Excitation of low-frequency vibrations and their propagation

In putting into production various new technologies, often for the forced excitation of vibrations special vibration machines, which are used in the product formation technology, are applied. The paper deals with the vibration excitation source, which is used in the production technology of construction blocks, their mass compaction. The measured parameters of vibrations show that local insulation of vibrations caused by the vibration machine is not sufficient. Theoretical and experimental investigations showed that despite of the application of standard methods, for reducing vibrations, propagated by them, the transversal and longitudinal waves, excited by vibrations are propagating through the constructions of the buildings and the ground with low extinction losses. Those harmful vibrations propagating into the environment reach the living zones and cause considerable problems for human work and recreation. Having studied the ways of vibration propagation, some were proposed and some implemented in the specific object. The data of the works performed provided in the paper show that in order to protect objects and people from the harmful impact of vibrations, while designing such plants it is necessary to implement the new methods for vibration reductio

Dem analysis of effect of the particle size during the material flow in wedge-shaped hopper

"The current analysis was mainly focused to the study of the strained physical effects arising from a decrease of the particles number. The main aspects concerning programming concepts as well as languages having influence on the computer time of simulations is also presented. The limitation in the particles amount was adopted by increasing the particle radii to keep constant the total mass of granular material. In this way, the performed computer simulations of the filling and discharge in three-dimensional hopper using 1980, 10000 and 20400 number of particles were shown that the decrease in particles number with increasing the particle radii produces an artificial friction due to material homogeneity. This is results in the decreased mass fraction and its rate during discharge causing the longest time for the full material discharge; the decreased normal and increased shear pressure of walls

Comparable analysis of vibrodiagnostic results of rotary components with different type bearings

"Comparable vibrodiagnostic results of rotor components of technological machines with bearings of tilting-pad journal bearing, sleeve liquid-friction and of roll are given in this work. Sliding of roll of researching technological machines are described; the main characteristics of work and photo are given. Experimental comparable vibrodiagnostics measurements are done. Primary signals of measurement are gotten doing vibrodiagnostic measurements, using different programmable pockets they are transformed to other formats of data. Getting results of measurement are systematized and its analysis is done. Comparison of getting results is done and dependence of work characteristics between rotary systems with bearings of sledding friction and of roll is ascertained. Generalization of results of vibrodiagnostic researches is done and conclusions are formulated in the end of this work

Method of dot mappings in measurement of dynamic parameters of rotary systems

The method of integrated continuous measurement of dynamic parameters of rotary systems is based on natural interrelations between these parameters, which are implied by fundamental mechanics laws, and also on direct measurements of those parameters, which permit such measurement. An integrated continuous measurement of dynamic parameters envisages a direct measurement of distances sij up to points on a rotor surface also measurement of linear speeds Vij of these points by three sensors Dij (in each supporting plane). The equations system, which allows determining positions and size of radiuses-vectors rij, and also instant positions of a rotation axis and a symmetry axis of a rotor and instant values of its angular speed, may be made up and solved according to results of such measuring. It is obvious that instant values of parameters, which are determined by direct measurement, by the solution of the equations system and the subsequent calculation (at the solution of an inverse problem), are dot mapping of an instant condition of rotary system. The information, which accrues in computer memory at multiple recurrences of the listed above actions during each rotor revolution, represents the dot mapping of dynamics of rotary system during all work cycle. We can assume that the dot mapping of rotary system dynamics will allow applying simultaneously with identification of dynamic parameters a method of full bifurcation groups for the full analysis of a condition the rotary system, including nonlinear conditions and interim steady states, which these nonlinear conditions generat

Rare events – rare attractors; formalization and examples

Analogy between attractors in nonlinear dynamics, called “rare attractors” by M.V. Zakrzhevsky and his colleagues [1] and emergencies, such as natural and technogenic catastrophes as well as downfalls caused by risky economic policies and strategies has been discussed. Examples of rare but technically significant attractors in nonlinear dynamics have been give

Lyapunov quantities, limit cycles and strange behavior of trajectories in two-dimensional quadratic systems

"The computation of Lyapunov quantities is closely connected with the important in engineering mechanics question of dynamical system behavior near to ""safe"" or ""dangerous"" boundary of the stability domain. In classical works for the analysis of system behavior near boundary of the stability domain was developed the method of Lyapunov quantities (or Poincare-Lyapunov constants), which determine system behavior in the neighborhood of the boundary. In the present work a new method for computation of Lyapunov quantities, developed for the Euclidian coordinates and in the time domain, is suggested and is applied to investigation of small limit cycles. The general formula for computation of the third Lyapunov quantity for Lienard system is obtained. Transformations between quadratic system and special type of Lienard system are described. The computation of large (normal amplitude) limit cycles for quadratic systems such that the first and second Lyapunov quantities are equal to zero and the third one is not equal zero were carried out. In these computations the quadratic system is reduced to the Lienard equation and by the latter the two-dimensional domain of parameters, corresponding the existence of four limit cycles (three ""small"" and one ""large"") was evaluated. This domain extends the domain of parameters obtained for the quadratic system with four limit cycles due to Shi in 1980