Journal of Machinery Manufacture and Reliability最新文献

An approach to increasing the accuracy of technological operations using industrial robots is proposed, in which the control system of the servo drive is equipped with a position identifier.

The study is aimed at analysis of the stability of thin-walled cylindrical shells under the action of external pressure, taking into account the initial imperfections caused by corrosion. Using the example of a shell with the following geometric parameters, L = 1000 mm, R = 500 mm, and h = 5 mm, comparison of solutions of linear and nonlinear numerical simulation of buckling using the Patran–Nastran software package has been performed. It has been shown that the critical pressure calculated using the formula of R. von Mises (({{q}_{{{text{cr}}}}} = 0.341) N/mm²) is by 23% lower than the results of linear (buckling) calculation (({{q}_{{{text{cr}}}}} = 0.443) N/mm²), which emphasizes the need to take into account nonlinear effects. Particular attention is paid to the influence of a local reduction in the wall thickness (up to 1 mm) as a model of corrosion damage. It has been found that such imperfection reduces the critical pressure by 67% (to (~{{q}_{{{text{cr}}}}} = 0.146) N/mm²) even while preserving 78% of the initial thickness, which shows its high danger for the load-bearing capacity. Nonlinear analysis revealed a restructuring of the buckling failure forms and the presence of unstable bifurcation points on equilibrium curves, which are typical for systems sensitive to imperfections. The results confirm that corrosion damage more considerably reduces the stability of a shell than geometric imperfections in their own shapes. The practical relevance of this work is determined by the prediction of emergency situations, for example, the deformation of railway tanks after temperature effects. The obtained data can be used to optimize diagnostic techniques and to improve the reliability of shell structures in engineering applications.

The results of assessing the wear resistance of VT20 alloy samples subjected to ion nitriding in a gas mixture of hydrogen and nitrogen are presented. The efficiency of the developed technology is confirmed by the wear resistance characteristics of the sample surface: the wear track size of the sample is 1.23–1.28 μm; the wear groove profile depth of the sample surface is up to 5 μm; the friction coefficient is about 0.628; and the volumetric wear is 1462 × 10^–3 mm³.

A mathematical model is proposed for longitudinal oscillations in a cylindrical sample, taking into account cubic nonlinearity in the extended Kelvin–Voigt model for a viscoelastic body. The effect of nonlinear terms describing the elastic damping properties of the material exerted on the longitudinal oscillations of the sample is analyzed. The solution to the obtained nonlinear equations is constructed numerically with the use of the Galerkin method. The effect of nonlinearities has been estimated by the amplitude–frequency characteristics in the range of the first resonant frequency of the sample at different amplitudes of kinematic excitation. An algorithm for identifying the parameters of the mathematical model based on the experimental results is proposed. and a criterion for a quantitative assessment of the identifying accuracy of the sought parameters is formulated.

The influence of soil pressure on the abrasive wear resistance and wear geometry of the working surfaces of cultural moldboards of plows used in the agricultural sector is examined. Experimental studies were conducted on moldboards coated with an epoxy–sand protective layer, operated in real field conditions on sandy loam soils. Wear was monitored by measuring the diameter of spherical pits applied to the protective coating, which allowed us to assess in detail the nature and rate of wear in different areas of the moldboard surface. It was found that wear occurs unevenly, and its intensity depends on the magnitude of the local soil pressure. At the initial stage of operation of the coating, accelerated abrasion is observed, then wear stabilizes, forming a stable mode. The protective layer exhibits adaptive properties, reaching an equilibrium state of the “coating–abrasive medium” tribosystem. Research results have practical significance for the design of materials and structures of moldboards with increased resistance to abrasive wear, as well as for the development of methods for their strengthening and restoration.

A methodology is presented for experimental studies on residual stresses occurring within the surface layer in the annular grooves of critical-purpose body parts obtained by machining. It is noted that the effect of technological conditions exerted on the qualitative parameters of the surface layer in the course of machining, such as residual stresses, strengthening, and surface roughness, as applied to deep unloading slots, is poorly studied. In order to obtain correct investigation results, a design of model reference samples is proposed and the rationale for the selected calculation and experimental method for determining residual stresses is justified. The results of the studies on residual stresses obtained upon unloading model samples with the use of the experimental installation of JSC SPC TsNIITMASh through the recalculation of the measured displacements into stresses are presented.

A mathematical model of an energy-efficient thermal process during the flow of a viscous liquid in a pipeline and the implementation of the model in the Ansys Workbench software package using the finite element method are presented. Computer modeling of the resource-saving process of “hot” oil pumping and a series of numerical experiments to determine the temperature field of the energy carrier transported through the pipeline with various parameters of the additional thermal insulation layer were carried out. The results of calculations were processed in the MathCad mathematical package and presented in the form of graphical dependences that allow one to analyze the effect of thickness of the additional layer of thermal insulation on the reduced energy costs for heating oil during oil transportation.

Based on the solution to the partial differential equation of thermal conductivity by the Laplace transformation, an analytical model for calculating temperature under conditions of velocity and shear oscillations under dry sliding friction was obtained. In the form of graphs, the calculated dependences of temperature on the amplitude of oscillations, time, and depth for 12Kh18N10T steel are given.

The results of a study of the distribution of deformations during the destruction of a steel sample with a crack using the thermal control method are presented. The methodological basis of this study (determining the characteristics of the distribution of local stresses) was the use of methods of fractal theory, image clustering, and the calculation of the statistical characteristics of temperature distributions in the sample during loading. This study was based on thermoelastics, thermoplastic effects, and digital image processing.

This article discusses increasing surface microhardness by ultrasonic diamond burnishing. To conduct the experiment, an ultrasonic installation has been used for simultaneous diamond burnishing and deposition of a solid antifriction coating on the end faces of a sample. A full factorial experiment is used for this study. Based on the regression dependence, changes in the microhardness of the processed surface due to the ultrasonic processing parameters are revealed and the corresponding plots are constructed.