Dynamic analysis of a helical geared rotor-bearing system with composite rotating shafts

Purpose This study aims to study the dynamic characteristics of a helical geared rotor-bearing system with composite material rotating shafts. Design/methodology/approach A finite element model of a helical geared rotor-bearing system with composite material rotating shafts is developed, in which the rotating shafts of the system are composed of composite material and modeled as Timoshenko beam; a rigid mass is used to represent the gear and their gyroscopic effect is taken into account; bearings are modeled as linear spring-damper; and the equations of motion are obtained by applying Lagrange’s equation. Natural frequencies, mode description, lateral responses, axial responses, lamination angles, lamination numbers, gear mesh stiffness and bearing damping coefficients are investigated. Findings The desired mechanical properties could be constructed using different lamination numbers and fiber included angles by composite rotating shafts. The frequency of the lateral module decreases as the included angle of the fibers and the principal shaft of the composite material rotating shaft increase. Because of the gear mesh stiffness increase, the resonance frequency of the coupling module of the system decreases, the lateral module is not influenced and the steady-state response decreases. The amplitude of the steady-state lateral and axial responses gradually decreases as the bearing damping coefficient increases. Practical implications The model of a helical geared rotor-bearing system with composite material rotating shafts is established in this paper. The dynamic characteristics of a helical geared rotor-bearing system with composite rotating shafts are investigated. The numerical results of this study can be used as a reference for subsequent personnel research. Originality/value The dynamic characteristics of the geared rotor-bearing system had been reported in some literature. However, the dynamic analysis of a helical geared rotor-bearing system with composite material rotating shafts is still rarely investigated. This paper shows some novel results of lateral and axial response results obtained by different lamination angles and different lamination numbers. In the future, it makes valuable contributions for further development of dynamic analysis of a helical geared rotor-bearing system with composite material rotating shafts.

Bifurcation Analysis of Gear Pair with Continuous and Intermittent Mesh Stiffness Using Enhanced Compliance Method

The nonlinear dynamics of a multigear pair with the time-varying gear mesh stiffness are investigated using an enhanced compliance-based methodology. In the proposed approach, Lagrangian theory and Runge–Kutta method are used to derive the equation of motion of the multigear pair and solve its dynamic response for various values of the gear mesh frequency, respectively. The simulation results obtained for the dynamic behavior of the multigear pair are compared with those obtained by using continuous (cosine, sine and offset sine function) and intermittent representations of the time-varying gear mesh stiffness. It is shown that periodic, quasi-periodic, aperiodic and chaos motions are induced at different values of the gear mesh frequency. In addition, the bifurcation diagram reveals the occurrence of both nonimpact motion and single-sided impact motion, and Lyapunov exponent can easily diagnose the chaos phenomenon of system.

An Analytical Investigation of Rattle Characteristics of Powder Metal Gears

This study employs an analytical model of a gear pair with transverse-torsional dynamics that allows analysis of single-sided, double-sided, and random rattle situations to contrast rattle characteristics of isotropic PM gears with a baseline steel gearset. This model utilizes time-varying gear mesh stiffness and transmission error as the internal excitation sources and time-varying operating torque as an external excitation. The gear rattle performance of PM gears is investigated under different torque conditions and operating speeds. The system kinetic and potential energy is assessed as an evaluation tool that can indicate the severity of different rattle conditions. The dynamic response of two different versions of an existing PM gear design are compared with a baseline traditional steel gear.

Load sharing characteristic of a power-integrated gearbox in a hydraulic top-drive system

With the increase in drilling depth, a slight conical pendulum movement of drilling strings causes the external drilling load becoming a non-negligible excitation source. The phenomenon of unique load sharing would be generated by irregular external load, which has complex influence on cyclic and axial symmetry of a power integrated gearbox. Bearing wear, which brings high frequency unpredictable vibration into the transmission system, is likely to occur because of the specific drive mode of the hydraulic top-drive system applied in well drilling. A systematic model combining the finite element method and the multi-body dynamics of a power-integrated gearbox simulation system is developed in this study with the characteristics of the power system, external load, driving forces, gear mesh stiffness, and bearing support stiffness taken into consideration. The load sharing characteristics of the power-integrated gearbox in a hydraulic top-drive system are numerically investigated. Moreover, the effects of gear mesh stiffness, bearing support stiffness, lateral load, and bearing clearance on the load sharing characteristics are systematically examined. Analysis results show that the dynamic process must be considered to achieve a comprehensive evaluation of the load sharing characteristics of a power-integrated gearbox. Evaluation results indicate that lateral load is the factor that influence the load sharing factor of the power-integrated gearbox most significantly, based on which, predictions can be safely made so that some additional mechanisms might be a practical option to diminish that effect.