Volume 46, Nº 4 (2017)

The paper deals with the problems of kinematic and force analysis of a technological robot with a parallel structure, which is a development of the well-known METROM scheme that corresponds to five degrees of freedom. In contrast to the prototype, this mechanism only has three kinematic chains, which leads to an increase in the working area due to a decrease in the possibility of mutual interference between the kinematic chains.

An engineering system of complex real machine assembly is considered that, in contrast to a conventional assembly, has additional degrees of freedom. These degrees of freedom are considered to be latent, i.e., those that modify the dynamics of the basic degree of freedom on average. According to this approach, the authors obtained an averaged equation that has the form of a classical equation of a simple real assembly, but contains an additional moment of load that considers resonance phenomena. The derivation of the equation is exemplified by a vehicle that moves along an uneven road.

The resonant behavior of multidimensional structures simulated via strongly nonlinear dynamic systems has been studied. The energy balance principle has been applied for the qualitative analysis of these systems. The number of potential nonlinear resonant modes under periodic polyharmonic force and parametric excitation has been estimated. The dynamic effects have been investigated and examples have been provided.

The results of an experimentally calculated study of f low-type hydrodynamic oscillators of the vortex type have been presented. The work objective is to research the inf luence of oscillator geometry, in particular the positions of holes that feed the working substance, on the amplitude–frequency responses. These oscillators are applied in wave techniques used in mechanical engineering, the chemical industry, power engineering, oil and gas production, and a number of other industries.

A methodical approach to estimating the accuracy of the stressed-deformed state of structural elements has been presented that consists of the reverse analysis of errors in analytical and numerical solutions. The novelty of the approach lies in defining the problems of comparing analytical and numerical results jointly with the developed method for estimating the computational errors. The approach makes it possible to increase the validity of computation results according to the applied computation procedures, which makes it possible to increase the reliability and safety of technical objects.

The relationship between the wear rates of materials and the hydrogen formation in the friction zone has been confirmed based on the working hypothesis. A study has been performed in order to identify the correlations between these processes for different materials of parts for fuel pumps and different lubricating media. Regression equations have been proposed.

This paper proposes a dynamic model of cylindrical grinding with a tool owning specified distribution of abrasive grains. Cutting forces have been calculated, the surface geometry formed after a grinding wheel pass has been determined, the influence of the process dynamics on cutting forces and machined surface geometry has been taken into account, and the effects of cutting condit on vibrations being generated in the process of grinding have been investigated.

A system and algorithm for controlling a complex flexible rotor on active magnenic bearings have been proposed that make it possible to significantly reduce the amplitude of rotor vibrations at critical frequencies. The algorithm combines the identification of the forces of inertia caused by the residual imbalance and the formation of control actions compensating these forces. The effectiveness of the synthesized control system and control algorithm has been illustrated by computer simulation.

The operating experience of prototype pit excavators has been overviewed. The reasons for the failures of machine elements in hydraulic systems, working equipment, and swivel platforms have been analyzed. The results of full-scale testing of metal structures and hydraulic systems of machines have been presented. Based on the performed studies, recommendations have been given for the lifetime determination of operating machines.