1. Tooth surface wear
For open gear transmission or closed gear transmission containing unclean lubricating oil, due to the relative sliding between the meshing tooth surfaces, some harder abrasive grains enter the friction surface, so that the tooth profile changes and the backlash increases, so that the gear is overly thinned and the tooth is broken. In general, only when abrasive particles are included in the lubricating oil will it cause tooth surface abrasive wear during operation.
2. Tooth surface gluing
For high-speed and heavy-duty gear transmission, due to the large friction between the tooth surfaces and the large relative speed, the temperature of the meshing area is too high, once the lubrication conditions are poor, the oil film between the tooth surfaces will disappear, so that the metal surfaces of the two gear teeth are in direct contact, resulting in mutual bonding. When the two tooth surfaces continue to move relative to each other, the harder tooth surface tears off part of the material on the softer tooth surface in the sliding direction to form grooves.
3. Fatigue pitting
When the two teeth of meshing with each other are in contact, the force and reaction force between the tooth surfaces cause contact stress on the two working surfaces, because the position of the meshing point is changed, and the gear does periodic movement, so the contact stress is changed according to the pulsation cycle. Under the action of this alternating contact stress for a long time, small cracks will appear at the knife marks on the tooth surface, and over time, this crack will gradually expand laterally on the surface, and after the cracks form an annular, the surface of the gear teeth will produce a small area of peeling and form some fatigue pits.
4. The gear teeth are broken
When the periodic stress of the root of the gear bearing the load in the operation project, like the cantilever beam, exceeds the fatigue limit of the gear material, cracks will occur at the root and gradually expand, and the tooth breakage phenomenon will occur when the remaining part cannot withstand the transmission load. Gear breakage may also occur due to severe impact, eccentricity and uneven material during operation.
5. Plastic deformation of tooth surface
Under shock load or heavy load, the tooth surface is prone to local plastic deformation, which deforms the surface of the involute tooth profile.
