Abstract
Ceramics have the properties of high-stiffness, proof-corrosion, and light-weight superior to metal materials and so have been applied to a ball and a race in high performance ball bearing and etc. As a recent expansion of this application, a ceramics ball has been applied to the backflow valve, which is comprised in automotive fuel supply system. However, it must be considered sufficiently that ceramic balls can maintain a high confidence over long-term without being broken by cyclic contact loadings, which are generated between a ceramic ball and housing on switching a backflow valve. In this investigation, the stress analysis by FEM was conducted for clarifying failure mechanism due to cyclic contact stress. As results of analysis, the place of highest contact stress was seen directly underneath the contact region between a ball and housing. In ceramics of brittle material, the fracture occurs usually from a microscopic latent flaw in materials. Therefore, it was probabilistically clarified from a view-point of fracture mechanics that a latent internal microscopic flaw was a starting point of fracture.
