A miniature flexible joint using silicone rubber elastomer and wrapped insulating boot was designed. The relation between effective and geometric pivot points was studied. The quadrinomial second order Mooney-Rivlin invariant model was used to describe the constitutive relationship of the elastomer. The excursions of effective and geometric pivot points of flexible joint at different vector angles under 0MPa and 9MPa vessel pressure were calculated respectively using ANSYS. Both effective and geometric pivot point cylinders were obtained. The simulation and experiment results of effective pivot point were compared. The accuracy of the geometric pivot point excursion was verified by the experiment of clearance crash. In addition

the reason of the effective pivot point excursion was also studied. Results show that the simulated effective pivot point cylinder has a good agreement with the experiment. The effective and geometric pivot points are of different concepts. The effective pivot point excursion is limited to a radius of 2.5mm

1.4mm high cylindrical envelope while the geometric pivot point excursion is limited to a radius of 0.013mm

0.6mm high cylindrical envelope. The effective pivot point excursion is caused by different strains of each reinforcement and elastemer.