Periodic Reporting for period 3 - MatCH4Turbo (Material Model of Case-Hardened Steels for Turbo Gear Applications)
Periodo di rendicontazione: 2022-04-01 al 2023-12-31
Based on the drawings of the test rig the external manufacturing of the housings, shafts and seals was tendered and commissioned. Due to the high estimated costs of these parts, an extensive tendering process was necessary. Furthermore, the other test rig components and components for test preparation, e.g. the oil aggregate, the drive motor and a balancing machine, were tendered and ordered. Performance analyses of the test rig were carried out. The thermal and dynamic operational behavior was simulated and the safe operation ensured.
The test rig components were manufactured and procured and the test rig was successfully assembled. The test rig was successfully commissioned up to a maximum speed of 12000 rpm.
During the final stages of commissioning, scuffing damage occurred to the axial journal bearing, which prevented the investigations from proceeding. The procurement of a replacement bearing went beyond the end of the project term. Accordingly, a short series of tests was carried out on the pulsator test rig for risk mitigation purposes in order to still have gear test data.
The manufacturing of the standard test specimens and the test gears from both materials was finished.
For the understanding of relevant local failure probabilities and mechanisms at up to 10^9 load cycles a VHCF model was developed by Leibniz-IWT. The experimental approach includes fatigue and crack growth investigations on simplified geometries to examine the influence of different carbon contents on the material properties of case-hardening steels under cyclic loading. The model taks into account the weakest link concept and was fully built up at the IWT. To build the model, compact tension tests and axial HCF tests were carried out with the different hardness states for both materials. On the part of the WZL, simulations of the local tooth root stress and a complete gear tooth characterization (hardness depth curves, residual stress measurements) contributed to the development of the material model.
The virtual design process for high performance machine elements based on an FE-analysis leads above all to a significantly accelerated and resource-efficient design process. With tools provided in this project, functional tolerances and surface/subsurface characteristics can be pre-defined in the design process to ensure a safe operation of the machine element. Besides productivity, the manufacturing quality can be increased at the same time as tolerances are better controlled. Due to the validated and data-based VHCF calculation model, it is possible to realize gears with reduced geometric dimensions, whereas the transmission of a high power density can be realized. This results in weight savings potential, which in turn leads to higher transport capacity and reduced emissions of the aircraft.