The cap has cyclic symmetry, so only the portion
shown needs to be modeled. The outer diameter of the model is restrained in all
directions to simulate the cap sealed on the bottle top. The near side surface
is restrained normal to the surface cut rather than specifying a rigid contact
surface, thereby reducing the amount of contact checking needed for the
solution. The outer 80% of the opposite side surface was also restrained normal
to the surface. The remaining inner 20% of the opposite side surface was
constrained by a rigid contact surface with touching only and no separation
force specified. Therefore, a "slit" was modeled in the rubber at the center.
This portion of the surface would move along the rigid surface and was permitted
to lift off of the surface at a non-transient pressure application. The lower
(inner) surface was subjected to a pressure load which would follow the inner
surface. This simulates the bottle being squeezed and the fluid pushing against
the bottle cap. The material model used for this analysis was Ogden. The
animation plot will show the cap maintaining contact with the two symmetry
planes until the inner "slit" region rotates off of the inner symmetry plane.
When a full model is viewed, the deflection of the rubber forms a square hole in
the cap.
The following video shows results from the analysis.
Video of Sports Bottle Cap Analysis
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