In the paint shop lines of an automotive plant, vehicles are moved around suspended by a vehicle-supporting mechanism composed of frontal and rear load-bars. Furthermore, the frontal load-bar is used as an electrical contact point for energy conduction, whereas the rear load-bar is electrically insulated. The frontal load-bar is one of the components that often fail in service causing production line shutdown. This article presents a case study of a fractured load-bar. Material and fracture surface were characterized by magnetic particle inspection, optical microscopy, scanning electron microscopy, hardness and chemical analysis. Results showed that, although the material was according to the project specification, component failures were due to thermal fatigue promoted by the Joule thermal effect, resulting from energy dissipation on the load-bar inner surface, which contacts the vehicle-supporting mechanism. Next to the deformed zone, where heat affected material was detected, the microstructure was changed. These changes are considered to be due to temperatures as high as austenitizing tmeperatures. Temperature estimates performed in order to assess the peak temperature lead to values as high as 1270 deg C. The fracture surface shows the presence of beach marks suggesting that failure has occurred by fatigue.
Failure analysis of frontal load-bar equipment
Engineering Failure Analysis ; 12 , 2 ; 317-324
2005
8 Seiten, 12 Bilder, 1 Tabelle
Aufsatz (Zeitschrift)
Englisch
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