Failure analysis of eccentric bushings in large gyratory crusher

Abstract

Shortly after the start-up of the loaded gyratory crusher, a severe failure issue occurred in the eccentric bushing of the crusher. Based on the analysis of working conditions and force, the failure mechanism of the eccentric bushing is studied in detail by combining macroscopic analysis, finite element analysis, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The macroscopic analysis results indicate that the failure of the eccentric bushing occurs at the contact position with the mantle shaft, where strong oxidation takes place. The finite element analysis results show that stress concentration occurs at the contact position between the eccentric bushing and the mantle shaft. Nevertheless, the maximum von Mises stress in the eccentric bushing remains significantly below the material's yield strength. Furthermore, the maximum deformation of the eccentric bushing is minor. Therefore, the failure of eccentric bushings is not caused by insufficient material strength or large deformation. It should be noted that the finite element analysis results show that the minimum clearance δ between the beam bushing and the mantle bushing has a great influence on the contact position between the eccentric bushing and the mantle shaft. SEM and EDS analysis of the undamaged samples indicate the presence of numerous micro-pits on the surface of the eccentric bushing. Meanwhile, a large amount of sulfur and oxygen elements and their chemical compounds are found on the fracture surface, exhibiting local enrichment phenomena. The SEM and EDS analyses conducted on samples around the crack reveal pronounced corrosion and spalling phenomena on the surface of the lead-tin bronze alloy. The comprehensive analysis shows that the failure of the eccentric bushing is mainly due to sulfur contamination, which leads to sulfidation and oxidation under elevated temperature conditions, thus promoting corrosion and corrosion-induced cracking.