Performance optimization of spur gears by machine hammered tooth surfaces (OptiGear2)

• Applicant: Professor Dr.-Ing. Thomas Bergs
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 390969378

Spur gears are gear wheels with axially parallel gearings and they are widely used as functional elements in automotive and industrial transmissions. In gear boxes spur gears are adjusted against each other so that their teeth roll over during the rotation. During meshing of two spur gears there are usually one to three teeth in contact so that shock-loading may occur if the teeth shape is not appropriately corrected. The shock-loading is called slipping. The flank and the root bearing capacity as well as the vibration stimulation are negatively influenced by the slipping. By the use of involute toothed spur gears the slipping can be minimized but over the lifetime of spur gears tribological wear of the tooth flank surfaces occurs. By improving the tribological system of the contact area of tooth flanks the flank bearing capacity and the efficiency of the transmission can be improved. Machine hammer peening (MHP) is an industrially used process for surface treatment of highly loaded elements. By means of machine hammer peening, surface smoothing, residual compressive stresses and strain hardening induction in the surface layer is obtained. Furthermore, tribological characteristics of surfaces can be improved by means of MHP. MHP is insufficiently investigated for the optimization of friction and wear in rolling contact of highly loaded spur gears. The cause and effect correlations between MHP process kinematics and the resulting surface structures as well as the effects of these surface structures on the elasto-hydrodynamic lubrication conditions and wear resistance of rolling contacts are not known. A basic research on this matter needs to be done in order to identify, quantify, and explain the tribological mechanisms of structured surfaces in highly stressed rolling contacts. Based on these results the impact of hammered surface structures on the flank bearing capacity, friction, and wear must be experimentally and numerically investigated, and explained. As the MHP is an elasto-plastic pressure forming process, the resulting interaction between the strain hardening and the root bearing capacity as well as the plastically deformed tooth profile must be investigated.

• DFG Programme: Research Grants