Appendix 1: FEA supplementary information
1. Element Type
Stent: C3D8R - 8 noded linear brick element, reduced integration
Thin sheet: S4R - 4 noded doubly curved thin shell
2. Boundary conditions (BC)
Radial Strength (Fig 1):
Stent
Single nodes are selected and following displacement type BC's are applied:
U1 = U2 = U3 = UR1 = UR2 = UR3 = 0 on a cylindrical coordinate system.
Cylinder
The whole cylinder is selected and following displacement type BC's are applied:
U1 = -1, U2 = U3 = UR1 = UR2 = UR3 = 0 on a cylindrical coordinate system.
Fig 1 Boundary conditions on the stent and thin sheet during radial strength test.
Flexibility (Fig 2)
Boundary conditions for the flexibilty test are applied on two reference nodes. These nodes are
created in the centre of each end. One reference node is fixed in all directions:
U1 = U2 = U3 = UR1 = UR2 = UR3 = 0
The other boundary condition on the opposite reference node dictated the degree of bending:
UR2 = 1
Appendix 1: FEA supplementary information
Fig 2 Boundary conditions on the stent during flexibility test.
Longitudinal resistance (Fig 3)
Similar to the flexibility test, one reference point is fixed in all directions:
U1 = U2 = U3 = UR1 = UR2 = UR3 = 0
The other reference point is displacement controlled along the longitudinal axes:
U3 = 0.1, U1 = U2 = UR1 = UR2 = UR3 = 0
Fig 3 Boundary conditions on the stent during longitudinal resistance test.
Material Model input:
Input parameters
A [𝒔−𝟏 ]
0.0005
B [𝑴𝑷𝒂−𝟏 ]
n
𝒓𝟏
𝝀𝒎
µ [𝑴𝑷𝒂]
K [𝑴𝑷𝒂−𝟏 ]
N
0.85
0.15
0.98
0.7
0.19
0.00067
1
Table 1 Values of the non-linear viscoelastic model parameters determined from fitting to PLLA tensile test data.
Appendix 1: FEA supplementary information
Abaqus input file material model description
** MATERIALS
**
*Material, name=Parallel Network
*Hyperelastic, arruda-boyce
0.19,0.51,0.00067
*VISCOELASTIC, NONLINEAR, NETWORKID=1, SRATIO=0.98, LAW=HYPERB
0.0005, 0.85,
**
0.15