Failure analysis of a car suspension system ball joint

Abstract

1. BackgroundThis study describes the analysis and investigation of the causes of the sudden failure of a MacPherson strut suspensionsystem ball joint. The axis of the ball joint element showed a complete fracture which occurred midway between the top andbottom section changes of the element, as shown in Fig. 1. The failed ball joint element is shown in Fig. 1, along with a balljoint element not previously used, in order to show the height at which the fracture occurred in the element.The aim of this study was to determine whether the failure was caused by defective materials, overload or deficient de-sign of the element.2. Experimental procedureA fractographic inspection of the fractured surface of the element was initially performed using optical microscopy. Afterthis inspection, samples were extracted to analyze the material microstructure and some of the fractographic features bymeans of Scanning Electron Microscopy (SEM). The microstructural analysis was performed in order to obtain informationabout previous thermo-mechanical treatments to the element. Optical Emission Spectroscopy (OES) was used to identify thechemical composition of the failed element. Vickers hardness was also measured on the failed element. It is worth notingthat before any measurement was performed, any traces of grease and debris were removed from the element.2.1. Fractographic studyFig. 2 shows a macroscopic image of the fractured surface of the ball joint obtained by optical microscopy. Three differentcharacteristic zones of the fracture are identified in the figure as zones A–C. Zones A and B indicate opposed zones where the