https://doi.org/10.25198/2077-7175-2020-3-135
THEORETICAL JUSTIFICATION OF RELIABILITY OF THREADED CONNECTIONS OF CARS DURING OPERATION
Yu. V. Rodionov, S. V. Karpukhin, S. V. Sumenkov
Penza State University of Architecture and Construction, Penza, Russia
e-mail: dekauto@pguas.ru
Abstract. The reliability of threaded connections is determined by the strength of their tightening, which, in particular, depends on the presence of defects and impurities in the material structure of the mated parts. In the case of intense vibrations, vibrations with alternating stresses occur, causing not only the movement of dislocations and defects, but also activating the penetration of various impurities. Based on the results of our own research, it was found that the weakening of the initial tightening of screws in the nodes of domestic passenger cars is the cause of one-third of equipment failures. It is emphasized that issues related to monitoring and ensuring the stability of the tightening of threaded connections in conditions of vibration effects should be considered in conjunction with the features of the material structure. The goal of the research is to improve the reliability of vehicles and other transport and technological machines by developing technological and structural solutions related to the manufacture and operation of units and assemblies with threaded connections.
Based on the consideration of the local dislocation pet model with the Cottrell cloud, it was determined that a decrease in the elastic modulus leads to an increase in the bolt’s pliability coefficient and, consequently, to an increase in its deformation under vibration conditions. This inevitably causes a reduction in the pre-tightening force of the thread connection. It is believed that the deformation and pliability of the bolt is largely determined by the dynamics of the inhomogeneous structure of the metal in the operating conditions of cars. It is assumed that the main influence on the pliability of the bolt is provided by mobile inclusions with a significant diffusion coefficient. It was found that, taking into account the time-dependent correction, the forced diffusion of extraneous inclusions is similar to free diffusion. In this case, the length of the impurity change is comparable to the size of the Cottrell cloud, that is, during repeated loading, the length of the dislocation segment actually remains unchanged. This is true for a certain value of the diffusion coefficient, at a higher value of which the stability of the elastic modulus will be violated with increasing length of the dislocation segment, the maximum possible change of which may be approximately ten percent.
The proposed model showing the weakening of the tightening of threaded connections under vibration conditions is correct for connections made using chip removal methods, because the dislocation density depends significantly on the technological method of thread formation.
As a result of further research, it is planned to propose a new design solution at the level of the patent of the Russian Federation to ensure the stability of the tightening of the threaded connection under vibration conditions.
Keywords: vehicle, operation, failsafe, threaded connection, dislocation, impurity, vibration, Cottrell cloud.
Cite as: Rodionov, Yu. V., Karpukhin, S. V., Sumenkov, S. V. (2020) [Theoretical justification of reliability of threaded connections of cars during operation]. Intellekt. Innovatsii. Investitsii [Intellect. Innovations. Investments]. Vol. 3, pp. 135–141. DOI: 10.25198/2077-7175-2020-3-135.
