Critical speed

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

Influence of Rotation on Vibration Behavior of a Functionally Graded Moderately Thick Cylindrical Nanoshell Considering Initial Hoop Tension

Abstract: In this research, the effect of rotation on the free vibration is investigated for the size-dependent cylindrical functionally graded (FG) nanoshell by means of the modified couple stress theory (MCST). MCST is applied to make the design and the analysis of nano actuators and nano sensors more reliable. Here the equations of motion and boundary conditions are derived using minimum potential energy principle and first-order shear deformation theory (FSDT). The formulation consists of the Coriolis, centrifugal and initial hoop tension effects due to the rotation. The accuracy of the presented model is verified with literatures. The novelty of this study is the consideration of the rotation effects along with the satisfaction of various boundary conditions. Generalized differential quadrature method (GDQM) is employed to discretize the equations of motion. Then the investigation has been made into the influence of some factors such as the material length scale parameter, angular velocity, length to radius ratio, FG power index and boundary conditions on the critical speed and natural frequency of the rotating cylindrical FG nanoshell.

Development of a simulation model of a high-speed vehicle for a derailment mechanism:

Abstract: During the operation of a high speed railway vehicle, safety is a basic requirement. However, due to the potentially large lateral displacements of the wheelsets, the precise mechanism of derailment is different from conventional vehicles and is not fully understood. To obtain correct simulation results for this behavior it is necessary to select methods for rapid, exact computation of the creep forces, the normal force, and the 3-D geometry at each contact point. In this paper, a dynamic model is presented and 2 types of derailment have been thoroughly investigated. High lateral force is used as a criterion for determining the critical point at which flange climb occurs and the critical speed for impact derailment is derived using the oblique-impact theory. Finally, an assessment method is proposed that distinguishes between the 2 types of derailment. The simulation model can also be used to identify the factors that lead to greatest risk of derailment.

Flutter of a viscoelastic plate in a supersonic gas flow

Abstract: The flutter of a viscoelastic plate in a supersonic gas flow is studied. A technique and algorithm for numerical solution of nonlinear integro-differential equations with weakly singular kernels are elaborated. The critical flutter speed of viscoelastic plates is determined

Computational Techniques of Rotor Dynamics with the Finite Element Method

Abstract: Part I: Theoretical Foundation of Rotor Dynamics Introduction to Rotational Physics Fixed Coordinate System Rotating Coordinate System Forces in the Rotating System Transformation between Coordinate Systems Kinetic Energy Due to Translational Displacement Kinetic Energy Due to Rotational Displacement Equation of Motion in Rotating Coordinate System Equation of Motion in the Fixed Coordinate System Coupled Solution Formulations Matrix Formulation of Lagrange's Equations Coupling Nodal Translations to the Stationary Part Simultaneous Coupling of Translations and Rotations Full Coupling of the Stationary and Rotating Parts Time-Dependent Terms of Equations Finite Element Analysis of Rotating Structures Potential Energy of Structure Dissipative Forces Non-dissipative Forces Finite Element Equation Assembly Coupled Equilibrium Equation Assembly Analysis Equilibrium Equations Computational Solution Techniques Direct Time Domain Solution of the Equilibrium Equation Direct Frequency Domain Solution Direct Free Vibration Solution Modal Solution Technique Static Condensation Dynamic Reduction Numerical Solution Techniques The Lanczos Method Orthogonal Factorization The Block Lanczos Method Solution of Periodic Equations Part II: Engineering Analysis of Rotating Structures Resonances and Instabilities Analysis Type vs. Modeling Approach Resonances and Instabilities Critical Speed of Rotating Mass The Laval Rotor Influence of Damping Unsymmetric Effects of Bearing and Rotor A Rotating Tube Rotating Model with Flexible Arms The Ground Resonance Dynamic Response Analysis Frequency Response without Rotation Frequency Response with Rotation Transient Response without Rotation Transient Response with Rotation A Finite Element Case Study Turbine Wheel with Shaft and Blades Engineering Analysis Computational Statistics The Journal Bearing Active External Loads Analysis of Aircraft Propellers A Propeller Blade Quasi-steady Aerodynamics of Blade Unsteady Aerodynamics of Blade Propeller with Four Blades Analysis of Wind Turbines An Example Wind Turbine Modeling and Analysis of Wind Turbine Blade Wind Turbine with Three Blades Response Analysis of Wind Turbines Horizontal Axis Wind Turbines with Two Blades