1. Oil Starvation Symptoms
- Bearing Degradation
- Inner diameter wear (measurable via caliper)
- Outer diameter scuffing & deformation (OD enlargement >5% warrants replacement)
- Thrust bearing discoloration (blue tint indicates >300°C exposure)
- Shaft Failure Modes
- Fracture at turbine journal (stress concentration point)
- Surface cracks from cyclic hardening (visible under 10x magnification)
2. Metallurgical Evidence
| Feature | Technical Interpretation |
|---|---|
| Copper transfer to shaft | Bearing material adhesion due to boundary lubrication |
| Blue/discolored shaft | Peak temperature exposure (200°C=light blue, 400°C=purple) |
| Fatigue fracture patterns | Progressive cracks from imbalance forces (>10% out-of-roundness) |
3. Failure Mechanism
- Thermal Overload
Discoloration correlates with oil film breakdown temperature thresholds:- 200°C+: Synthetic oil oxidation begins
- 300°C+: Bearing material diffusion occurs
- 400°C+: Shaft metallurgical changes irreversible
- Mechanical Stress
Journal cracks propagate from:- Oil feed line blockages (≥90% restriction)
- Extended oil change intervals (>50% beyond OEM spec)
Note: All measurements require comparison with OEM tolerances for accurate diagnosis.
