DESCRIPTION OF SOME LINEAR AND NON-LINEAR MODELING ELEMENTS
Alford's force element
The element allows computing of aerodynamic cross-coupling forces operating
in axial flow compressors and leading to instability of rotor system. It is based
on the correlation discovered by J.S. Alford.
Wachel's force element
The element allows computing aerodynamic cross-coupling forces acting in centrifugal
compressors and leading to instability of rotors. It is based on J.C. Wachel's empirically
Block of code and elements for computation of shaft systems with gearings
This allows computing shaft systems with cylindrical, bevel, helical and hypoid
Function of import of super elements from FEM systems
The element gives an opportunity to combine solutions obtained in FEM program
and in DYNAMICS R4 by means of modal synthesis method. It allows to take into account
the complex configuration of separate assembly units, for example, cases and housings.
"Clearance" element ("Elastic Damping Lateral Restraint" element)
This element allows to model different cases of full or partial rubbings of
rotating and non-rotating structures. This allows you to model most cases of instability
in rotating systems with clearances. It takes into account any kinds of contact
with external and internal damping, with friction in contact point, weight and circumferential
irregularity of clearance. The element is indispensable to engineers' education of fundamental non-linear dynamics.
Journal bearing element
This element allows computing the rotating system with two notable cases of
plain bearing: "short" bearing and the "long" bearing. Different kinds of cavitation
of fluid film are considered: uncavitated (2-π film) damper and cavitated (π-film)
damper. It allows to compute dynamical systems in steady-state and non-steady state
Squeeze-film damper element
This element models two well-known cases of hydrodynamic damper: the "short"
damper and the "long" damper. Combinations of these cases are also possible. Different
kinds of fluid film cavitations are considered: uncavitated (2-π film) damper
and cavitated (π-film) damper. Fluid inertia effects are also included in squeeze
film damper models. It allows to compute dynamical systems in steady-state and non-steady
state conditions. Any number of squeeze-film dampers in rotating system. Fast computation.
User-programmable non-linear element
It allows to use the user's own algorithms of nonlinear effects in rotating
machinery to program new elements and also to integrate them into DYNAMICS R4 program
system. The new element can be of any complexity and it can be used in a rotor model
in combination with other non-linear elements of DYNAMICS R4. The language of
programming is the script language Python (www.python.org) built-in in DYNAMICS
R program system and can be easily mastered by the user. This element is indispensable
to engineers and post-graduate students carrying out investigations in the rotor
dynamics field. By the user's request the new element which was made in a script
language can be adapted and included in program system by DYNAMICS R4 developers
(Alfa-Tranzit Co., Ltd). It will make it possible to speed up computation dozen
Rolling bearing element
This element allows to model the main types of rolling bearings - angular-contact
(ball) bearing , roller bearing, etc. The Hertz theory is used for computing speed
dependent stiffness and bearing forces. Clearances in bearings can also be taken
into account. The user has an opportunity to specify bearing linear and nonlinear
Active magnetic bearing support element
This element allows modeling active magnetic bearing (AMB). Three main types of AMB are modeled: radial, cone and axial.
Two different input types are possible - standard(common parameters set) and expert.
Expert input parameters used for simulation of special cases and requires knowledge of the algorithm of magnetic bearings.
The model takes into account: radial clearance, maximal current and current density, electromagnetic poles number, control pole number, coil remove option.
Pole control is the axis coinciding with direction of the resultant force from the closest to it electromagnet.
Two control options are possible - PD – controller and PID – controller.
The link allows modeling of kinematic excitation of the setting foundation and appearing transient processes. One of the particular cases is the work of the setting under earthquake conditions. The element allows adjusting stiffness of the foundation with the setting in three directions and giving ground response spectra of seismic excitation from the part of the foundation. Influence is set as a polyharmonical signal acting simultaneously in three directions. Time interval of influence is divided into several ranges. They are the ranges of divergent, constant and damped amplitudes.
Individual options are offered to customers who have purchased the Dynamic R4
program system. Development of the non-linear elements can be made according
to their needs.