Component strength of heat treated sintered steel
Up to now, no concept exists for the computational strength verification of components made of porous sintered steel. Therefore, the aim of this project was to develop a computational strength verification for sintered steels. In doing so, the calculation should be possible for as wide a range of different alloy compositions as possible. In order to make the calculation as simple as possible for the user, a further requirement was the inclusion of fewer input parameters in the calculation algorithm. Density and hardness are included as material properties in the calculation rule.
The highly stressed volume (component geometry & load), as well as the stress ratio, were selected as stress variables. In order to develop a computational strength verification, an extensive literature search was first conducted to gather a variety of Wöhler lines. An attempt was made to extract as much metadata as possible from the sources for each test series, such as the alloy composition, density and hardness, specimen geometry, etc. In addition, for each extracted Wöhler line, the stress quantities highly stressed volume, highly stressed surface area, stress integral, shape number and related stress gradient were determined by FEA. The quantities are obtained from the applied specimen geometry, external load and stress ratio.
The data thus extracted and determined were compiled in a machine-readable database. To date, there are no systematic studies in the literature on the fatigue behavior of hardened sintered steels. Therefore, in this project, hardened and case-hardened material samples were systematically fabricated and Wöhler lines with different boundary conditions were determined.
The data sets generated in this way were able to supplement the above-mentioned database. With the aid of the extensive database, it was possible to develop evaluation approaches for sintered steels that are independent of the alloy composition on the basis of easily measured parameters. Approaches for static and cyclic loading could be determined. With the input quantities density and hardness, as well as the local stress parameters, it is now possible to generate a synthetic Wöhler line and a design Wöhler line if the above-mentioned quantities of the sintered steel are known. Due to the size and versatility of the compiled database, two different approaches (LBF and IWM) could be established, which provide qualitatively similar results. To validate the calculation approaches, component tests were carried out on two different model components.
Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit (LBF), Darmstadt
FundingCopyright: © BMWi
The IGF project 20234 N of the Research Association Forschungskuratorium Maschinenbau e.V. - FKM, Lyoner Straße 18, 60528 Frankfurt am Main, Germany, was funded by the German Federal Ministry of Economics and Climate Protection through the German Federation of Industrial Research Associations (AiF) as part of the program for the promotion of joint Industrial Collective Research ("Industrielle Gemeinschaftsforschung", IGF) on the basis of a resolution of the German Bundestag. The final report of the project FKM 614 can be obtained from the Forschungskuratorium Maschinenbau (de) (FKM) e. V. (postal address: Lyoner Str. 18, 60528 Frankfurt am Main, e-mail: firstname.lastname@example.org, phone: +49 69 6603 1681).