Bearing Failure RCA: Cracks

 

When a rolling bearing is damaged during machine operation, the entire machine or equipment can seize or malfunction. Since bearings that fail prematurely or unexpectedly cause trouble, it is important to be able to identify and predict failure beforehand, so that preventive measures can be adopted.

Damage Condition

Cracks in the raceway ring and rolling elements. Continued use under this condition leads to larger Cracks or Fractures.

Possible Causes

  • Excessive interference
  • Excessive load, shock load
  • Progression of Flaking
  • Heat generation and Fretting caused by contact between mounting parts and raceway ring
  • Heat generation due to Creep
  • Poor taper angle of tapered shaft
  • Poor cylindricality of shaft
  • Interference with bearing chamfer due to a large shaft corner radius

Countermeasures

  • Correct the interference
  • Check the load conditions
  • Improve the mounting method
  • Use an appropriate shaft shape

 

Cracks 1

Part: Outer ring of a double-row cylindrical roller bearing
Symptom: Thermal cracks occur on the outer ring side face
Cause: Abnormal heat generation due to contact sliding

 

Cracks 2

Part: Roller of a tapered roller thrust bearing
Symptom: Thermal cracks occur at large end face of roller
Cause: Heat generation due to sliding with the inner ring rib under poor lubrication

 

Cracks 3

Part: Outer ring of a double-row cylindrical roller bearing
Symptoms: Cracks propagated outward in the axial and circumferential directions from the Flaking origin on the raceway surface
Cause: Flaking from a flaw due to shock

 

Cracks 4

Part: Outer ring of a double-row cylindrical roller bearing used for outer ring rolling (Outer ring rotation)
Symptom: Cracks on outside surface
Cause: Flat Wear and heat generation due to non-rotation of the outer ring

 

Cracks 5

Part: Raceway surface of outer ring of damage “Cracks 4”
Symptom: Outside surface crack propagating to the raceway

 

Cracks 6

Part: Inner ring of a spherical roller bearing
Symptom: Axial Cracks on raceway surface
Cause: Large fitting stress due to temperature difference between shaft and inner ring

 

Cracks 7

Part: Cross section of cracked inner ring of damage “Cracks 6”
Symptom: Origin is directly beneath the raceway surface

 

Cracks 8

Part: Roller of a spherical roller bearing
Symptom: Axial Cracks on rolling surface

 

Source: NSK