Failure Analysis of Cast Iron Housing Unit of Ucf-216 Ball Bearing Used in a Fully Automatic Concrete Building Block Machine

Abstract

One of the most common problems faced by briquette machine users in the industry is the failure of the cast iron housing unit of the UCF-216 bearings, to which the main shaft of the briquette machine is attached. In this study, the failure mechanism of a cast iron housing unit of a UCF-216 bearing broken during operation in a briquette machine was analysed in order to develop a solution to the problem. Failure was occurring in the bolt hole areas of the housing unit. First of all, spectral analysis was performed and it was determined that the housing unit was grey cast iron. Then, the macrostructures of both unused and damaged housing units were examined. Some casting defects were detected in the bolt hole areas of the unused housing unit. It was also learned that during the assembly of the UCF-216 to the briquette machine, no torque meter was used while the bolts were tightened. In order to understand the effect of possible overtightening of the bolts, the system was modelled as a 3D solid. This model was exported to the finite element software and different bolt pretensions were applied considering the stresses created by the bolt tightening forces on the housing unit. As a result, it was understood that if the ratio of the stress caused by the axial bolt tightening force in the UCF-216 bearing unit to the yield stress of the UCF-216 housing unit is above 50%, fatigue failure will occur.