Volume 45, Nº 3 (2016)

Design diagrams of wave gears with external deformation wave generators based on a parallel crank mechanism are considered. Wave gears can be used to develop new drives with a high-quality rating in terms of efficiency, kinematic accuracy, torsional stiffness, and interesting layout solutions. In order to obtain the best possible ratings of these gears, it is necessary to determine if there are redundant constraints in the design and to reduce (or eliminate) them. To do this, one of the modern structural analysis methods, the graph method, is used. It makes it possible to find circuits with redundant constraints and reasonably eliminate them. The simplicity and illustrativeness of the method are shown.

Problems of simulating the processes of exoskeleton sit-to-stand movement are considered. A mathematical model of the device is described. The diagram of an automatic control system is proposed, based on the ZMP method. The results of the mathematical simulating are given. It is shown that the proposed control system makes verticalization possible without falling from a wide range of initial conditions.

The interaction of a rotor with a stator without separation is considered during their plane-parallel motion and under assumption of constant rotor speed. In contrast to known papers devoted to the problem of the possibility of rolling in the rotor system, it is shown that the retrograde precession frequency is always lower than the inherent one, which corresponds to a zero-clearance flexible–mobile stator system.

Problems related to the stability of the eccentricity identification algorithm in the problem of balancing flexible rotors are considered. The accuracy of the algorithm developed for identification by static influence coefficients is studied. The physical meaning of the condition number in the eccentricity identification problem is revealed. Optimal relationships are established between the balancing accuracy, the precision of measurement instrumentation, and the dynamic model of the system under consideration.

We study the possibility of accounting for the influence of residual stress in structural elements of a high-duty item on the strain–stress state and predicting the residual life of cyclical strength throughout the entire part for an extension of the safety period. Checking calculation of the static strength checking by computer simulation reveals that the influence of residual stress on the stress field from the external load is more difficult to determine than by simple algebraic addition. It is shown that the part under the action of external cyclical stresses with the maximum peak intensity of external stresses should be considered as a structure under multicycle fatigue conditions, since the intensity of total (external and residual) stresses is higher than the endurance limit.

In [1–10], devoted to theoretical analysis of finite-length porous bearings working in non-steady-state regime, it is assumed that the gap is completely filled with lubricant material. In addition, bearing structures considered in this work possessing damping properties have low bearing capacity. Therefore it is necessary to make bearing structures so that the bearings have both damping properties and higher bearing capacity. Existing computational models of composite bearings [10] assume complete filling of the gap with lubricant material. Two cases of supplying lubricant material (axial and radial) are considered in turn. This work presents a solution to the problem of partial filling of lubricant material without allowance for its supply.

The paper presents the results of studying the structure and physical and mechanical properties of a Ni–Co–Cr–Al–Y heat-resistant intermetallic compound coating, formed by the method of the high-energy plasma powder spraying on the working surfaces of turbine blades of a gas turbine engine in the initial state and after completing the designed resource (within ~28000 h), as part of a GTE-45-3 power unit of a thermal power plant (ОАО Yakutenergo).

The results of structural calculations for the cooling of a cylindrical crystallizer in a continuous casting machine for steel molds are given. The material for crystallizer walls has been replaced. The novelty of this study has been validated with an invention patent.

The problem of applying magnetorheological fluids in damping systems of shock loadings is considered. The physical prerequisites of controlling the characteristics of magnetorheological fluids with internal electromagnetic fields are examined. Processes occurring in magnetorheological fluids under shock loadings are studied. The criterion for selecting a magnetorheological fluid for such problems is the appearance of electromagnetic pulses on windings of solenoid designed to generate an internal controlling magnetic field. The amplitude and duration of these pulses is a function of shock loadings. It is necessary to take their influence into account when developing magnetorheological dampers for shock loadings.

Estimation of the reliability and safety of Arctic pipelines is associated with the fundamental necessity of taking into account the simultaneous action (combination) of natural and technological loads in the form of random time processes. Practically all existing methods for calculating reliability under the action of load combinations are in the form of random variables, which greatly limits study of the reliability of these systems with time. The methods considering loads as random processes evaluate reliability based on statistical dynamics equations. This requires considerable simplification of the initial mechanics problem, including due to the nonlinearity of the limit state function. The result, which can only be obtained numerically, turns out to be very rough.