PSI - Issue 4

Zoran Odanovic / Procedia Structural Integrity 4 (2017) 56–63

63

Author name / Structural Integrity Procedia 00 (2017) 000 – 000

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4. Conclusion

Based on the investigation results, the following can be concluded. The chemical composition analysis indicate that the steel used for the fractured axle is in accordance with the standard requirements. Mechanical properties of applied material are below the requirements defined in standard EN 13261:2010. Low values of the strain fracture toughness K Ic , especially in transverse direction, indicate low resistivity to the propagation of the initiated cracks from the axle surface. Low values of the tested mechanical properties could be explained as a result of the inadequate reduction rate in hot rolling/forging process during the axle production, or inadequate heat treatment process after hot working. It can be concluded that corrosion was initiated from the damaged axle coat, and from below the coat to the whole surface of the critical radius thus creating conditions for pit formation. Crack initials are caused by corrosion pits at the surface of the critical radius of the axle. Due to the weakness of the material, these cracks propagated, forming tooth-like cracks and spreading by fatigue mechanism, until the axle could not withstand the stresses arising from exploitation conditions. These circumstances lead to the final fracture of the axle. In order to prevent similar failures in the future, it is necessary to improve the control of the corrosion protection and the inspection of the axle from the aspect of the initial cracks during the regular maintenance.

Acknowledgements

The author wish to express gratitude to Serbian Ministry of Education, Science and Technology development, for supporting this paper through Projects TR 35002 and ON 172005.

References

Zerbst, U., Beretta, S., Kohler, G., Lawton, A., et al., 2013. Safe life and damage tolerance aspects of railway axles - A review. Engineering Fracture Mechanics 98, 214-71 Meral, B., Necati, T., Rahmi, G., 2010. Realibility and fatigue life evaluationof railway axles, Journal of Mechanical Science and Technology, 24(3), 671-679. Torabi, A.,R., Heidary, K., M., 2012. Fatigue Crack Growth in a Solid Circular Shaft under Fully Reversed Rotating Bending, J. Fail. Anal. and Preven;12, 419-426 Beretta, S., Conte, L., A., Rudin, J., 2015. From atmospheric corrosive attack to crack propagation for A1N railway axles steel under fatigue, Eng. Failure analysis, 47, 252-264. Odanovic, Z., Ristivojevic, M., Milosevic-Mitic, V., 2015, Investigation into the causes of fracture in railway freight car axle, Eng. Failure analysis, 55, 169-181. Odanovic, Z., 2011. Testing report Nb. 421116-168. Belgrade, pp. 1-16. http://toscelikniksic.me/supplier/manufacturer/carbon/special/alloy/products/mills/grade/standard/C45.html], 2016. William, M., 1973. Plane strain fracture toughness (KIc), Data handbook for metals, Army materials and mechanics research center, AD-773 673, pp. 38 Tauscher, S., 1981. The correlation of fracture toughness with charpy v-notch impact test data, Technical report ARLCB-TR-81012, pp. 10 Standard SRPS EN 13261:2009+A1:2010, Institute for Standardization of Serbia, http://www.iss.rs Standard SRPS P.F2.310:1968, Institute for Standardization of Serbia, http://www.iss.rs Schumann, H., 1989. Metalografija, TMF, Beograd, 225-230.