Failure forms of gears:
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 hard abrasive particles enter the friction surface, thereby changing the tooth profile. , the backlash increases, so that the excessive thinning of the gear causes the teeth to break.Under normal circumstances, only when the lubricating oil is mixed with abrasive particles will the wear of the tooth surface abrasive particles be caused during operation.
2. Tooth surface gluing: For high-speed and heavy-load gear transmission, due to the large friction between the tooth surfaces and the high relative speed, the temperature in the meshing area is too high. Once the lubrication conditions are poor, the oil film between the tooth surfaces will disappear. The metal surfaces of the two gear teeth are in direct contact, so that mutual bonding occurs.When the two tooth surfaces continue to move relative to each other, the harder tooth surface will tear off part of the material on the softer tooth surface along the sliding direction to form grooves.
3. Fatigue pitting corrosion: When the two gear teeth meshing with each other are in contact, the acting 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 is done periodically movement, so the contact stress changes according to the pulsating cycle.Under the action of this alternating contact stress on the tooth surface for a long time, small cracks will appear at the tool marks of the tooth surface. As time goes on, the cracks gradually expand laterally on the surface layer. The surface of the tooth produces a small area of spalling and some fatigue craters are formed.
4. Broken gear teeth: gears under load in operation engineering are like cantilever beams. When the periodic stress of the pulses at the root exceeds the fatigue limit of the gear material, cracks will occur at the root and gradually expand. When the remaining part cannot withstand Broken teeth will occur when a load is transmitted.Gears may also break teeth due to severe impact, eccentric load and uneven material during work.
5. Plastic deformation of the tooth surface: Under the impact load or heavy load, the tooth surface is prone to local plastic deformation, so that the curved surface of the involute tooth profile is deformed.