Том 48, № 5 (2019)

Planetary transmissions have increasingly found practical application. Their rational designs containing a roller mechanism of removal of motion from planet pinions have a relatively high efficiency. The load capacity and lifetime of these transmissions are limited by the bending resistance of the involute teeth of wheels, which is in close dependence on the gear geometry, in connection with which there is the necessity to select a rational shape of teeth to reduce the stresses at their bases. It is proposed to use a modified cutting contour of wheels, which makes it possible to increase the radius of curvature of the transition curve of the tooth profile and reduce the concentration of stresses in the place of its embedding in the rim.

In this paper we consider an algorithm for solving the direct position problem for spatial mechanisms of a parallel structure with six linear drives. The direct problem is solved analytically or iteratively–numerically depending on the structural scheme of the l-coordinate mechanism. The analytical solution is based on a mathematical model of a system of three equations of lines passing through a single point. The problem of transitting from the point coordinates of the mechanism output chain to its absolute coordinates is solved. An example of solving the problem is given.

This article is about developing the mathematical model and studying the copying control system of a robotic unit with a linear electric drive with an elastic link. Particular emphasis is placed on modeling the nonlinear electric drive and measurement system devices. A comprehensive criterion is elaborated for evaluating the quality indicators of the control system. Opportunities for minimizing the influence of nonlinearities on the stability of the copying control system by optimization of parameters are studied.

The article considers the phenomenology of the topochemical kinetics of the formation and growth of adhesion cores, as one of the main processes of the kinetic approach in the theory of fracture of materials during friction. The basic provisions of the models and laws of the formation and growth of setting nuclei are investigated. Peculiarities of ideas about the processes of nucleation and the laws of their growth by various authors are considered, questions are raised that require further research in the development of mathematical models of topochemical kinetics.

To obtain analytical estimations of possible mass reduction, the simplest case of a cantilever rectangular beam loaded by a concentrated force or a distributed load is considered. Five geometrical parameters of designing are distinguished, which can be optimally defined from the five requirements: by strength, by possible accumulated elastic energy, by uniform strength, by connection of cross-sectional sizes, and by shearing force resistance owing to known strength at the interlaminar shear. The validity limits are determined, outside of which the linear beam theory leads to incorrect results for deflection of uniform-strength beams when loaded with distributed forces. The analytical dependences of reducing the desired mass of uniform-strength beams on the behavior of applied forces are the following: the more nonuniformly the applied load changes, the greater the advantage by mass ensures uniform-strength profiling under the given conditions by the strength and accumulated elastic energy.

Methodological aspects for controlling the processes that secure the reliability of a complicated machine are examined for aviation engineering and include the following: the topicality of the problem and the main problems, the characteristics of the processes for securing the reliability of aviation engineering as control objects, a way for forming the system for controlling the processes that secure the reliability of aviation engineering, a way to analyze statistical methods for controlling the reliability and the probabilistic-statistic performance of thinning flows of random events–failures detected in flight and causing on-ground operational failures, aircraft replacement, and the total number of failures and damage detected in flight and on the ground. The aim of investigations is the following: to increase the reliability and safety of flights and to increase the efficiency of aviation engineering operation.

In this paper, we study the thermal relaxation features of compressive residual stresses generated during laser-shock wave processing in high-alloyed heat-resistant Iron GH2036 alloy. A finite element modeling of thermal relaxation of the generated compressive residual stresses was performed. The features of the thermal effects on the redistribution of the compressive residual stresses in the temperature range from 200 to 650°C are studied. Based on comparative analysis, the results of the finite element modeling correlated well with the experimental data known in the literature.

An integral part of the production system is monitoring technological process. This paper proposes assessment procedures for the characteristics of process operations, making it possible to track both the failure rate of each machine and the entire system at each stage of the technological process. A process simulation model is built, describing technological processes of various durations and sets of operations, which is based on Markov modeling, when the number of different system states is finite, and variations in the system states occur at different discrete instants of time. The initial formation of a set of contingency factors in the production system is based on the Delphi approach. Using the Pareto principle makes it possible to identify the most common factors of process failures. The neural network makes it possible to simulate various situations and evaluate the probability of process violation. The procedure for the formation of a matrix of transition probabilities is proposed for both the initial assessment of the process feasibility and matrices varying discretely in time, depending on the process operation state. Based on the proposed methods, an intelligent monitoring system for machine engineering process execution is developed.