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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.

Newly developed sintered steels, combined with new densification processes, make the P/M process a candidate for highly loaded gears or similar components. There is a great need to develop methods which support design engineers with well established and standardized data. Furthermore, the challenge of the global market requires comparable material data and international standards. The absence of this data forces the engineer to use higher safety factors, risk poor reliability, or perform costly tests. The paper describes principle differences in the behavior of porous and non-porous materials under rolling contact conditions. The methods for determining RCF will be critically reviewed in regard to the special needs of P/M materials. Test results on P/M and wrought materials will be discussed. The paper introduces the ZF-RCF test bench, developed by ZF-Friedrichshafen (Germany) and the Gear Research Institute in Munich (Germany).