Retrievals obtained after revision surgery, provide valuable information on the rate of wear and the causes of wear that take place in vivo. The aim of this study was to perform a root cause failure analysis to determine the principle reason for mechanical failure on failed acetabular cups, retrieved during revision surgery, by making use of sound engineering failure analysis techniques. The bearing couples varied between steel on UHMWPE and ceramic on UHMWPE. The information gained during this analysis brought to the four that the principle mode of mechanical failure for acetabular cups is overheating of the UHMWPE. The resulting overheating is mainly due to a lack of good and/or sufficient lubrication.
A large number of diesel engine failures have been reported in the immediate past. The large proportion of these engines that were investigated, were recently overhauled engines that failed soon after the overhaul process. In some cases, these engines failed on the dynamometer, while it was tested before delivery to the customer. The most common failure on a large number of these engines, were pistons seizing in the crown region causing seizure of the piston in the cylinder. Tests were done to correlate the lubricity of the fuel that was used and the failure of the engines. Limits were obtained from which it could be determined when the fuel was not of a proper quality and where engine failures took place. It is finally recommended that the specification SABS 342 be amended to include the requirements for the lubricity of diesel fuels.
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