Assessment Based on Tooth Surface Appearance and Wear Extent
- Excessive Wear: Replacement is required if the wear on the fixed-chord tooth thickness exceeds 60% for the main transmission gear or 10% for the auxiliary transmission gear.
- Excessive Pitting: Replacement is mandatory if fatigue pitting covers one-third of the tooth length and half of the tooth height, or if the pitted area exceeds 30% of the effective tooth surface and the depth reaches 10% of the tooth thickness.
- Severe Damage: Immediate replacement is necessary for severe adhesive scuffing or tooth root fractures; however, for gears with a module (m) > 6mm, tooth inlay repair may be attempted if functionality is not compromised.
- Broken Teeth/Cracks: Immediate replacement is required if damage extends across four or more consecutive teeth or if there are through-cracks at the tooth root, as repair is not viable.
Assessment Based on Abnormal Operational Status
- Abnormal Noise and Vibration: Continuous sharp metallic friction sounds or "clicking" impact noises during operation, combined with an RMS vibration velocity exceeding 4.5 mm/s and noise levels ≥ 85 dB(A), indicate severe gear meshing failure.
- Degraded Transmission Performance: Symptoms include noticeable stuttering, frequent gear disengagement, excessive backlash, significantly reduced load-bearing capacity, and unstable torque transmission.
- Abnormal Oil Temperature: Rapid, abnormal rise in gearbox oil temperature, presence of significant metal wear particles in the lubricant, and oil turning black with excessive impurity content.
