Journal of Machinery Manufacture and Reliability最新文献

Hydrodynamic processes in a pipeline were studied, and a mathematical model was developed using the finite element method in the Ansys Workbench mathematical modeling package. A mathematical model of the process of gradual opening of a pipeline valve has been developed, which provides a detailed understanding of the flow dynamics and allows us to draw conclusions about the effect of the valve opening on the pressure distribution inside the pipeline.

The elements of kinematic pairs most often used in the design of mechanisms are considered. Possible primary errors for a point, line, plane, spherical pair, sliding pair, and turning pair are presented. The number of primary errors of a connecting rod with elements of two rotational pairs are calculated. Calculation of a cam mechanism is carried out. Recommendations for identifying primary errors in the mechanisms of robotic systems are presented.

In this paper, internal resonances appearing in mechanical systems with several degrees of freedom, when the ratio between the frequencies of their oscillations represent integers, are studied. As specific examples, such systems with two degrees of freedom like a double mathematical pendulum and a double physical pendulum are considered. The relationships for the oscillation frequencies of each of these systems are presented in dimensionless form depending on two dimensionless parameters characterizing the ratio between the weights of the end loads or weighty links, as well as the ratio between the lengths of the links. The conditions that should be imposed on these dimensionless parameters in order to provide for the appearance of internal resonances have been revealed. The obtained solutions are presented graphically in the form of curves on the plane of dimensionless parameters corresponding to internal resonances. In addition, a detailed investigation into the nature of these curves is presented, too. The results found upon analyzing the two problems are compared with each other. The obtained relationships have fundamental theoretical significance, which could be useful for the case of different technical applications.

The code requirements on drawing up construction design documents do not provide any method of evaluating the mechanical facilities for compliance with the requirements of a construction project. This work is aimed at determining the effective excavator radius, which ensures compliance with the process cycle set by the project. The effective radius of an excavator is the base for designing the excavator working face. A digital model describing each excavator process cycle on one extraction site (working face) has been used as the research tool. Mathematical expressions have been obtained for determining the duration of each excavator process cycle for operation on one extraction site (working face). An area for further studies is identified that consists in theoretically underpinning the position of a bucket discharge point.

Assessing the operational reliability of underground transport is important for increasing the efficiency of operation, operational and environmental safety, planning and developing a set of measures to reduce the number of failures and downtime, reducing additional financial costs and expenses, assessing and predicting operational safety, and reducing the accident rate. The obtained results of calculations of the indicators of operational reliability and technical operation of machines operating in underground conditions can be used to calculate the optimal frequency of maintenance of the main components of these machines.

This article is devoted to the design and engineering calculation of the dynamic stability of the saw blade of a new type of sawing equipment with a saw module performing a circular flat rotational–translational motion. The presented equipment relates to the field of sawing hard materials, mainly wood, but also metal, plastics, stone, bone, glass, and others. The main assembly unit of the equipment is the saw unit, consisting of six saw modules that ensure its dynamic balance without additional balancing (correction) elements.

The stage of crack propagation in aircraft structures under fatigue is of great interest. The problem of variation in the duration of fatigue crack growth is considered. Under irregular loading, durability can vary significantly. For this study, loading processes are modeled using the Markov address matrix method and several replicas of the initial process are obtained. The fatigue life of each replica is calculated using the Willenborg crack growth retardation model. A model for random processes, the TWIST sequence, which is widely used in aviation to investigate the likely scatter of durability due to the uncertainty of load information in a numerical experiment, is used as the basis for the simulation.

This article is devoted to the development of vibration technologies related to the automatic control of vibrations. The problem of controlling a two-rotor vibration machine to reproduce the mode of asymmetric vibrations is considered. The parameters of the vibration machine are chosen on the basis of the method of calculation of the dynamic factor by the exciting forces of vibration exciters. The required multiple frequency synchronization of unbalanced rotors is provided by means of an adaptive proportional-integral speed controller. The results of calculation of machine parameters for the most pronounced effect of asymmetry of the total exciting force of vibration exciters are presented as are illustrations on the results of computer modeling of the vibration machine control system for different rotational speeds and parameters of unbalanced rotors.

Modeling of the spatial low-cycle crack kinetics for refined service life and survivability of elements of aviation, rocket and space, nuclear, and other critical equipment is studied. The results of experimental studies and numerical calculations of the parameters of shape change are presented, taking into account the characteristics of the microrelief and the complex surface of low-cycle fracture of inclined surface semi-elliptical cracks. A functional relationship is shown between the mesostructural characteristics of low-cycle fragmentation of the surface of the cracks under study with parameters of nonlinear fracture mechanics such as the strain intensity coefficient and the specific elastoplastic work of fracture at a certain point of the defect contour.

Based on experimental studies aimed at studying the dimensional characteristics of titanium powders obtained for additive machines by electrodispersing OT4 alloy waste in propyl alcohol, the following were established: The average volumetric diameter of the particles is 43.3 μm. The modal particle diameter is 52.29 µm. The particle size range is 1.61. The specific surface area of the particles is 2971 cm²/cm³. The particle elongation coefficient is 1.12. It is noted that spherical titanium powder materials obtained by electrodispersing waste titanium alloy OT4 can be used effectively for additive machines.