This paper deals with the basic dynamical model of electromotor whose creation motivated by problems of electromotor vibrations and its subsequent fatigue. The model is chaacrterized by a flexible shaft with mounted padket of sheet metals that are equipped with parallel copper bars connected by end shortcircuit rings. Finite element analysis is used for the disretization of the shaft, while the sheet metal packet of cylindrical shape is modelled as a set of rigid bodies joined using chosen viscoelastic forces and torques. The shortcircuit rings are supposed to be rigid in this basic dynamical model and the pieces of copper bars are substituted by massless springs of calculated properties. Problematic model parameters are identified by means of performed experimental modal analysis. and Obsahuje seznam literatury
Fibres, cables, wires and fibres can play an important role in design of many machines. One of the most interesting applications is replacement of chosen rigid elements of a manipulator or a mechanism by cables. The main advantage of this design is the achievement of a lower moving inertia, which leads to a higher mechanism speed, and lower production costs. An inverted pendulum attached and driven by two fibres serves as a typical testing system for the investigation of the fibres properties influence of the system dynamic response. Motion of the pendulum of this nonlinear system is investigated using the alaska simulation tool and an in-house program created in the MATLAB system. Since mass of fibres can influence employed types of fibre models, chosen dynamic quantities (e.g. pendulum angle, vibration amplitude etc.), are investigated in dependence on the excitation frequency for various fibres weights. and Obsahuje seznam literatury
Experimental measurement is performed on a simple fibre-mass system: a moving mass coupled with the frame by a fibre. Dynamic response of the mass is measured. The same system is numerically investigated by means of a simple multibody model. The influence of the model parameters on the coincidence of results of experimental measurements and of simulations are evaluated. The simulations aim is to create a phenomenological model of a fibre, which will be utilizable in fibre modelling in the case of more complicated mechanical or mechatronic systems. and Obsahuje seznam literatury
This paper focuses on the modelling of harmonic vibration of two rotating blades affected by friction in contact of a rigid body placed in between the blade shroud. Harmonic blade excitation uniformly distributed in blade nodes in circumferential and axial direction is supposed. Flexible blades are discretized by FEM using 1D Rayleigh beam elements. The nonlinear friction forces in contact surfaces between the blade shroud and the friction element are taken into account using the harmonic balance method. Orbits of central contact points and dissipation energy are investigated in dependence on the excitation frequency. Dissipation energy amount in contact surfaces is confronted with blade tips vibration. and Obsahuje seznam literatury
Gearboxes and similar machines containing rotating parts are complex systems with complicated structure and couplings. Generally they can be decomposed into more simple subsystems. These subsystems are usually rotating shafts with gears joined
by gear couplings and housing coupled with rotating shafts by bearings. The paper is aimed at the mathematical modelling of gearboxes with spur helical gears considered including their interior rotating shaft system and housing. The used bearing model
respects real number of rolling elements and roller contact forces acting between the journals and the outer housing. The model of a complete gearbox is created using the modal synthesis method. The kinematic transmission errors in gear couplings are viewed as sources of excitation. Vibration and noise analysis of the gearbox housing is performed by means of the created model. Four types of objective functions suitable for optimization from the radiated noise point of view are proposed. The presented methodology is applied to the simple test-gearbox. and Obsahuje seznam literatury
The aim of the paper is to show the influence of design parameters on the suppression of rotating blade vibration. The derivation of nonlinear mathematical model of a blade couple mutually connected by a friction element is summarized. After that, the linearization of the mathematical model is performed by harmonic balance method. The linearized model is used for sensitivity analysis of real and imaginary parts of eigenvalues in the course of rotation and sensitivity analysis of stead-state response with respect to the design parameters of internal friction coupling. and Obsahuje seznam literatury
The paper deals with the modelling of a real gearbox used in cement mill applications and with the sensitivity analysis of its eigenfrequencies with respect to design parameters. The torsional model (including a motor and couplings) based on th finite element method implemented in an in-house MATLAB application is described. The sensitivity analysis of gearbox eigenfrequencies is performed in order to avoid possible dangerous resonance states of the gearbox. The parameters chosen with respect to the sensitivity analysis are used for tuning the gearbox eigenfrequencies outside resonance areas. Two approaches (analytical and numerical) to the sensitivity calculation are discussed. and Obsahuje seznam literatury