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Spindles are among the key parts of rotatory machinery and featured widely in a variety of industrial equipment. Fracture failure of a spindle (caused either by inappropriate design or operation) could lead to significant economic losses or high numbers of casualties. Using data from accidents, caused by spindle fracture in centrifuges in China as an example, this research work systematically investigates the reasons leading to the fracture failure of the spindles in operation. Our methods include analysing the chemical composition, micro-morphology, and mechanical properties of the fractures. Our results show that the spindle failure is due to a form of fatigue fracturing caused by stress concentration and alternative bending stress. A finite element method was additionally utilised to further calculate and analyse the stress distribution over a spindle. It was discovered that the stress is severely concentrated at the transition fillet of the spindle. Finally, we show that the stress distribution in the spindle can be improved by adopting a structure in the form of a conic section and by reducing the eccentric moment. In this way, the fatigue resistance of a spindle can be enhanced. [ABSTRACT FROM AUTHOR]

Abstract: Zinc oxide whiskers (ZnOw) reinforced lead zirconate titanate (PZT) piezoelectric composites with high strength and high toughness were fabricated by nonpressure sintering at 1100°C. Addition of ZnOw is effective for sinterability and densification of the composites. Incorporating ZnOw to PZT ceramics contributes to an obvious improvement of the fracture properties. The fracture strength and fracture toughness of the composites incorporating 2wt.% ZnOw, compared with the monolithic PZT, are enhanced 46% and 47%, respectively. Improvement of fracture strength is ascribed to the enhancement of the elastic modulus and fracture toughness. Enhancement of fracture toughness is associated with the existence of the observed several mechanisms including crack deflection, whisker bridging, whisker pull-out and rupture due to the intergranular and intragranular whiskers. [Copyright &y& Elsevier]