What are the failure modes of gears?
3 Answers
Gear failure modes include gear tooth breakage, tooth surface pitting, and tooth surface scuffing. Gear tooth breakage: There are generally two types of gear tooth breakage: one is fatigue breakage caused by repeated bending stress and stress concentration, and the other is overload breakage caused by sudden severe overload or impact load. Tooth surface pitting: During gear operation, under the repeated action of alternating contact stress at the meshing point, small cracks will form on the tooth surface near the pitch line. Tooth surface scuffing: In high-speed and heavy-duty gear transmissions, the pressure between tooth surfaces is high, the temperature rises significantly, and lubrication is poor. When the instantaneous temperature becomes excessively high, local melting and metal adhesion occur between the two tooth surfaces. As the surfaces move relative to each other, the adhered areas are torn apart, resulting in banded or large-area scars along the sliding direction on the tooth surface.
Gear failure is quite common in cars, and I've seen many cases, mainly occurring after prolonged driving with various issues. For example, fatigue fracture refers to gears slowly cracking under repeated stress; pitting means small pits on the surface, often happening when lubrication is insufficient; wear is normal friction loss, but if too severe, the gears become thin; plastic deformation occurs due to excessive load causing bending; and scuffing happens when metals stick together due to poor lubrication. In transmissions, these problems can affect smooth gear shifting. I've found that regular oil changes and checking gear oil levels can prevent most failures, avoiding breakdowns and delays on the road.
I've been driving for over 30 years and have encountered gear failures several times, in various forms. I remember once on the highway when the car suddenly started shaking violently, and the mechanic later said it was pitting, with the gear surface full of pits and dents. Another time, there was a loud abnormal noise during startup, and it turned out to be excessive wear, with the edges completely worn down. I've also experienced plastic deformation, which happened when the gear bent under overload while transporting goods, and the repair cost was quite high. These failures not only affect driving safety but can also shorten the car's lifespan. I recommend everyone to step on the gas lightly, avoid overloading, and get regular maintenance to prevent unnecessary expenses like I had to bear.
