Metallurgical and Mechanical Failure Analysis of an Aftermarket Flywheel

Authors

DOI:

https://doi.org/10.51501/jotnafe.v37i1.90

Keywords:

Flyhweel failure, Gray cast ion, fissure cracks, porosity, dendrites, manufacturing flaws, forensic engineering, San Diego

Abstract

A failure analysis investigation was performed on the remnants of an aftermarket gray cast iron flywheel that catastrophically fractured during operation in a vehicle after 24 miles of operation. Light microscopy, 3D X-ray micro-computed tomography (micro-CT), scanning electron microscopy (SEM), metallography, and hardness/tensile testing techniques were utilized to characterize manufacturing quality, mode(s) of failure, microstructural variation, fracture surfaces, and mechanical properties of the failed component. Light microscopy examination of the remnant surfaces showed that the flywheel shattered with signs of radial heat checking fissure cracks. A metallurgical examination of the flywheel showed that it was manufactured from cast gray iron, with evidence of microstructural changes near heat-affected zones from graphite flakes in a ferrite/pearlite matrix to needle and lath formations similar to bainite or martensitic phases. The CT scan slices and fracture surface examination in the SEM showed signs of porosity and dendritic formations along a fracture surface believed to be the crack initiation location. The analysis suggests manufacturing flaws found within the flywheel were a likely contributing factor leading to premature failure during service. 

References

D. Dellinger, “Case C: A Cracked Automobile Flywheel Flex Plate,” Failure Analysis of Engineering Materials, pp 483 – 491, 2002.

W. Becker and R Shipley, “Example 1: Cracking in a Gray-Iron Cylinder Head Caused by Microporosity,” in ASM Handbook Volume 11 Failure Analysis and Prevention. ASM International, 2002, pp. 112-113.

E. Unterweiser, “Example 11: Cracking in a Gray-Iron Cylinder Blocks Caused by Casting Stresses,” in ASM Handbook Volume 11 Failure Analysis and Prevention. ASM International, 2002, pp. 134-135.

X. Hou, Y. Li, and T. Jiang, “Fracture Failure Analysis of Ductile Cast Iron Crankshaft in a Vehicle Engine,” Journal of Failure Analysis and Prevention, vol. 11-1 pp. 10-16, 2011.

R. Bossi, J. Cline, E. Costello, and B Knutson, “X-ray Computed Tomography of Castings,” Wright Research and Development Center, Interim Report fr Period April 1989- September 1989.

Downloads

Published

2021-01-08

How to Cite

Kar, N. (2021). Metallurgical and Mechanical Failure Analysis of an Aftermarket Flywheel. Journal of the National Academy of Forensic Engineers, 37(1). https://doi.org/10.51501/jotnafe.v37i1.90

Issue

Section

Articles