Journal of Machinery Manufacture and Reliability最新文献

Variants for complete damping of the scattered and diffraction sound field of a cylindrical shell are considered, and calculation results obtained for the diffraction field damping are presented.

In the article the parametric oscillations of an unreformed disk located in a contactless electromagnetic suspension with an electrostatic loop of the effective control stiffness were investigated analytically. The analytical expressions for the transition curves of the stationary position of the levitated object were obtained based on the asymptotical method of nonlinear dynamics for the areas of the main and secondary parametric resonances. The system parameters were estimated for which the contactless suspension with quasi-zero electromagnetic stiffness is asymptotically stable.

This article discusses the issue of automating the process of transportation and orientation of canisters on a conveyor. The design of the mechanism for turning canisters on a conveyor has been developed; kinematic studies and strength analysis of the main units have been carried out. A 3D model of such a mechanism has been created, and the principle of its operation has been described. The algorithm of operation of the automated control system for the transportation and orientation of canisters is considered.

The principles of welding with pressure for making nuclear reactor components from refractory nickel alloys with limited weldability are presented. The main focus is placed on gasostatic diffusive welding with additional surface treatment (laser surface modification and profiling by machining). It is shown that the modification of welded surfaces allows making the breaking strength of the weld joint at room temperature closer to that of the base metal.

This article considers the experience in arranging and conducting gas dynamic tests of model self-separating fuel element bundles made using additive technologies. The models consist of helical rectangular-sectioned rods of 4.8 mm in specified diameter and 2.5 mm in width and differ by the coiling pitch and rod production technology, including 3D printing modes and surface treatment. The models are tested at the aerodynamic test bench of the Department of Nuclear Reactors and Facilities of Bauman Moscow State Technical University. The data about the static pressure distribution along and around the perimeter of the model jacket are used to calculate the hydraulic characteristics of bundles in the Reynolds number range from 2.8 × 10³ to 6.8 × 10³. It is shown that the rod production technology determining the quality and roughness of the surface has a significant effect on these characteristics.

It was established that the key operational factor that shapes the service life of aircraft wheels is the nonstationary nature of the operational load spectrum; typical characteristics of the nonstationary spectrum for aircraft wheels were determined—distances of movement at individual stages of ground movement and the degree of influence of lateral loads during typical maneuvers. It was shown that, under such conditions, to predict the service life, it is necessary to use phenomenological theories of damage accumulation that describe the kinetics of fatigue failure. A probabilistic model for predicting the service life of aircraft wheels was developed, which takes into account the stochasticity of service life indicators and makes it possible to obtain, by calculation, reliable estimates of the maximum time to failure in the conditions of limited information about the durability of full-scale wheels.

The results of assessment for the current technical condition of one of the complicated rotary-type machines with the use of a technology based on nonstandard methods of vibration monitoring and machine diagnostics developed at the Mechanical Engineering Research Institute of the Russian Academy of Sciences (IMASH RAN) are presented. Using the developed technology based on data obtained under perennial rotor unit operation, incipient defects have been revealed, and the process of changes in the unit vibration condition have been traced using S-discriminants. In addition, the time dependences of spectral amplitudes have been constructed to identify developing defects by calculating the stochastic interrelation between the time dependences of different vibration parameters, and an assessment of the current technical condition for such a unique machine as a moving neutron reflector has been carried out.

When using the novel innovative technology of laser shock forming, a laser shock wave causes a bending deformation of the plate. Simulation of the technology of laser shock forming by the finite element method has been carried out. The following two mechanisms of plate bending have been investigated: a stress-gradient bending mechanism and a stress-bending mechanism. It has been established that the actualization of a specific plate bending mechanism depends on the ratio between the main parameters of laser shock forming: the laser spot overlapping coefficient, the number of repetitive laser pulses, and the laser power density. Four different modes of plate bending have been studied, which differ from each other in the depth of the plastic deformation zone at the site of interaction between the laser radiation and the material. It is shown that the plate thickness is of decisive importance, too. The tensile force, the bending torque, and the curvature of the plate depending on the overlapping coefficient of laser spots have been obtained. The results obtained show that the curvature of the plate calculated with the use of the finite element method is in good agreement with the experimental data.

Ensuring constant tape tension and the absence of sagging in machines and equipment using rolled materials determines the quality of the resulting products. Based on an analysis of the known solutions, a new mechanism for unwinding and pulling rolled material is proposed. Static and dynamic analysis showed that the developed device provides a constant tension force for the wound tape of material and does not allow sagging and inertial runout of the roll. In addition, the created mechanism makes it possible to reduce jumps significantly in the tension force of the tape during acceleration and deceleration of the broaching drive.

Based on the solution of the Fourier heat equations in partial derivatives, analytical models to calculate temperature during friction and impact are derived. The calculations performed demonstrated the adequacy of the models for the experimental data. Models of the coefficient for sharing the heat flow are reviewed.