PSI - Issue 23

Aleksandar Sedmak et al. / Procedia Structural Integrity 23 (2019) 45–50 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The crack length vs. number of cycles, shown in Sedmak et al (2019), indicated that the failure of implant stem will occur after 40 steps of crack growth, since both K I and crack length start to grow in unstable manner. Corresponding number of cycles is cca 80 Million, which approximates twenty years of active person walking pattern. Experience with hip implant failures indicate that its lifespan is cca 15 years. For numerical simulation of crack propagation, criterion of linear elastic fracture mechanics were applied, i.e. unstable crack growth is reached in case when K I reaches K Ic . Applying that, the unstable crack growth will occur after the critical crack length of 18.5 mm, i.e. after 37 th step. The critical crack value obtained numerically (18.5 mm) can be well correlated with a c , determined by simple fracture mechanics analysis, a c =16.2 mm, Sedmak et al (2019). Based on results presented here, one can conclude that fracture and fatigue behavior of implants made of Ti alloys is now well understood and can be analysed successfully with available numerical and experimental methods/tools. More specifically, one can conclude the following:  In the case of static failure, stress-strain analysis can be used for better design to avoid stress concentration.  In the case of crack presence, relatively simple fracture and fatigue analysis, based on FEM and XFEM, provides reliable and realistic results.  In the case of crack propagation under fatigue loading, relatively simple fatigue analysis, based on XFEM, provides also reliable and realistic results.  More advance methodology should include the spectrum of operating loads that occurs in the real case during the walking cycle and more detailed analysis of the stress intensity factors for the Mode II and III values. Tatić, U., Čolić, K., Sedmak, A., Mišković, Z., Petrović , A., 2018. Measuring procedures and evaluation of the stress strain fields on the locking compression plates. Technical Gazette 25, 1, 112-117 T atić, U., 2017. Analysis of the influence of geometry and biomaterial on orthopedic reconstructive plate integrity and life (in Serbian) doctoral thesis, University of Belgrade Legweel K., Sedmak A., Čolić K. , Burzić Z. , Gubeljak L., 2015. Elastic-Plastic Fracture Behaviour of Multiphase Alloy MP35N. Structural Integrity and Life, 15, 163-166. Sedmak A., Čolić K. , Burzić Z. , Tadić S , 2010. Structural Integrity Assessment of Hip Implant Made of Cobalt-Chromium Multiphase Alloy. Structural Integrity and Life, 10, 161-164. Sedmak A., Milošević M. , Mitrović N. , Petrović A. , Maneski T., 2012. Digital Image Correlation in Experimental Mechanical Analysis. Structural Integrity and Life, 12, 39-42 Paliwal, M., Allan, D.G., Filip, P., 2010. Failure analysis of three uncemented titanium-alloy modular total hip stems. Engineering Failure Analysis, 17, 1230 – 1238. Chao J.; Lopez V., 2017. Failure analysis of a Ti6Al4V cementless HIP prosthesis. Engineering Failure Analysis, 14, 822 – 830. Colic K., Sedmak A., Gubeljak N., Burzic M., Petronic S., 2012. Experimental analysis of fracture behavior of stainless steel used for biomedical applications. Structural Integrity and Life, 12, 59-63. Milovanović, A., Sedmak, A., Čolić, K., Tatić, U., Đorđević, B., 2017. Numerical analysis of stress distribution in total hip replacement implant, Structural Integrity and Life.17, 139 – 144 Jovicic, G., Zivkovic, M., Sedmak, A., Jovicic, N., Milovanovic, D., 2010. Archives of Civil and Mechanical Engineering 10, 19-35 Mitrovic, N., Milosevic, M., Sedmak, A., Petrovic, A., Prokic-Cvetkovic, R., 2011. Application and Mode of Operation of Non-Contact Stereometric Measuring System of Biomaterials. FME Transactions 39, 55-60 Čolić, K., Sedmak, A., Legweel, K., Milošević, M., Mitrovi ć, N., Mišković, Z., Hloch, S., 2017. Experimental and Numerical Research of Mechanical Behaviour of Titanium Alloy Hip Implant, Technical gazette, Vol. 24, 709-713, June 2017; DOI: 10.17559/TV 20160219132016. Sedmak, A., Čolić, A., Grbović, A., Balac, I., Burzić, M., 2019. Numerical Analysis of Fatigue Crack Growth of Hip Implant, Engineering Fracture Mechanics, DOI:10.1016/j.engfracmech.2019.10649. 5. Conclusion 6. Acknowledgment We acknowledge the support for this investigation by the Ministry for Education, Science and Technological Development, project TR35040 and ON174004. We also thank Prof. Dr. Aleksandar Grbovic who provided insight and expertise that greatly assisted the research. References