Journal of Machinery Manufacture and Reliability最新文献

The inapplicability of calculation methods for friction of solid bodies in the case of sliding friction on elastomers is shown. It is shown that when a solid body rubs against an elastomer, there is no running-in period and the friction is initially stationary. A method for calculating the tribological characteristics of elastomers is proposed.

Some issues in the development of a control system are considered for a manipulator with stepper actuators. For control of mechanisms with a remote center of motion, the methods to generate the control signals are presented when using unipolar and bipolar stepper motors. Examples of actuator control are given using different motion generators. The problems of development of motion generators and manipulator control methods for the simultaneous work of two or more actuators are considered.

Formulas for calculating and estimating the average residual life of nonrestorable technical objects based on the use of censored data on failure-free operating times have been proven. The results obtained can be used in problems of extending the service life of objects. Examples of estimates of the average residual life of objects are given. The average residual life proven estimates are valid for any law of life utilization of nonrenewable technical objects.

A practical method for determining a diagram when measuring circumferential strains of the free surfaces of cylinders in their stressed joints, and the deformation force characteristics of TiNi based alloys with shape memory in the range of martensitic transformations are presented.

The results of experimental and theoretical studies of the formation of a crack in a copper conductor under the influence of current overload are presented. The conductor was examined using a JSM-6390L scanning electron microscope. A refined mathematical model of the static stress–strain state and destruction of a copper rod under conditions of inelastic bending at temperatures up to 700°C has been obtained. The limiting values of the bending moment and curvature of the copper conductor, causing its rupture after the formation of a crack, have been determined. The calculation algorithm has been brought to the final analytical dependences, allowing them to be used when conducting forensic fire-technical examination or designing electrical wiring.

The article investigated the process of penetration of an aluminum plate by a steel ball at speeds from 600 to 1000 m/s. A numerical simulation of the impact of the ball was carried out and compared with the results of experiments in which the ball was accelerated using a powder accelerator. Numerical models were developed using the explicit finite element method in LS-DYNA software. The influence of material properties and model parameters on the penetration process is analyzed. A good agreement between numerical and experimental results has been achieved.

One of the promising and current trends in the design of wide span sprinkling machines is the principle of resource saving. Trends for improving the design and technological parameters of sprinkling equipment based on the principles of resource conservation are considered, and a concept for the development of sprinkling equipment based on operating conditions is formed. The research carried out made it possible to improve the truss structures of the KASKAD model range of sprinkling machines. The reduction in material consumption is based on optimizing the parameters of spans and truss structures, for which coefficients of metal consumption of the truss and the weight of angles were proposed. Improvement of the truss structure made it possible to increase the span length by 22.1–33.8% with a slight increase in mass by 5.8–15.1%.

It is shown that changes in conditions during an experiment can go unnoticed and how anomalous measurements arise that can lead to incorrect values containing gross errors. It is interpreted that distortion of measurements may be a consequence of incorrect operation of recording devices; if a fault is detected, such values should be discarded. The problems of the uncertainty of information on input data in calculations using classical methods are outlined. The influence of the deviation of external impacts from nominal values, variability of emission intensity, and the nonlinear nature of influence of external factors on the probability of an event were studied.

The problem of heat transfer during fluctuations of the lubricating layer has been studied. As a result of comparing theoretical data with experiments, one can conclude that the difference was no more than 3%. The results of the study of the fluctuation damping decrement have been presented.

The results of an analysis of the wear of a combine harvester chopper knives are presented. It is established that the maximum wear of blades is 225 hectares of harvested area, after which they should be replaced. The effectiveness of methods for blade hardening is assessed. Using changes in the hardness and microhardness of metallographic and X-ray phase analysis, the optimal blade hardening method is determined.