Volume 47, Nº 2 (2018)

A parallel structure mechanism with six degrees of freedom designed to operate in extreme environments is considered. A technique for searching for an analytical solution of the inverse kinematics problem and the numerical solution of the direct kinematics problem for the given mechanism is presented. Examples of these problems solutions are considered. The operating area of the mechanism is defined. The obtained results are tested successfully at a test facility.

A method for calculating the natural oscillations of a cylindrical shell of an orthotropic material is proposed. The shell is stiffened by a set of sufficiently densely positioned transverse-longitudinal ribs, the arrangement of which allows “smearing” and contains sparsely positioned discrete stiffening rings. The shell may have a closed or open cross section; it is considered to be loaded by external pressure and axial forces. The problem is reduced to a set of homogeneous algebraic equations the number of which is equal to twice the number of discrete ribs; the equation was obtained in explicit form. The comparison of the calculated and experimental data is provided.

The article presents an analysis of the stress condition of a connecting rod’s small ends. The strains acting in the most stressed section of the connecting rod’s small end are defined experimentally and using the numerical experiment. The probability of the failure of the connecting rods, depending on the acting load and conjunction clearances, is estimated. It is proposed to harden the working surface to increase the probability of a failure-free operation.

The calculated experimental procedures for determining the operating life of load-bearing locomotive structures are presented in a probabilistic form for evaluating and predicting their technical condition to provide grounds for the safe operation of locomotives. The procedures encompass lowcycle (in an elastoplastic deformation) and multicycle (in elastic deformations in the range of at least 10⁷ cycles) loading of parts.

The article describes the structure of a self-lubricating plain bearing of modified wood for heavy-loaded friction assemblies and production technology. A method is developed to define the wood’s coefficient of friction on steel and the friction machine MI–1M is upgraded. The sliding friction coefficient changes within 0.06–0.11, depending on the load.

A method to select the parameters of the processing mode of a laser additive technology for the directed growth of the complex structural elements with internal coolant passages is developed. It is demonstrated that a synergetic approach to the laser growth process based on the dynamic triunity model allows us to ensure the interrelation of the regime–structure–properties parameters. The results of the study of the structure and mechanical characteristics of the specimens obtained with the additive technology of the layer laser growth powered by the Inconel 718 alloy are presented. The criteria for the efficient application of the vectored heat input in machinery production are formulated.

The concept of a hydrogen diesel with direct gaseous hydrogen injection, despite the obvious advantages as compared to a traditional diesel, is poorly explored. In this article, the problem of the determination of the rotational charge motion intensity value in a hydrogen diesel cylinder is first formulated and solved in order to establish the limits for the emission of nitrogen oxides and the heat loads on the main parts (on a piston) of a motor under the hydrogen combustion. These parameters, which determine the environmental characteristics and the thermal stress state of a hydrogen diesel, can be regulated by varying the advance angle of the hydrogen injection under the acceptable values of the performance parameters of a motor. The optimal values (in terms of minimizing the emission of nitrogen oxides and the heat loads) of the rotational charge motion intensity and the advance angle of the hydrogen injection were determined for the case of a one-cylinder hydrogen diesel.

The physical and mechanical behavior of titanium nickelide coil springs of different stiffness is experimentally investigated during thermal cycling through martensitic transformation ranges under a constant tensile force. The springs exhibit a reversible length change by reciprocating movements. In terms of classical mechanics, a method for the design calculation of springs with shape memory as actuators is proposed for a given stiffness range.