Journal of Machinery Manufacture and Reliability最新文献

A scientific approach based on analysis of the acoustic noise intensity, based on the theory of mathematical series, which made it possible to solve successfully the problem of assessing the error of results obtained when conducting experiments to find sound insulation parameters, is presented. Identified patterns found their application in the process of designing a special structure for an experiment.

This article considers the application of digital technologies in repair agencies, considering several peculiarities, such as heterogeneous manufactured output, unsteady manufacturing as well as detailed checkout, application of the process-based approach together with automated control systems, automated preproduction engineering, equipment control and information collection, and enterprise management. The unified information environment formed by these systems reduces the number of incorrectly rejected and accepted parts by 75–80% and excludes wrong repair decisions and reduces the time needed for decision-making.

The essence of the proposed methodology for monitoring the kinetics of damage to a deformed material is to establish a correspondence between micro-, meso-, and macrodamage, and the acoustic emission pulses generated in this case. During the loading process of a product, the recorded pulses are divided into pulse flows of low (H), middle (C), and high (B) energy levels, corresponding to the energy of destruction of structural bonds. By calculating the current values of the partial content of acoustic emission pulses in the H, C, and B clusters generated by micro-, meso-, and macrodamage, and comparing them with the threshold ones established during destruction, the load-bearing capacity current level of a product during loading is determined. Application of the developed methodology for identifying zones of developing damage and assessing the load-bearing capacity of the current state of stringers under loading conditions during interlayer shear tests is considered.

The processes of elastic and elastoplastic deformation in concentration zones are analyzed for the case of different levels of rated stresses and resistance with respect to plastic strains. Based on the calculated and experimental data, it is shown that, with a decrease in the strengthening index in the inelastic region, the inhomogeneity of the strain distribution exhibits an increase. At the same time, the strain concentration coefficients increase and the stress concentration coefficients decrease. Special cases are considered when the latter are less than unity. This is important for justifying the strength, service life, survivability, and safety of new objects of the technosphere made of special structural materials and operated under extreme thermomechanical loading conditions, including the conditions inherent in nuclear power plants in normal modes and emergency situations.

The concept of a spacecraft for collecting space debris assumes that its orbit continuously changes in relation to the location of space debris in various orbits. The highest density of space debris, which is 10^–6 t/km³, is observed at orbital altitudes of 800–1000 and 1400–1500 km with an inclination of 60°–80°. To this end, stable trajectories in the sense of Zhukovskii should be determined. We propose a method for selecting the orbit of a space debris collector, including a robotic spacecraft, using the theorem on the stability of trajectories in the sense of Zhukovskii.

The formation and development of cracks in samples made of ferromagnetic material, cast iron grade SCh 35, which are in a uniformly magnetized state under the influence of an internal magnetic field with a strength of more than 20 kA/m, has been studied. The anisotropic nature of quasi-brittle fracture and the magnitude of mechanical stresses at which fracture occurs are shown. Cracks propagating along magnetic field lines dominate. A possible reason for this is the magnetic interaction between the surfaces of the microcrack.

Theoretical calculations of the residual silicon content in the structure of reaction-sintered silicon carbide are provided. The dependence of the bending strength on the initial carbon content is established experimentally. The rational fractional composition and amount of the carbon component are determined to obtain silicon carbide ceramics with maximum increased strength.

It is shown that junctions between rubber seals and shafts should have specified durability parameters in order to provide the tightness of the assembly unit wherein they are mounted. The necessity and importance of performing bench testing of reinforced rubber seals connected with shafts are substantiated. A description of the design of a special test bench for the accelerated testing of reinforced rubber seals connected with shafts is presented. The results of the accelerated bench testing of 1.1–45 × 65 seals corresponding to GOST (State Standard) 8752-79 in junction with shafts made of 45 grade steel are presented. It has been revealed that minor leakages occur from the very beginning of operation of the junction, and then, as the operating time increases, the leakage magnitude exhibits an increase. The main factor affecting the increase in leakage consists in the junction tightness that decreases owing to the wear of parts.

The principle of media separation bearing design is presented. Experiments to evaluate the performance of such bearings in the rotor axial unloading unit of a labyrinth screw pump are described.

The characteristics of thin-walled samples made of the 8011 aluminum alloy and Kh18N9T stainless steel after double-sided ultrasonic hardening of the surface layer are presented. The dependences of the change in the yield strength and the relative elongation of the sample layers made of the aluminum alloy 8011 and stainless steel Kh18N9T after their rupture on the depth of the strengthened layer are presented. The results of cut tests with ultrasonic sample hardening are presented. The coefficient of increase in the axial strength of the samples after ultrasonic hardening is determined. The microstructure of a sample section made of aluminum alloy 8011 with and without double-sided ultrasonic hardening are presented. It is shown that the microstructure changes after double-sided ultrasonic hardening, nanostructures appear at a depth of 20–30 µm, and the particle sizes are 40–80 nm.