A multipoint constraint (MPC), force-distributed constraint is applied to the proximal and distal surfaces of the artery by specifying KEYOPT (2) = 2, KEYOPT(4) = 1 and KEYOPT(12) = 5 for the CONTA174 elements, as shown in the following figure:

Figure 25.6: Artery Boundary Conditions

MPC pilot nodes (TARGE170) are fixed in all six degrees of freedom. The boundary conditions allow for radial arterial expansion, while adequately preventing rigid body motion of the artery.

As with the artery, an MPC-based, force-distributed constraint is applied to selected nodes on the proximal and distal ends of the stent (CONTA175), as shown in this figure:

Figure 25.7: Stent Boundary Conditions

MPC pilot nodes (TARGE170) are fixed in all six degrees of freedom.

Surface pressure loads are applied to all nodes on the inner plaque wall, representing the balloon expansion pressure in the first load step (0.1 N/mm²) and blood pressure in the fourth load step (0.0133 N/mm²).

The following figure illustrates the load surface and load history:

Figure 25.8: Uniform Pressure Loading on the Inner Plaque Wall (a) and Load History (b)

(a)	(b)