Failure analysis of the end eye connection of the bucket wheel excavator portal tie-rod support

This paper describes the failure analysis results of the bucket wheel excavator (BWE) portal tie-rod support. The results of finite elements analysis (FEA) point out the occurrence of pronounced stress concentration, whereby multiple stresses in the failure zone exceed the yield stress of the basic material. Experimental investigation on fracture surfaces by scanning electron microscope (SEM) and light microscope (LM) revealed the existence of porosities and inclusions in the weld metal. Moreover, various types of fracture (fatigue, transition, brittle) and their uneven fraction observed on fracture surfaces are induced by structural characteristics of the base metal, welding technology and the construction itself. Based on the presented results it is conclusive that the failure of the support was the consequence of superposition of the negative effects caused by inadequate shaping and dimensioning of the support assembly for given load conditions, as well as influences of mentioned defects of the metal weld structure. (C) 2008 Elsevier Ltd. All rights reserved.