Service Load and Stress Distribution for P/M Gear Components

For the introduction of gear components from new materials manufactured with innovative technologies, reliable methods and data are needed to meet the requirements of modern light weight design. Data about the mission profile of the components in the drive line of passenger cars have been worked out by the European car industry based on the input and output torques. Loading and stress conditions inside of the gears, however, are not known in detail very much.

This paper reports about extensive service measurements on the synchronization components of a gear of a passenger car. The short time measured data were evaluated by the results of long term measurements of the input and output torques on a large variety of passenger cars. Finite element calculation verified by the strain measurements was used to determine stress conditions in critical areas of the components based on the stress conditions in the measuring cross sections. By both data, the short time measurements of stress conditions on the components and the long term mission profile measurements, the design spectra for the components were defined. On the components the measurements detected stress conditions created by the engine torque and super-imposed stress cycles with respect to the revolution due to local deformation inside the gear. Therefore, a superposition of the spectra of dynamic torque cycles and revolutions on the torque level was worked out. A subsequent damage assessment was performed with the derived superimposed spectrum with respect to the allowable fatigue strength derived from specimen testing. Thus, a methodology for the dimensioning of gear components was demonstrated based on short time measurements, customer usage data and finite element calculations as well as fatigue strength data from specimen testing.