Journal of Machinery Manufacture and Reliability最新文献

A mathematical model of a flexible rotor interacting with a limited-power motor is considered. The rotor is modeled by an Euler–Bernoulli beam with a uniformly distributed mass and a rigid unbalanced disk. The limited-power motor is characterized by a static characteristic. The equations describing joint transverse oscillations of the rotor and its rotation are presented. The solution of the problem is presented in the form of a Fredholm integral using the Green function with subsequent discretization by trapezoid method. The results obtained demonstrate the existence of the Sommerfeld effect in the first resonance region. The influence of the motor power on the rotor “sticking” upon passing the critical speed is analyzed.

The problems of organizing the movement of a stepper drive of a three-coordinate manipulator in the remote control mode using incremental encoders integrated into the motion controller mechanism with a kinematic structure similar to that used in the actuator are examined. Control laws with different approaches to organizing the movement are considered. A single simple control law is given, the same for each of the coordinates, allowing for organizing a three-coordinate remote control without using feedback. The advantages and disadvantages of this control method are considered. Program codes for use with Arduino Uno processors are given.

The issues related to the application of a hard alloy in thrust bearings of pump sections of high-speed vane pumps, based on experimental studies conducted on a modernized test rig with a multiplier, are addressed. The tests showed that within the rotational speed range of 60–7300 rpm and a load of 1000–9000 N, a hydrodynamic lubrication regime is realized. When the bearing is stopped under load at low rotational speeds, surface damage occurs in the form of radial cracks and circumferential scratches on the inner side. The influence of high rotational speed results in the formation of vortices and hydraulic resistance in the entrance area of the oil discharge grooves, leading to oil starvation. For the use of a hard alloy bearing as part of the pump section of a high-speed vane pump containing abrasive particles in the formation fluid, it is necessary to assess experimentally the permissible magnitude of the axial force that prevents catastrophic destruction of the friction surface.

This article is devoted to the history of the development of the science of parallel structure mechanisms in Russia and abroad from the 19th century to the 1980s. The key stages in the development of this direction are considered, starting with the study of closed kinematic chains and ending with the first industrial application of parallel robots. Particular attention is paid to the contribution of domestic scientists such as P.L. Chebyshev, L.V. Assur, and N.I. Mertsalov, as well as foreign researchers, including E. Gough and D. Stewart. Important patents and inventions that laid the foundation for the further development of parallel robotics are described. This article provides an overview of the most important scientific and engineering achievements in the field of parallel mechanisms up to the 1980s.

Various types of expansion joints are used to compensate for thermal and force movements of equipment and pipelines. At gas pumping stations and power plants and in transport, expansion joints simultaneously provide vibration isolation of equipment from pipelines, foundations, and the environment. Reduction of vibration and noise transmission is necessary in the frequency range from infrasound to a thousand hertz or more. This article considers the features of thin, elastic rubber–metal elements proposed by the Mechanical Engineering Research Institute of the Russian Academy of Sciences (IMASH RAN) as elastic elements for a new type of expansion joint that improved vibration pipeline isolation by two orders of magnitude compared to commercially available expansion joints in the frequency range up to 1600 Hz. The article shows the feasibility of further improving the operational and vibration-insulating properties of expansion joints with thin rubber–metal elements due to the design and changes in the formulations of rubber, adhesives, and reinforcement material of expansion joints.

The article addresses the issue of selecting the optimal composition and production technology for the charge used in sealing rings of gas engine compressors. These rings are made from a composite based on fluoropolymer F-40 with the addition of graphite and copper-plated graphite. It is demonstrated that the properties of the resulting material depend significantly on the dispersion of the fluoropolymer particles. The study proves that heterogeneity caused by manual or mechanical mixing leads to a sharp decrease in material strength as the graphite content increases. It is established that the highest compressive strength of the composite material is achieved when the fluoropolymer particle size is within the range of 50–150 μm and the components are mixed uniformly. Furthermore, as counterpressure and surface cleanliness increase, the friction coefficient of all tested materials initially reaches a minimum and then gradually begins to rise.

A scientific and methodological approach to the construction of professional risk management (PRM) models during the construction of facilities for the oil and gas chemical industry from the standpoint of human–machine (ergatic) systems, which are considered as generalized models of organizational and technical structures of various management levels, is described. Occupational safety in such systems is based on the identification of hazards, assessment and management of risks caused by a set of parameters of the working environment and work process, and the influence of the human factor. A conceptual expert system developed by PJSC Gazprom Neft for assessing the level of funding for professional risk management activities was developed, which took into account the provision of material motivation of contractors fulfilling contractual obligations in the field of industrial and environmental safety, labor protection, and civil defense.

The possibility of using deep neural network models, in particular the U-Net architecture, for automated detection of the profile of a worn part is examined. Wear of working elements, especially in agricultural machinery, sharply reduces the efficiency of the equipment and increases the costs of its maintenance. Traditional diagnostic methods have a number of limitations, including subjectivity of assessments, the need to stop equipment, and the low accuracy of quantitative assessment of wear. A method of semantic segmentation of images using the U-Net neural network is proposed, which allows for the automatic formation of a profile of a worn part. The stages of data preparation, model training, and image analysis are described, which ensures accurate obtaining of the part profile. The effectiveness of the method was confirmed experimentally using a deep-ripping chisel as an example.

The methodology of stochastic modeling of industrial networks based on GERT networks, which eliminates the limitations of classical PERT and CPM methods by taking into account probabilistic operations, alternative paths, and feedback is discussed. A mathematical apparatus has been developed that combines graph and probability theory, as well as a modified Monte Carlo algorithm for analyzing time parameters. The Python implementation includes simulation, 3D visualization, and IoT integration. Practical tests have confirmed an increase in resource efficiency by 15–20%. The research prospects are related to the integration of GERT networks and AI to create digital twins. The results are relevant for specialists in the field of industrial engineering and management of complex systems.

An analytical model for calculating the temperature under dry external friction in conditions of longitudinal rolling (passage through one stand) of a thin strip is presented. Graphs of the calculated temperature dependences on the speed, rolling, time, and depth for a 12X18H9T steel strip are given.