Manufacturing Simulation Using Finite Element - Finite Element Analysis for Satellite Structures - page 271

Fig. 7.3 Clamped boundary conditions

The head material flows tangent to the die surface as it deforms, and this flow
controls not only the rivet head shape but also the expansion profile on the radial
direction and the contraction profile on the rivet axial direction.

The finite element model is described in the following steps:

• The clamping areas are constrained in x, y, and z directions Fig. 7.3 .
• The tail die and the head die are modeled as rigid bodies. Each rigid body has a
reference point through which the impact riveting force is applied. The applied
impact force versus time profile has a triangular shape over a time of 1-6 ms,
which reflects the duration of this process. Regularly, the impact force is applied
once to deform the rivet, but sometimes due to the rivet size and in an effort to
minimize panel damage, the impact force is applied multiple times within a
period of time that may last up to 10 s Fig. 7.4 .
• Symmetry boundary conditions were considered and only a quarter of the small
panel assembly was modeled. Only the symmetry around X-Z plane is shown of
Fig. 7.5 .
• Contacts are defined between all the assembly components (rivet—dies—
panel—stiffener).,

- Finite sliding (penalty formulation) is used to define the contact between the
die and the rivet:
For the Tangential behavior, Penalty formulation is used for friction with
standard coefficient of (0.47—Steel and Aluminum). For the normal behavior,
hard contact is defined with allow separation after contact.