Papers by Keyword: Gyroscopic Effect

Abstract: This article is presents a finite element formulation for the dynamic response of a rotating simply supported shaft subjected to a moving load. The Timoshenko beam theory is used to model the rotating shaft. The assumed modes method and Finite Element method are employed in this study. The equations are solved with numerical method. The influence of parameters moving load speed and rotational speed are discussed for rotating simply supported shaft model. The results show that the maximum displacement occurs in the direction of the load at the midpoint of the simply supported shaft. The gyroscopic effect occurs only in the direction perpendicular to the load and is dependent on rotational speed of the shaft.

Abstract: The flywheel energy storage technology is a new type of conversion and storage for electric energy, and it is also a research hotspot of energy field in the world. There are a large number of studies on dynamic characteristics of energy storage flywheel in recent years. The flexible support with a single point has small load-carrying ability but very low friction loss, which is appropriate to be used in small flywheel system. By using a small stiffness pivot-jewel bearing and an oil damper as the lower support of the flywheel, a high-speed flywheel shafting with a single point flexible support was built. The dynamic model of the shafting was obtained by means of the Lagrangian equation. Based on the same energy dissipation of oil damper and flywheel, the optimal equivalent damping of flywheel was determined. The optimization criteria for dynamic state and parameters between oil damper and shafting were also presented. The lower damper’s effects on the mode shapes, modal damping ratios and forced vibration were discussed.

Abstract: The aft part of large scale vessel propulsion shaft is a cantilever with a propeller. As the shaft doing the lateral vibration, the trail of propeller shaft center-line, which appears together with the movement, is the cone surface with the shaft center as the symmetrical axis, at the same time the propeller will vibrate with the shaft. In order to investigate the influence of propeller effect to shaft lateral vibration, the main work in the paper includes modeling the finite element of a large scale vessel propulsion shaft, studying the factors of water mass adhered to propeller, pin softening and gyroscopic moment to the shaft lateral vibration. The calculation shows that: if the propeller's gyroscopic moment is positive, the free frequency of shaft will increase, while added water mass and spin softening will obviously decrease the free vibration frequency of shaft.

Abstract: High-speed milling (HSM) has advantages in high productivity high precision and low production cost. Thus it can be widely used in the manufacture industry. However, when the speed of spindle-tool reaches a higher speed range, the gyroscopic effect will become an important part of its stable milling. In this paper, a dynamics model of HSM system was proposed considering the influence of gyroscopic moment due to high rotating speed of end milling. Finite element model (FEM) is used to model the dynamics of a spindle-milling system. It obtains the trajectory of central point in face milling with considering gyroscopic effects through the dynamics model at high speeds. Then the cutting force model will be corrected by the trajectory of face milling. Then the stability lobes diagrams (SLD) was elaborated. Cutting thickness effects have non-negligible impact on stability limitation.

Abstract: Gyroscopic effects in the flywheel rotor greatly influence rotor stability especially at high speed. When the pole-zero position moves to right of s-plane, the damping of the pole is getting smaller, and the stability of system is getting worse with the increasing of rotor speed when the decentralized PD control law is used only. The LQR (linear quadratic regulator) control method is used to reduce gyroscopic effect and forced vibration. The simulation results show that LQR controller have a good performance on the reduction of gyroscopic effect and vibration of magnetic flywheel rotor system.

Abstract: High-speed milling (HSM) has advantages in high productivity high precision and low production cost. Thus it can be widely used in the manufacture industry. However, when the speed of spindle-tool reaches a higher speed range, the gyroscopic effect will become an important part of its stable milling. In this paper, a dynamics model of HSM system was proposed considering the influence of gyroscopic moment due to high rotating speed of end milling, and solution it. Then, the natural frequencies of end-milling model were researched by using analyse software. And analysis the stability of end-milling that considered gyroscopic effects under different speeds, obtain the Campbell Diagram. Get the trajectory of one point in end face milling. Then draw the fitting trajectory and ideal trajectory of the point in milling. Compare the actual trajectory, fitting trajectory and the ideal trajectory. So it can provide a basis for stability prediction of high speed milling.

Abstract: Although the gyroscopic effect on rotor system has been noticed for decades, it is often underestimated and even ignored in the simplified model; moreover the comparing analyses of it on dynamics of rotor system with distributed masses are rarely performed. In this paper, a model of dual-disk rotor system with 8 degree-of-freedoms is developed to show the gyroscopic effects, especially on asymmetric rotor system, in which the polar and transversal moments of inertia of the disks are incorporated. The critical speeds and unbalance responses of such a rotor system are simulated numerically and compared respectively in 4 different asymmetric cases, including 2 cases of position asymmetry and another 2 cases of support stiffness asymmetry. The analysis results clearly show that the gyroscopic effect has obvious influence on the critical speeds and unbalance responses under different asymmetry conditions.

Abstract: The efficiency of the high-speed milling process is often limited by the occurrence of chatter. In order to predict the occurrence of chatter, accurate models are necessary. With the speed increasing, gyroscopic effect plays an important pole on the system behavior, including dynamic characteristic and rotating behavior. Considering the influence of gyroscopic effect on rotating behavior, an updated model for the milling process is presented which features as model of the equivalent profile of tool. In combination with this model, a nonlinear instantaneous cutting force model is proposed. The use of this updated equivalent profile of tool results in significant differences in the static uncut thickness compared to the traditional model.

Abstract: In the high-speed, gyroscopic effects of the flywheel rotor greatly influence the rotor stability. The pole-zero points move to right of s-plane and the damping terms of the pole points become smaller. The stability of the system will get worse with the increasing of rotor speed when the traditional decentralized PD controller is used only. In the paper, a cross-feedback control with decentralized PD control is used for compensating gyroscopic effect. The simulation results show that the system stability is better using the cross-feedback control with decentralized PD control than using the traditional decentralized PD control.

Abstract: High-speed milling (HSM) has advantages in high productivity high precision and low production cost. Thus it can be widely used in the manufacture industry. However, when the speed of spindle-tool reaches a higher speed range, the gyroscopic effect will become an important part of its stable milling. In this paper, a dynamics model of HSM system was proposed considering the influence of gyroscopic moment due to high rotating speed of end milling. Finite element model (FEM) is used to model the dynamics of a spindle-milling system. It obtains the trajectory of central point in face milling with considering gyroscopic effects through the dynamics model at high speeds. Then the cutting force model will be corrected by the trajectory of face milling. So it can provide a basis for stability prediction of high speed milling.