1. Tooth Surface Damage
Tooth Surface Wear
is categorized into abrasive wear and adhesive wear. Abrasive wear is often caused by contaminated lubricants, metal debris, or external dust, leading to uniform or localized material spalling on the tooth surface. Adhesive wear, also known as galling, frequently occurs under high-speed, heavy-load conditions. Excessive localized temperatures cause the metal surface layer to adhere, forming scratches when relative motion occurs. Severe cases may result in tooth surface adhesion.
Tooth Surface Pitting
This contact fatigue damage involves microcracks forming in the surface layer under alternating contact stresses. As cracks propagate, metal particles detach, creating pitted depressions. Initial pitting typically occurs on root surfaces before spreading across the entire tooth face, degrading transmission accuracy and generating noise.
Plastic Deformation of Tooth Surfaces
Common in soft-toothed gear shafts or overloaded conditions, where stress exceeds the yield limit causing plastic flow. This results in plastic sharpening of tooth tips, plastic collapse at tooth roots, or wave-like deformation along the sliding direction, compromising tooth profile accuracy.
2. Tooth Body Damage
Tooth Root Fracture
The tooth root is a critical stress concentration zone on gear shafts. Under alternating loads, impact loads, or severe overload, fatigue cracks may form at the root. These cracks propagate, ultimately causing tooth breakage. Tooth breakage is categorized into fatigue fracture and overload fracture: the former exhibits distinct fatigue arc patterns on the fracture surface, while the latter shows a rough fracture surface without fatigue characteristics.
Tooth Surface Spalling
A more severe form of contact fatigue damage than pitting, where large areas of tooth surface metal flake off in sheet-like fragments, forming deep pits. This is often caused by internal defects in the shaft material, improper heat treatment, or prolonged exposure to excessively high contact stresses.
3. Shaft Body Damage
Shaft Neck Wear
Prolonged friction at the shaft neck-bearing interface, inadequate lubrication, or excessive assembly clearance can reduce shaft neck dimensions and increase surface roughness. This impairs bearing operation and may cause shaft neck-bearing seizure in severe cases.
Shaft Body Bending Deformation
Excessive bending moments, significant installation misalignment, or prolonged operation in high-temperature environments can cause plastic bending of the shaft body. This results in uneven gear meshing clearance, accelerating tooth surface wear and vibration.
Shaft Body Cracks and Fractures
Stress-concentration zones like keyways and shoulders are prone to fatigue cracks under alternating torque and bending moments. If undetected, crack propagation can cause shaft fracture—a severe mechanical failure.
4. Other Damages
Corrosion Damage
Operating in humid environments, exposure to corrosive media, or lubricant oxidation producing acidic substances can cause rust and pitting corrosion on gear surfaces and shaft bodies, degrading mechanical properties.
Keyway Damage
The mating surfaces of keyways and keys endure prolonged torque loads, leading to keyway wear, deformation, or cracking. This compromises the circumferential fixation between gears and shafts, impairing power transmission.