Pitting, gear

The API, with help from gear manufacturers, has a 1977 standard (API 613) for rating gears. (See Chapter 4.) A common procedure for comparing and sizing gear is based on the tooth pitting index, the K factor... 

AGMA 211.02, Surface Durability (Pitting) of Helical and Herringbone Gear Teeth, Washington, D.C., 1969. 

The types of wear and failure that occur in metallic gears are distinctive and have been subjected to close analysis over many years. The more common types of failure are abrasion, scuffing, pitting, corrosion, plastic yielding and... 

Gear lubricants In addition to the usual oxidation and corrosion inhibitors, lubricants for heavily loaded gears almost always contain EP additives containing sulphur, chlorine or phosphorus. In order to function, these additives must react locally with the metal surfaces, and yet the extent of the reaction should not be such that it could be described as corrosive, or promote fatigue pitting . These EP additives may be quite safe with ferrous metal surfaces, but may cause severe corrosion on copper alloys, e.g. on bronze worm wheels if for any reason excessive temperatures arise. 

Failure of a Landing Gear Steel Pin A landing gear pin failure occurred in the cylindrical part of the pin whose outer surface was corroded (Sastri et al. (19), p. 515, Fig. 7.78). The fracture surface with convergent chevron patterns at the initiation site and a cover of corrosion product on the surface is shown in Sastri et al. (19, p. 516, Fig. 7.80). Corrosion pits were present at the exterior surface of the cylindrical pin. Pitting corrosion was also present at the fracture initiation site. 

Pitly, D., 2009. Carbon fibre growing as reinforcing material in precast concrete. Carbon Fibre Gear website (http //www. carbonfibregear.com/author/davidpitiyuk/). 

Several PC software programs exkt to aid in lubricant selection to rednce wear, scuffing, and pitting of gear-tooth surfaces. See Specifications and Standards at the end of thk chapter. 

Wear, scoring, material flow, pitting, fracture, creep, and fatigue cause plastic and metal gears to fail. Continuous lubrication can increase the allowable bending stress by a factor of at least 1.5. However there are plastics (acetals, nylons, fluoropolymers, and others) that operate efficiently with no lubrication. There are plastics with wear resistance and durability of plastic gears makes them exceptionally useful. 

The two variable-delivery axial piston pumps k and I for the motions of the ram and the piercing mandrel are driven by a common motor and arranged on the top of the frame directly above the main cylinder. The oil collector tank and two geared pumps for the auxiliary drives are arranged in a pit below floor level. The auxiliary drive units operate the container and die-carrier shifting devices, the shear, the locking mechanism of the die-carrier and the control gears of the two axial piston pumps. 

School of Engineering, Cardiff University, Cardiff CF24 3TA, UK, e-mail snidler cf.ac.uk Keywords gears, scuffing, pitting, friction, elastohydrodynamic lubrication. 

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