to compare with the previous model in terms of dynamic responses of the system. First, the experiment data demonstrate that the loaded transmission error calculated by LTCA method is generally acceptable and that the assumption ignoring the tooth backlash is valid under the conditions of large loads. Second, under the common operating conditions, the system vibrations obtained by the experimental and numerical methods primarily occur at the first fourth-order meshing frequencies and that the maximum vibration amplitude, for each method, appears on the fourth-order meshing frequency. Moreover, root-mean-square (RMS) value of the acceleration increases with the increasing loads. Finally, according to the comparison of the simulation results, the variation tendencies of the RMS value along with input rotational speed agree well and that the frequencies where the resonances occur keep coincident generally. With summaries of merit and demerit, application of each numerical method is suggested for dynamic analysis of cylindrical gear system, which aids designers for desirable dynamic behavior of the system and better solutions to engineering problems.
    Type of Medium: Online Resource
    ISSN: 0736-2501
    URL: Article
    DOI: 10.3397/1/37684
    Language: English
    Publisher: Institute of Noise Control Engineering (INCE)
    Publication Date: 2020
    detail.hit.zdb_id: 2631757-6
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  • 7
    Online Resource
    Online Resource
    Static contact analysis of spiral bevel gear based on modified VFIFE (vector form intrinsic finite element) method
    Elsevier BV ; 2018
    In:  Applied Mathematical Modelling Vol. 60 ( 2018-08), p. 192-207
    Details
    In: Applied Mathematical Modelling, Elsevier BV, Vol. 60 ( 2018-08), p. 192-207
    Type of Medium: Online Resource
    ISSN: 0307-904X
    URL: Article
    DOI: 10.1016/j.apm.2018.03.021
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2018
    detail.hit.zdb_id: 2004151-2
    detail.hit.zdb_id: 197129-3
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  • 8
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    Online Resource
    Computerized generation and simulation of meshing of a novel crown gear coupling avoiding edge contact
    Japan Society of Mechanical Engineers ; 2019
    In:  Journal of Advanced Mechanical Design, Systems, and Manufacturing Vol. 13, No. 3 ( 2019), p. JAMDSM0055-JAMDSM0055
    Details
    In: Journal of Advanced Mechanical Design, Systems, and Manufacturing, Japan Society of Mechanical Engineers, Vol. 13, No. 3 ( 2019), p. JAMDSM0055-JAMDSM0055
    Type of Medium: Online Resource
    ISSN: 1881-3054
    URL: Article
    DOI: 10.1299/jamdsm.2019jamdsm0055
    Language: English
    Publisher: Japan Society of Mechanical Engineers
    Publication Date: 2019
    detail.hit.zdb_id: 2395570-3
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  • 9
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    Online Resource
    Design and analysis of herringbone gear with sixth-order transmission error based on meshing vibration optimization
    SAGE Publications ; 2017
    In:  Advances in Mechanical Engineering Vol. 9, No. 6 ( 2017-06), p. 168781401770435-
    Details
    In: Advances in Mechanical Engineering, SAGE Publications, Vol. 9, No. 6 ( 2017-06), p. 168781401770435-
    Type of Medium: Online Resource
    ISSN: 1687-8140 , 1687-8140
    URL: Article
    DOI: 10.1177/1687814017704359
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2017
    detail.hit.zdb_id: 2501620-9
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  • 10
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    Online Resource
    Investigation of Load Sharing and Dynamic Load Characteristics of a Split Torque Transmission System with Double-Helical Gear Modification
    Hindawi Limited ; 2021
    In:  Shock and Vibration Vol. 2021 ( 2021-6-29), p. 1-22
    Details
    In: Shock and Vibration, Hindawi Limited, Vol. 2021 ( 2021-6-29), p. 1-22
    Abstract: A new dynamic model for a two-input two-path split torque transmission system which considers meshing error, time-varying meshing stiffness, and meshing-in impact is proposed. Time-varying meshing stiffness and meshing-in impact of each gear pair are accurately calculated based on tooth contact analysis and loaded tooth contact analysis. Equivalent displacements of eccentricity error and installation error along the meshing line of second- and third-stages gears are derived. The modified tooth surface of a third-stage double-helical gear is obtained by optimizing the amplitude of static loaded transmission error and meshing-in impact via nondominated sorting genetic algorithm-II (NSGA-II). Influence of modification on load sharing and dynamic load characteristics of split torque transmission system is investigated. The results indicate that the system’s dynamic meshing force increases when meshing-in impact is accounted for, which is unfavorable for the transmission. Following the modification of a double-helical gear, the dynamic load characteristics of the split torque transmission system are significantly improved, while its load sharing characteristics are improved to a certain extent.
    Type of Medium: Online Resource
    ISSN: 1875-9203 , 1070-9622
    URL: Article
    DOI: 10.1155/2021/9912148
    Language: English
    Publisher: Hindawi Limited
    Publication Date: 2021
    detail.hit.zdb_id: 2070162-7
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