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The inspection of a failed crankshaft of a can-manufacturing production line was conducted by One Eighty Materials Engineering in response to a request for us being contracted to establish the root cause of the failure. The crankshaft belonged to one of the sub-assemblies in the can-manufacturing production line of a metal packaging company. The investigation aimed to determine the failure mechanism and its effects on the surrounding equipment components to assess the implications for an insurance claim.

Non repairable fracture through thickness of crankshaft
Overview of crankshaft
Overview of crankshaft


To gain insights into the failure, a representative of One Eighty Materials Engineering visited the metal packaging company. Site visits involved examining the production line operation and inspecting the damaged components, particularly the crankshaft, bull gear, and pinion gear. Visual observations and measurements were made to understand the nature and extent of the failure.

Failed crankshaft investigation
Striations of the fracture surface on the bull gear side also appear to originate from the shoulder of the crankshaft.


The inspection revealed the following key findings:

  1. The crankshaft failure was attributed to bending fatigue near the shoulder, with the fracture running through the entire diameter of the shaft. The 0.5 mm radius at the shoulder acted as a stress concentrator, exacerbating the issue.
  2. The damage to the bull and pinion gears was found to be a consequence of the crankshaft failure. Heat damage and scratches were observed on these gears, indicating misalignment as a result of the crankshaft failure.
  3. The replacement drive shaft showed evidence of non-uniform heat damage and scratches, along with signs of case hardening on the gear teeth, likely to enhance durability.
Replacement drive shaft


Based on the inspection, One Eighty Materials Engineering concluded that the crankshaft failure resulted from bending fatigue near the shoulder. However, the precise root cause necessitated further metallurgical testing. Recommendations were made for an in-depth analysis of the failed components to ascertain the exact cause of the failure. Moreover, the potential risk of similar failures in other production lines with similar equipment was highlighted, stressing the importance of preventive maintenance and thorough risk assessment.

Recommendations for Further Analysis:

  1. Conduct further metallurgical testing on the crankshaft to determine the exact root cause of the failure.
  2. Evaluate the risk of similar failures in other production lines and conduct preventive maintenance to avoid potential future failures.
  3. Perform bending and fatigue life calculations to facilitate predictive maintenance plans and minimise unexpected failures in the future.
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