Analysis of the Formation of Defects in the Microstructure of the M-24 Bolts of the Rubber-Cord Coupling at Various Ranges of Mileage of Electric Trains Motor Cars

This article was caused by the need to identify the formation of defects in the microstructure of the bolts of the rubber-cord coupling of the of the ER2 and ER2T series electric trains traction drive, in dependence on the cars' mileage. In the presented article, we will discuss the study of the metal structure of the M-24 bolts for the rubber-cord coupling fastening, related to the formation of defects the form of inclusions and cracks in it. The objects under study were M-24 bolts after a certain mileage, removed during the periodical maintenance and the type TR-3 periodical repair, as well as new M-24 bolts (two samples) for the rubber-cord coupling fastening.