The phenomenon that gear is damaged for some reason during its work, causing it to lose its normal working ability is called failure. There are many types of gear failures. If adopt good material for gears of the geared motor, it will reducer some gear failures. Common forms and causes of failure are:
1, Tooth surface wear
During the transmission of the gear, there is relative sliding between the engaging tooth surfaces. When the gear is under stress, the relative sliding between the tooth surfaces causes the tooth surface to become worn. Wear will destroy the shape of the tooth surface, resulting in unstable transmission; in addition, the wear causes the gear teeth to become thinner, resulting in an increase in the tooth side clearance and a decrease in the tooth hardness.
2, Broken gears
During the meshing process, the bending torque at the root of the gear is alternated. Therefore, the fatigue crack is most likely to occur at this point and the gear teeth are broken. The failure mode of the gear teeth is called the gear tooth fatigue failure. Another break of the gear is a sudden break when it is overloaded for a long time or subjected to an excessive impact load, called an overload failure.
3, Tooth plastic deformation
Under low-speed and heavy-duty working conditions, the tooth surface of the gear is subjected to a large amount of pressure and friction. Due to these forces, the local tooth surface of the softer gear may produce plastic flow, causing groove or convexity on the tooth surface, thereby destroying the tooth profile of the gear and weakening the working ability of the gear. This form of failure of the gear is referred to as plastic deformation of the gear teeth.
4, Pitting in gear surfaces
When the meshing surface is repeatedly subjected to contact pressing and the pressure generated thereby is too large or the use time is too long, the tooth surface generates minute fatigue cracks. As the gear continues to work, the crack will continue to expand along the surface, causing small pieces of metal to peel off the tooth surface, forming pittings and spots. This form of failure that occurs on the tooth surface is called gear pitting. It mostly occurs in closed-gear transmissions with good lubrication conditions.
5, Tooth surface glue
In the high-speed heavy-duty closed-gear transmission, the tooth surface lubrication is more difficult, and the meshing surface generates a local high temperature under the heavy load to bond them together. When the gear continues to move, it will be torn on the softer tooth surface. The tear of the groove is caused by part of the metal material. The failure due to the bonding and tearing of the gear tooth surface is called gear tooth surface glue. It is highly prone to occur in closed worm drives.
