Critical speed

About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.

Dynamic Behavior of Cracked Flexible Rotor Subjected to Constant Driving Torque

Abstract: The dynamic behavior of a cracked flexible rotor passing through critical speed under the presence of a constant driving torque is analyzed. By incorporating the nonlinear coupling between the bending and torsional degrees of freedom , the model more accurately describes the behavior of the accelerated cracked rotor, especially near the resonance. The breathing types of cracks are considered using simple hinge model for small cracks and cosine function for deep ones. The applied strategy enables to study the cracked rotor dynamic response with and without weight dominance, taking into account also nonsynchronous whirl. The local cross- flexibility for deep cracks is taken into account. The effect of crack on “stalling” of the rotor is investigated. Under the constant driving torque, the vibration amplitude increases and the stalling angular velocity decreases with the depth of the crack.

Vibration analysis of functionally graded nanocomposite plate moving in two directions

Abstract: In the present study, vibration analysis of functionally graded carbon nanotube reinforced composite (FGCNTRC) plate moving in two directions is investigated. Various types of shear deformation theories are utilized to obtain more accurate and simplest theory. Single-walled carbon nanotubes (SWCNTs) are selected as a reinforcement of composite face sheets inside Poly methyl methacrylate (PMMA) matrix. Moreover, different kinds of distributions of CNTs are considered. Based on extended rule of mixture, the structural properties of composite face sheets are considered. Motion equations are obtained by Hamilton's principle and solved analytically. Influences of various parameters such as moving speed in x and y directions, volume fraction and distribution of CNTs, orthotropic viscoelastic surrounding medium, thickness and aspect ratio of composite plate on the vibration characteristics of moving system are discussed in details. The results indicated that thenatural frequency or stability of FGCNTRC plate is strongly dependent on axially moving speed. Moreover, a better configuration of the nanotube embedded in plate can be used to increase the critical speed, as a result, the stability is improved. The results of this investigation can be used in design and manufacturing of marine vessels and aircrafts.

Stabilization control for the hunting motion of a railway wheelset

Abstract: Rail vehicles experience the problem of hunting above a certain speed. The phenomenon is a kind of self-excited oscillation due to the unsymmetrical stiffness matrix in the equation of motion. In the present paper, a stabilization control method is proposed for the hunting motion in a wheelset model with two degrees of freedom by reducing the unsymmetrical effect of the stiffness matrix. It is theoretically shown under this control that the critical speed is infinite and no hunting motion occurs at any finite forward speed. Furthermore, an experimental study is conducted using a simple model and the validity of the control method is experimentally discussed. For the covering abstract see ITRD E111409.