Nonlinear torsional instabilities in two-stage gear systems with flexible shafts

Chen

Proceedings of the Institution of Mechanical Engineers, Part C:

et al. 2021

The coupled dynamic model of the intermediate and tail gearboxes’ spiral bevel gear-oblique tail shaft-laminated membrane coupling was established by employing the hybrid modeling method of finite element and lumped mass. Among them, the dynamic equation of the shaft was constructed by Timoshenko beam; spiral bevel gears were derived theoretically by the lumped-mass method, where the effects of time-varying meshing stiffness, transmission error, external imbalance excitation and the like were considered simultaneously; laminated membrane coupling was simplified to a lumped parameter model, in which the stiffness was obtained by the finite element simulation and experiment. On this basis, the laminated membrane coupling and effects of several important parameters, including the unbalance value, tail rotor excitation, oblique tail shaft’s length and transmission error amplitude, on the system’s dynamic characteristics were discussed. The results showed that the influences of laminated membrane coupling and transmission error amplitude on the coupled system’s vibration response were prominent, which should be taken into consideration in the dynamic model. Due to the bending-torsional coupled effect, the lateral vibration caused by gear eccentricity would enlarge the oblique tail shaft’s torsional vibration; similarly, the tail rotor’s torsional excitation also varies the lateral vibration of the oblique tail shaft. The coupled effect between the eccentricity of gear pairs mainly hit the torsional vibration. Also, as the oblique tail shaft’s length increased, the torsional vibration of the oblique tail shaft tended to diminish while the axis orbit became larger. The research provides theoretical support for the design of the helicopter tail transmission system.

Section: Introductionmentioning

confidence: 99%

Modeling and dynamic analysis of spiral bevel gear coupled system of intermediate and tail gearboxes in a helicopter

Chen

Proceedings of the Institution of Mechanical Engineers, Part C:

et al. 2021

“…Their knowledge enables the avoidance of operating the system in resonance zones, which affects the durability and proper operation of the device. The system parameters can be selected, regarding the dynamic properties, by using the optimization algorithms [5][6][7], modeling [19][20][21][22], or synthesis [9][10][11][12][13][14][15][16][17][18], due to an introduction of simulation tests with the use of computers. Simulation tests, belonging to the scope of theoretical tests, allow us to analyze the impact of the selected parameters on mechanical characteristics.…”

Section: Introductionmentioning

confidence: 99%

“…To obtain real parameters of the synthesized gear, the gear ratio, Equation (21), should be taken into account. This is done by multiplying the obtained parameters of the drive system, with the gear ratio selected on each stage (this applies to the case where the system is reduced to a drive member), in the form of: mass moments of inertia:…”

mentioning

confidence: 99%

Designing of Drive Systems in the Aspect of the Desired Spectrum of Operation

et al. 2021

A method for selecting dynamic parameters and structures of drive systems using the synthesis algorithm is presented. The dynamic parameters of the system with six degrees of freedom, consisting of a power component (motor) and a two-speed gearbox, were determined, based on a formalized methodology. The required gearbox is to work in specific resonance zones, i.e., meet the required dynamic properties such as the required resonance frequencies. In the result of the tests, a series of parameters of the drive system, defining the required dynamic properties such as the resonance and anti-resonance frequencies were recorded. Mass moments of inertia of the wheels and elastic components, contained in the required structure of the driving system, were determined for the selected parameters obtained during the synthesis.

“…Regarding the oil squeezing between teeth, the effects of periodic backlash on gear vibration were analyzed by Ernesto Rocca et al [16]. Z. Rao et al [17] studied the nonlinear torsional instability of a two-stage gear system with a flexible shaft. Karahman et al [18] analyzed the coupling between time-varying stiffness, backlash and the bearing gap based on the nonlinear time-varying model.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear dynamic response analysis of two-stage spur gear space driving mechanism with large inertia load

Ma¹,

Li²,

Luo³

et al. 2018

J. vibroeng.

Large inertia load has been widely used in space driving mechanisms, but the research concerning theory is still an unexplored scientific field. Towards the problem of nonlinear disturbance in space driving mechanism with large inertia load, a 14-DOF (Degree of Freedom) nonlinear, time-varying, dynamic model of two-stage spur gear system was established, taking into consideration time-varying stiffness, backlash and transmission error. The dynamic response of the load, under large or small inertia was investigated, basing on the dynamic model. The results indicate that at starting, normal operation and braking, large inertia load system has obvious hysteresis, compared to small inertia. The factors that improve dynamic response speed under large inertia load were studied. The results indicate that improving the stiffness and damping of the output shaft and changing the material of second gear pair to titanium alloy are helpful in improving the dynamic response speed of the system. Some results enrich the research of two-stage spur gear nonlinear model and large inertia load, since they provide important reference for the actual design of the gear system.