Journal of Machinery Manufacture and Reliability最新文献

Pipeline expansion joints of various designs are used to compensate for thermal and force displacement of equipment and the pipelines themselves. Expansion joints should also ensure vibration isolation of equipment (compressor, pump, turbine, and the gas pressure reducing reducer at gas station distribution points) from the pipeline system, footings, and elements of the surrounding infrastructure and the environment in a wide frequency range from infrasound to a thousand or more Hertz at oil and gas pumping points, in thermal and nuclear power plants, and in transport energy systems. New expansion joints based on thin-layer rubber–metal elements are considered, having vibration isolation properties a hundred times better than those of serially produced expansion joints of various types in the frequency range of 30–1600 Hz. Physical models of vibration transmission through liquid expansion joints, including during the flow of the working medium, are analyzed, which when taken into account make it possible to obtain this improvement. Based on the conducted experiments and calculations, the possibilities of further improving the operational (increasing the strength and operating temperature, import substitution possibilities) and vibration isolation properties of expansion joints with thin-layer rubber–metal elements are discussed due to their design and changes in the formulations of rubber, adhesives, and reinforcement material.

This article is devoted to analysis of the influence of a constant magnetic field with an induction of 0.1 T on the mechanical characteristics of a low alloy aluminum—magnesium alloy. Mechanical tests were carried out under compression conditions, and the microhardness of aluminum alloy samples was measured without exposure to a magnetic field and after the influence of an external magnetic field. Based on the results of the experiments, compression curves were constructed in the elastic and elastic–plastic zones. The results showed that a weak magnetic field significantly affects the elastic–plastic properties of the aluminum alloy. The noticeable increase in microhardness is associated with the influence of plastic deformation, and not the magnetic field. A possible explanation is given for the observed effects.

A method for designing a compact auger for transporting cylindrical products has been developed. For the first time, the auger geometry has been determined by the specified dimensions of the cylinders it moves. The key system parameters have been identified, and a system-forming equation for the dependence of the auger shaft diameter on the dimensions of cylindrical bodies has been obtained for constructing a three-dimensional model (of the auger).

The influence of wave resonance effects on sedimentation stability and the rheological properties of dispersions based on chitosan and montmorillonite are studied. It is shown that the treatment of chitosan/montmorillonite dispersion in a wave apparatus is accompanied by a change in its structure, which is reflected in an increase in resistance to delamination over time. In addition, the superposition of wave effects leads to a significant change in the viscoelastic characteristics and dynamic viscosity of the samples. The results of this study can be used to modernize technologies for producing hemostatic materials.

The aim of the analysis and development of engineering specifications is to formulate the technical level of friction composite carbon–carbon material suitable for the manufacture of aircraft brake discs, as well as to substantiate the composition and requirements for such material formed on the basis of textile techniques. It is shown that the main characteristics that determine the quality parameters of blanks are the bulk density (filling coefficient of a blank by carbon material) and structure of the formed material.

The M/G/1/∞ system is a non-Markov model, a single-line queueing system with waiting and a Poisson incoming flow of demands of intensity λ. However, the letter G in the second place of the system entry means that the service time of each demand can be distributed according to an arbitrary law G(x). If G(x) is not hyper-Erlangian, then it is impossible to construct a process η(t) that would describe the functioning of the system and would be a Markov process with continuous time and a discrete set of states. In particular, the number of demands in the system ν(t) at time t will not be such a process, since the distribution of the remaining service time of a demand in the system, unlike the exponential case, depends on the time that this demand has already been serviced.

The research results on the composition, structure, and properties of titanium powder obtained by electroerosive dispersion of VT20 alloy waste in alcohol are presented. It is noted that the electroerosive titanium powder has the following characteristics: spherical and elliptical shapes and agglomerates; volumetric average particle diameter is 43.3 μm; particles contain C and O on the surface, while Ti, Al, and small amounts of Zr and Mo are distributed deeper in the particles; and the phase composition consists of α-Ti, TiO, TiC, and Ti₃Al.

This article presents a study of the processes of friction and destruction of grain particles in conical mills, with an emphasis on the study of thermal effects arising from their interaction with the working surfaces of the millstones. Primary attention is paid to the theoretical analysis of the temperature regime of the mill system by means of an analytical solution of the heat equation in partial derivatives using the Laplace transform.

The issues of the formation of hydraulic resistance to gas flowing through rectangular elbows of a gas pipeline, which lead to changes in the physical and chemical properties of gas and gas thermodynamic parameters, are considered. The effect of the pressure force of a gas flow on the rectangular elbow of a field gas pipeline, which is accompanied by changes in technological independent parameters, has been described. After the primary separation treatment, a gas enters the commercial gas pipeline and at this moment the gas volume expands, as a result of which the pressure drop increases and the gas movement accelerates. In practice, the higher the pressure drop, the higher the gas flow rate. In this case, the technological parameters of gas in the gas pipeline change, which leads both to an increase in the local resistance and to a change in the density and temperature of the gas.

Currently, an efficient method for pipeline inspection is in-pipe diagnostics using specialized robotic devices. There are many designs of in-pipe robots; however, they have several drawbacks: most notably, the inability to move through pipelines with complex geometries. Support-and-press in-pipe robots are the most efficient solution for maneuvering within sections of complex geometry. The aim of this research is the synthesis and development of algorithms and a control system for an in-pipe robotic complex, including the study of the kinematics of the design in sections with complex geometry. As a result, a control system structure was developed, consisting of several subsystems, including algorithms for controlling the translational movement of the in-pipe robotic complex inside the pipeline, specifically enabling movement along curved sections without loss of orientation.