Rotary bending fatigue testing of over 600 MP35N and DFT conductor samples showed comparable S-N fatigue data sets, with failures initiating on the outside surface of the wire.
MP35N and DFT conductors used in cardiac leads show similar fatigue characteristics in rotary bending tests, with failures initiating on the outside surface.
Implantable electrical conductor wires and coils of MP35N and drawn MP35N tube filled with a silver core (DFT) were tested in rotary bending to evaluate fatigue characteristics and failure mechanisms. Detailed stress analysis enabled evaluation of helical coil fatigue in bending with respect to theoretical stress. The relations between the maximum cyclic stress (S) and the cycles to failure (N) were obtained by introducing cyclic stresses on over 600 samples. Microscopic evaluation using scanning electron microscopy was performed to identify failure mechanisms. The results show that the stress analysis presented is a viable means for assessing the stress state in a composite coil structure in rotary loop testing, comparable S-N fatigue data sets for MP35N and DFT conductors are not consistently significantly different, S-N relationships for coils and wires of the MP35N and DFT appear to lie on the same curves, and failures of all sample types initiate on the outside surface of the wire. Differences in crack propagation and final fracture are shown as a function of sample type and cyclic stress.
Altman et al. (Thu,) conducted a other in Cardiac lead design (materials testing) (n=600). Rotary bending fatigue testing was evaluated on Fatigue characteristics and failure mechanisms (relations between maximum cyclic stress and cycles to failure). Rotary bending fatigue testing of over 600 MP35N and DFT conductor samples showed comparable S-N fatigue data sets, with failures initiating on the outside surface of the wire.