Journal of Machinery Manufacture and Reliability最新文献

The vibrations that arise in a system when several rotors with a small spread of dynamic characteristics are mounted on the elastic base are studied. Symmetrical frame structures with both linear and nonlinear elastic characteristics are considered as a base. It is shown that, in these systems, the interaction of different vibration modes occurs due to the low asymmetry, and unstable resonance modes with sharp jumps in vibration amplitudes occur at certain rotor rotation speeds. A system consisting of four rotors mounted on an elastic square shock-absorbing frame is analyzed. The conditions for the occurrence of unstable modes and the most dangerous rotor rotation speeds are found. The calculated and theoretical results are given. The mathematical apparatus of the theory of representation of symmetry groups is used for analytical studies of a symmetric system.

The patterns of destruction of an abrasive and the walls of the channel of a nozzle attachment of a waterjet machine during the movement of a multiphase flow modified by surfactants are revealed. The results of modeling the kinematic characteristics of the motion of abrasive particles in a multiphase flow with surfactants, as well as the results of modeling the contact interaction of the abrasive with the walls of the nozzle of a waterjet machine are presented. Conclusions are made about the influence of the geometry of the nozzle channel profile on the destruction of the abrasive and the surface of the jet-forming channel.

Data on the reaction of the human body to the heat impact of woven electric heaters are obtained. To estimate the reaction results, the data are processed considering the calculation of the difference between the temperatures obtained in the heater area with variable and constant heat transfer coefficients to the human body. The obtained results are compared with those of the peripheral microcirculation study using plethysmography and laser Doppler flowmetry. The comparison shows both the coinciding and the original nature of the results; therefore, the proposed approach can be used independently and be combined with other methods, which will allow us to obtain more information about the effect of heat on the microcirculation processes of blood. This article is useful for experts developing heating devices for humans and medicine, as well as for physiologists and medical workers.

Several energy parameters of molecular models of polytetrafluoroethylene and its composite F4K20 are calculated. As a result of friction and wear modeling, the energies of intermolecular bonds in the volume of the constructed (U_{{{text{inter}}}}^{{text{V}}}) models, in the surface zone (U_{{{text{inter}}}}^{{text{S}}}), and at the transfer layer–counterbody interface are determined, and the shear moduli of the material models under study are assessed. It is found that, in F4K20, compared with the original matrix, all of the above parameters increase, which may indicate stabilization of the kinetic state of molecules in the presence of a filler. Based on the results of a comparative analysis of (U_{{{text{inter}}}}^{{text{V}}}), (U_{{{text{inter}}}}^{{text{S}}}), and (U_{{{text{inter}}}}^{{{text{ad}}}}) with the value of the linear wear rate determined for the materials under study as a result of tribological tests, the (U_{{{text{inter}}}}^{{text{V}}}) value is proposed as a wear-sensitive criterion at the molecular level, and the (U_{{{text{inter}}}}^{{{text{ad}}}}) value is proposed as an additional parameter characterizing the adhesive strength of the transfer layers.

The bending and vibration characteristics have been investigated of the piston pin of internal combustion (IC) engine using where ANSYS 17.2 software. Piston pin is the main component of IC engine’s piston connecting rod assembly; which play a crucial role in transmitting gas force from piston to connecting rod to crankshaft. Design of piston pin needs the awareness of various boundary conditions, loading conditions and developed stress resultant (N_xx, N_yy, N_xy). It is also desires the information of materials, various types of surface treatments to increase its fatigue strength and avoid various modes of failures. Here, bending behavior of piston pin has been studied under mechanical and thermal load conditions after that analyzed the various stresses such as shear stress (τ_xz, τ_yz) and bending stress (σ_xx, σ_yy, σ_xy). Moreover, the empirical formulas for piston pin geometry, clearance, importance of piston pin offset, and complete design procedure of IC engine piston pin is expressed. In this communication the effect of various boundary conditions (fully floating piston pin, semi floating piston pin and stationary piston pin), loading conditions, material properties (Material 1–4), inner cross section of piston pin has been investigated.

When designing thin-walled structures made of composite materials, the fundamental initial data are the unidirectional layer characteristics which depend to a large extent on the properties of the matrix and its adhesion to the fiber. In this paper, using the Rabotnov nonlinear constitutive relation, the regularities of deformation of a unidirectional carbon fiber-reinforced thermoplastic at high temperature under in-plane shear conditions are described. The application of the properties of resolvent operators used in hereditary mechanics of solids and the choice of approximation of the instantaneous stress–strain curve made it possible to invert the Rabotnov constitutive relation. Comparison with the experimental results showed the correctness of the proposed approach.

A simplified method for calculating the secondary field in the far field of a finite cylindrical shell immersed in a liquid is proposed. A comparative assessment of the components of the total field associated with radiation caused by shell vibrations and sound reflection from an absolutely solid body is given. Recommendations for the use of the simplified method are given.

Based on the processing of a backscattered electron digital image of the ground surface and the results of X-ray spectral microanalysis, a method for determining the intensity of titanium alloy charging by wear products of an abrasive tool made of silicon carbide is developed. The numerical values of the charging intensity and the laws of its distribution are determined. The effect of radial feed on the charging intensity is established.

Mechanical transmissions with noncircular gears are of interest to researchers, inventors, and engineers due to the high compactness of such mechanisms, as well as the implementation of a wide range of transmission functions. The kinematics of a planetary transmission with internal engagement with oval gears, which allows the implementation of reciprocating rotational motion of the output shaft, are examined. A kinematic model of the mechanism was constructed, and the law of motion was determined in the form of an analogue of the speed and position function of the output link. An experimental setup of the proposed planetary transmission has been developed, on the basis of which the position functions for three variants of the mechanism with different kinematic parameters have been investigated. Statistical analysis of the measurement errors showed the adequacy of the constructed kinematic model, which allows using it in future dynamic, power studies and the design of machines based on the proposed planetary transmission.

Spatial vibrations of a pipeline with vibrating supports were investigated. The pipeline transports a gas–liquid medium with an annular structural flow pattern. The flow of particles of a gas–liquid mixture in the cross sections of an accelerated pipeline is taken into account. A comparative analysis of the results of calculations obtained from the analytical solution of linearized and numerical modeling of nonlinear equations of steady-state bending-rotational vibrations of a pipe is given. The influence of the internal attached mass of the transported product on the values of the natural frequencies of the first form of bending and angular oscillations of the pipeline is shown.