Gear damage can manifest in various forms including gear tooth breakage, tooth surface wear, tooth surface pitting, tooth surface scuffing, and plastic deformation of gear teeth. The details are as follows: 1. Tooth surface wear: During gear transmission, relative sliding occurs between the meshing surfaces of gear teeth. Under load, this relative sliding causes wear on the tooth surface. Wear can distort the tooth profile, leading to unstable transmission. Additionally, wear thins the gear teeth, increasing backlash and reducing tooth strength. Tooth surface wear is the primary failure mode for open gear transmissions (exposed gear transmissions) with poor lubrication conditions, as well as for open worm drives. 2. Tooth surface pitting: During gear operation, when the meshing surfaces are repeatedly subjected to contact pressure, and the resulting stress is excessive or prolonged, microscopic fatigue cracks develop on the tooth surface. With continuous operation, these cracks expand along the surface, causing small pieces of metal to flake off, forming pits and craters. This type of failure is called tooth surface pitting. Severe pitting can damage the working surface of the gear teeth, causing unstable transmission, noise, and even rendering the gear inoperable. 3. Tooth surface scuffing: In high-speed, heavy-duty enclosed gear transmissions, lubrication of the tooth surfaces is challenging. Under heavy loads, localized high temperatures can cause the meshing surfaces to weld together. As the gear continues to move, it may tear off portions of the softer tooth surface, creating grooves. This failure, caused by surface welding and tearing, is known as tooth surface scuffing. Once scuffing occurs, the tooth surface is severely damaged, leading to gear failure. This type of failure is particularly common in enclosed worm drives. 4. Plastic deformation of gear teeth: Under low-speed, heavy-duty conditions, the tooth surfaces of gears are subjected to significant pressure and friction. These forces can cause localized plastic flow in the softer material, resulting in grooves or raised ridges on the tooth surface. This distorts the tooth profile and renders the gear inoperable. This failure mode is called plastic deformation of gear teeth. 5. Gear tooth breakage: During operation, gear teeth experience forces similar to a cantilever beam, with the highest bending moment and stress concentration at the root of the tooth. During meshing, the bending moment at the root alternates, making it the most susceptible location for fatigue cracks, which can lead to tooth breakage. This failure mode is called fatigue breakage. Another form of breakage occurs due to prolonged overload or sudden excessive impact loads, known as overload breakage.
