Optimization of the application behaviour of spur gears by machine-hammered tooth surfaces (OptiGear)

Key Info

Basic Information

01.01.2018 to 31.12.2020
Organizational Unit:
Chair of Manufacturing Technology, Forming Technologies
German Research Foundation DFG



Lars Uhlmann

Research Assistant


+49 241 80 27428



Spur gears are gears with axially parallel toothing and are widely used as functional components in manual car transmissions and industrial transmissions. In gearboxes, the spur gears are set against each other in such a way that their teeth roll against each other during rotation. Since only one to three teeth are in contact as a rule, an insufficiently corrected tooth shape can result in impact meshing in the rolling contact, which is referred to as sliding. This has a negative influence on the tooth flank load-bearing capacity, the tooth root load-bearing capacity and the vibration excitation. In the case of involute-toothed spur gears, slippage of the tooth flanks is minimized, but tribological wear of the tooth flank surfaces can occur over the service life of the spur gears.

By optimizing the tooth flank contact from a tribological point of view, both an increase in the tooth flank carrying capacity and an increase in the efficiency of a spur gear can be achieved. MOH is an industrial process used for the surface treatment of highly stressed components. The MOH is used to smooth or structure the surface, to index residual compressive stresses and to strain harden the surface. In addition, MOH structures improve the tribological properties of the surfaces. The MOH has been incompletely researched as a method for the optimization of friction and wear of the rolling contact of highly loaded gears. The cause-effect relationships between the process kinematics of hammering and the resulting surface structures as well as the effects of these surface structures on the elasto-hydrodynamic lubrication condition and the wear resistance of rolling contacts are not known.

In this research project the modification of the surface integrity of case-hardened tooth flank analogy samples from 16MnCr5 due to MOH machining is investigated and cause-effect relationships between MOH process parameters and the resulting surface integrity are explained. Subsequently, the influence of the edge zone modification on the tooth flank load carrying capacity, friction and wear in the two-disc test bench as well as in numerical finite element simulations is investigated.