Advanced Materials & Processing

In the present work, a failed connecting rod from a motorcycle engine was investigated for the root cause of and possible mechanisms leading to its premature failure.  In addition to finding the root cause, the expectation from this study was to possibly improve the existing designs or practices to avoid similar failures in future. These results were validated using a finite element analysis (FEA) simulation. A Scanning Electron Microscope was used for investigating the mechanisms of fracture modes, optical microscopy for studying the microstructures and visual inspection were primarily utilised to determine the root cause of the failure. In conclusion, it was determined that the root cause for the premature failure of the connecting rod was the presence of scale build-up inclusions, which led to micro cracking during fatigue loading of the component. It is most likely that the connecting rod failed on the end of exhaust stroke, due to the tensile force being at its highest, when the piston reaches TDC. This is due to the inertia of the piston, pin, and upper end of the connection rod moving upwards while there are no compressive forces to take them under consideration.

K. Bari, “Characterization of the porosity in TRISO coated fuel particles and its effect on the relative thermal diffusivity,” Nuclear Engineering and Design, vol. 265, pp. 668-674, 2013.

Uddeholm, Temperature guide for tempering steel, 2015.

S. MacKenzie, “Overview of the Mechanisms of Failure in Heat Treated Steel Components,” ASM International Failure Analysis of Heat Treated Steel Components, 2008.

P. Juvonen, “Effects of Non-Metallic Inclusions on Fatigue Properties of Calcium Treated Steels,” 2006.

M. ashby, “www.grantadesign.com,” Cambrige Engineering Selector. [Online]. [Accessed 10 04 2017].

A. Strozzi, A. Baldini, M. Giacopini, E. Bertocchi and S. Mantovani, “A repertoire of failures in connecting rods for internal combustion engines, and indications on traditional and advanced design methods,” Engineering Failure Analysis, vol. 60, 2016.

S. Ishida, Y. Hori, T. Kinoshita and T. Iwamoto, “Development of technique to measure stress on connecting rod during firing operation.,” SAE Technical Paper 951797, pp. 1851-1856, 1995.

R. Celin, B. Arzensek and D. Kmetic, “A Metallographic Examination of a Fractured Connecting Rod,” Institute of Metals and Technology, 2007.