Archives du mot-clef Bucket Wheel Excavator

Failure Investigation of the Bucket Wheel Excavator Crawler Chain Link

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The high mobility of open pit machines in heavy duty conditions provides fertile ground for the occurrence of various failures of the traveling mechanisms’ vital parts such as chain links. The goal of the study presented in this paper was to diagnose the cause of the damage of the bucket wheel excavator crawler chain links. In order to identify the reasons behind chain link failures, stress state calculations were performed as well as experimental investigations which, given the nature of the failure, included visual and metallographic examinations, chemical composition analysis and tests of mechanical properties. Based on the results of the numerical-experimental analyses, it was concluded that the chain link breakdowns are caused by ‘manufacturing-in’ defects. The results of the presented analyses also emphasize the importance of a comprehensive quality control of chain links.http://www.sciencedirect.com/science/article/pii/S1350630713001611

Failure Analysis : Analysis of the drive shaft fracture of the bucket wheel excavator

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ScienceDirect – Engineering Failure Analysis : Analysis of the drive shaft fracture of the bucket wheel excavator.

Mile Savkovića,, Milomir Gašića, Dragan Petrovića, Nebojša Zdravkovića, Radmila Pljakićb

a University of Kragujevac, Faculty of Mechanical Engineering Kraljevo, Dositejeva 19, 36000 Kraljevo, Serbia
b Laboratory for Testing of Materials High School Trstenik, Radoja Krstića 19, 37240 Trstenik, Serbia

Abstract

Drive in most bucket wheel excavators (BWE) is accomplished through its electric motor, cardan shaft and planetary gearbox. In the BWE SchRs630/6×25, the planetary gearbox is cantilevered at the end of the hollow shaft which transmits the torque through the sprocket to the caterpillar track chain. In this BWE, a the drive shaft fracture occurs at the point of support on the penetration side.

Experimental testing of the chemical composition and mechanical properties of the material of the shaft and metallographic inspections of the fracture surface by means of electronic and light microscopes carried out in the first part of the paper have shown that there are no significant inhomogeneities and errors in the material of the shaft and that they do not cause damage. Further, the analysis of results referring to the mechanical properties and chemical composition of the repaired shaft at the point of welding, and particularly in the transition zone, shows that they considerably deviate from those prescribed for the material used. Significant inhomogeneity of the material, occurrence of cracks as well as the difference in the microstructure appear in this zone, which is the cause of shaft damage.

The second part of the paper presents the FEM analysis of effects of the cantilever type of support of the planetary gearbox and stress concentration at the point of support due to inadequate finishing, which caused the occurrence of an initial crack. The user unsuccessfully tried to eliminate this weakness by repair welding of the shaft.

Highlights

► The cause of the drive shaft fracture of the BWE SchRs630/6×25 was examined. ► The shaft fracture did not occur due to any errors in the material. ► The cause of the initial crack is inadequate machining of the shaft. ► The cause of the shaft fracture is the badly performed repair welding process.