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The paper gives an overview of the local stress design concept for gears related both to bending fatigue for the gear teeth and rolling contact fatigue on the gear flanks. Test results are presented for notch fatigue and rolling contact fatigue on specimens as well as for sintered gears manufactured from the quenched and tempered sintered steels (Fe-1.5Mo) + 0.5C and (Fe-4.0Ni-0.5Mo)+ 0.5C, both at a density of ρ = 7.1 g/cm3. The transferability of notch fatigue and rolling contact fatigue data from specimens, test rollers and fatigue test bars, to gears is presented on the basis of local properties.

In a collaborative investigation of ZF Friedrichshafen AG and the Fraunhofer-Institut für Betriebsfestigkeit LBF [1], both constant and variable amplitude fatigue tests were performed on induction-hardened automatic transmission shafts made from Ck 35 mod. steel. The objectives of the project were to evaluate the safety reserves of the shafts and to apply several selected methods to assess fatigue life, to compare these methods and to gain insights for future component developments.

For the development of new components, design engineers today have access to a broad amount of fatigue data, which were obtained from unnotched and notched specimens. These data can be transformed when the conditions of material, strength, geometry, surface and surface layer and loading mode in the fatigue critical areas are taken into account for constant and variable amplitude loading. The procedure of data transferability is discussed for the example of a randomly loaded truck stub axle where the failure criterion is the first detectable crack, and the local equivalent stress/strain and the maximum stressed/strained material volume are considered. In addition, several problems associated with fatigue life assessment under variable amplitude loading are discussed.

Trends in increasing usage of aluminium-alloys for vehicle safety components require one to summarize the state of the art related to the approval of their service strength including the aspects of reliability and safety. For this, it is necessary to describe the design criteria for the vehicle safety components manufactured from aluminium alloys, which include the evaluation of the structural yield point, the fracture behaviour and the fatigue life - three main parameters for the components- service strength. In this paper the procedures for the experimental and the numerical service strength evaluation of cast, forged and welded aluminium-alloy safety components are presented. Also the results of investigations of environmental influences (corrosion, elevated temperature) as well as the methods for accelerated test approval are presented, validated and a practical approach recommended.

Rolling contact fatigue tests with a sliding of -24% were performed with the mixed alloys Fe+1.5%Cu, carbonitrided, Fe+1.5%Cu + 0.5%C, as-sintered as well as quenched and tempered, diffusion alloyed powder Fe-4.0%Ni-1.5%Cu-0.5%Mo, as-sintered, plasmanitrided, carbonitrided, case hardened and additionally mixed with 0.5%C and prealloyed powders Fe-4.0%Ni-0.5%Mo and Fe-1.5%Mo with addition of Cu and C in different heat treatments. The densities investigated were 6.8, 7.1, 7.4 and 7.8 g/cm3. The tribological environment was the gear-box oil SAE 80 at 80°C. With superposition of sliding the highest rolling contact fatigue strength was achieved with powder forged specimens (density of 7.8 g/cm3). An optimum for the sintered specimens in the range of 6.8 to 7.4 g/cm3 was found at around 7.1 g/cm3 for the most sintered steels independent of the heat treatment. This is due to effects based on open and closed porosity in interaction with the tribological environment.

Within the scope of a team work between Kühnle, Kopp & Kausch AG (KKK), Volkswagen AG, Sterling International Technologies Ltd. and the Fraunhofer Institute for Strength of Structures under Operational Conditions (LBF) compressor wheels of aluminium and magnesium investment casting were developed and investigated. Strength and fatigue tests, overspeed and field tests as well as metallographic checks were made in addition to the finite element calculations to optimize the stress under centrifugal forces in an appropriate way for the materials involved. The results and the knowledge gathered are to clarify whether magnesium alloys are an appropriate replacement for the proven standard aluminium alloy for turbochargers.

The paper presents first how load spectra of antilock brake and electronic traction control systems (ABS/ETC) are obtained from braking pressure simulation in special test benches for particular vehicles of different customers. Subsequently, the measures for the derivation of a test spectrum under consideration of a reasonable test time reduction are described. Finally, the experimental and numerical procedures for fatigue life and safety assessments of the ABC/ETC hydraulic housings are presented.