PSI - Issue 2_B

M. Fitzka et al. / Procedia Structural Integrity 2 (2016) 1039–1046 Author name / Structural Integrity Procedia 00 (2016) 000–000

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Figure 4. EDX analysis of the particle at the surface of the specimen shown in Fig. 3(a-b).

4. Conclusion

For the first time, adapting the ultrasonic fatigue testing method to sub-millimeter wires has been accomplished. This novel technique presents the opportunity to rapidly acquire fatigue properties for envisaged in vivo lifetimes for potential product applications, as well as contribute to the development and introduction of new materials. The following conclusions can be drawn from testing low-Ti MP35N wire with 100 µm diameter: 1. Lifetimes measured with the novel technique at 20 kHz cycling frequency show good agreement with conventional servo-hydraulic tension-tension fatigue tests, proving the equivalence of the vastly accelerated testing method. 2. This is the first reported evidence of fatigue tests of low-Ti MP35N wire with 100 µm diameter that was conducted beyond 10 8 cycles. No fatigue limit exists, and failures were found in the regime above 10 8 cycles. 3. In agreement with earlier studies, crack initiation in thin MP35N low-Ti wire is controlled by Al 2 O 3 inclusions at the surface, with typical diameters in the range of a few micrometers. Acknowledgements This work was supported by Medtronic plc., MN, USA, through a grant to the University of Natural Resources and Life Sciences, Vienna. References Altman, P.A., Meagher, J.M., Walsh, D.W., Hoffmann, D.A., 1998. Rotary bending fatigue of coils and wires used in cardiac lead design. J. Biomed. Mater. Res. 43, 21-37. Fallen, C.T., Costello, J., Crawford, G., Schmidt, J.A., 2001. Measuring the elastic properties of fine wire. Journal of Biomedical Materials Research - Applied Biomaterials 58, 694-700. Hildebrand, L.B., Schmidt, J.A., Prentice, J.K., Stotts, L.J., 1999. Quantitative, low cycle, crack initiation fatigue testing of fine wires and CENELEC standard pacing coil. J. Biomed. Mater. Res. 48, 251-257. Ishmaku, A., Han, K., 2001. Characterization of cold-rolled and aged MP35N alloys. Mater. Charact. 47, 139-148. Mayer, H., 2016. Recent developments in ultrasonic fatigue. Fatigue Fract. Eng. M. 39, 3-29.