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Unformatted text preview: with this risk α is thus known. This determination has been extended to most classic surfaces. Figure 5 presents the uncertainty zones obtained for a cylinder and a sphere. In the next section, this uncertaint y model is used to demonstrate the impact of the geometrical variations on the failure of a mechanism. 230
Cylinder C R J. M. Linares et al. Propagated uncertainty at point Mi R C Sphere
V Nominal feature Figure 5; Case of a cylinder and a sphere 4. INDUSTRIAL CASE STUDY The industrial example of a fuel pump will be used to illustrate the impact of geometrical variations on the operation performance of mechanical systems. In the last years, the injection pressure in diesel engines has greatly increased. Consequently, the internal mechanical loads have become stronger and failures of several injection pumps appeared.
Cam roller Hertz’s critical tension Fuel pump cam Figure 6; Industrial case These failures are quasi instantaneous . They occur during the first running cycles or at low op...
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