1, tooth surface wear
For open gear transmission or closed gear drive containing unclean lubricating oil, some hard abrasive grains enter the friction surface due to the relative sliding between mesh surfaces, so that the profile changes and the backlash increases, so that the gear is too thin to cause tooth breakage. In general, only when the abrasive particles are mixed in the lubricating oil, the abrasive wear of the tooth surface will be caused in the operation.
2, the gluing of the tooth surface
For the high speed and heavy load gear transmission, because of the large friction between teeth, the relative velocity, the meshing temperature is too high, once the bad lubrication, the oil film between the tooth surface will disappear, making direct contact with the metal surface of two teeth, which are bonded to each other. When the two tooth surface to relative movement, hard tooth surface will be part of the material is soft on the tooth surface along the sliding direction and the formation of tore grooves.
3. Fatigue pitting
When contacting two meshing gears, the contact force between the tooth surface and the reaction force causes contact stress on the two working surface. Because the position of the meshing point is changed, and the gear does periodic motion, the contact stress changes according to the pulsating cycle. In such a long time alternating tooth surface contact stress on the tooth surface, the marks will appear small cracks, with the passage of time, the cracks in the surface gradually and the lateral extension of crack to form a ring, so that the tooth surface of small area in the formation of some shallow fatigue spalling.
4, gear broken
The loading gear in the operation of the project, as the cantilever beam, the root by the fatigue limit of the periodic pulse stress exceeds the gear material, will produce cracks in the roots, and gradually expanded, the remaining part is unable to withstand the transmission load occurs when the broken teeth phenomenon. Gear breakage can also be caused by serious impact, partial load and uneven material in the gear.
5, teeth plastic deformation
Under the impact load or heavy load, the tooth surface easily produces the local plastic deformation, thus making the involute tooth profile surface deformation.
