A bending analysis is performed on an implantable lead model. The structure consists of a five-filar metal coil (linear elastic) inside a polymer tube casing (hyperelastic). The tube is 3.45 mm long with an outer radius of 0.43 mm and an inner radius of 0.36 mm. The wire of the coil has a 0.05 mm radius with an initial 0.0125 mm gap between the filars.
Two contact pairs are defined in each model: one self-contact pair for the coil's filar-to-filar contact, and one contact pair between the coil and the tube. To apply the bending boundary condition, one end of the tube and coil is fixed, and the other end is rotated about the Y axis by 1.2 radians.
Three different models are created:
Solid Tube and Solid Coil
Solid Tube and Beam Coil
Beam Tube and Beam Coil
Figure 51.1: 3-D Models of a Five-Filar Metal Coil Inside a Polymer Tube shows the schematic model representation for the three cases. The specific element types and contact models used are as follows:
| Case Number | Tube Element | Coil Element | Self Contact (between filars) | Tube/Coil Contact | Comments |
| 1 | SOLID186 | SOLID186 | Surface-to-surface | Surface-to-surface | More accurate, but computationally expensive |
| 2 | SOLID186 | BEAM189 | Beam-to-beam | Beam-to-surface | |
| 3 | PIPE289 | BEAM189 | Beam-to-beam | Internal beam-to-beam |
