Design methods for reliable fatigue assessment of PM components |
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Authors: | J. Baumgartner K. Lipp T. Bruder H. Kaufmann |
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Affiliation: | Fraunhofer Institute for Structural Durability and System Reliability LBF, Bartningstra?e 47, 64289 Darmstadt, Germany |
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Abstract: | The use of PM materials is rapidly expanding with an increasing concentration on highly loaded structural parts such as synchroniser hubs, gears, sprockets or shifting forks. The successful implementation of PM materials for such parts depends on a reliable fatigue design concept. Such a design concept has to consider the local durability, especially in fatigue critical sharply notched areas, depending on the local density of the material and stress gradients. This paper summarises different design methods in order to transfer the fatigue behaviour of specimens to components by considering sharply notched areas. Four different local approaches have been investigated: the highly stressed volume approach, the stress gradient approach, the critical distance method and the stress averaging method according to Neuber. The design methods have been analysed on the basis of fatigue testing results of unnotched and notched fatigue specimens and of synchroniser hubs made from a 4% Ni diffusion‐alloyed steel material (Distaloy AE+0.6%C). The transferability of characteristic fatigue properties from specimens to a sharply notched component, a synchroniser hub, is presented and the practicability of the design methods demonstrated and discussed. These investigations showed that the most reliable concept was the highly stressed volume approach. The accuracy of the approach can be comprehended separating statistical and so called material support effect. |
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Keywords: | PM steels fatigue assessment methods highly stressed volume size effect Sinterstahl Schwingfestigkeit Bemessungskonzepte hö chst beanspruchtes Volumen Grö ß eneinfluss |
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