PSI - Issue 75

ScienceDirect Available online at www.sciencedirect.com ScienceDirect StructuralIntegrity Procedia (2025) 000 – 000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect StructuralIntegrity Procedia (2025) 000 – 000 Procedia Structural Integrity 75 (2025) 691–708

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www.elsevier.com/locate/procedia

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of Dr Fabien Lefebvre with at least 2 reviewers per paper 10.1016/j.prostr.2025.11.070 2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the Fatigue Design 2025 organizers 2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the Fatigue Design 2025 organizers * Corresponding author. E-mail address: robertgoraj@gmx.de Fatigue Design 2025 (FatDes 2025) Fatigue dimensioning of a bearing cap of an electric motor for a commuter aircraft Robert Goraj a, * a Rolls-Royce Deutschland Lfd & Co KG, Otto-Hahn-Ring 6, 81739 Munich, Germany An aircraft propeller is directly connected to the rotor shaft of an electric motor. Rotating components are axially supported by a bearing cap. A semi-analytical parametric (second moment of area dependent) mathematical model is built using the Laplace transform. The model is implemented in MATLAB to dimension he bearing cap. Static, modal, frequency response and transient analyses are performed on semi-analytical base. The determined mechanical stresses and deformations are verified in NX NASTRAN by means of the finite element method (FEM). Structural results are used as an input for fatigue calculations performed according to the analytical strength assessment guideline of the Cooperative Research Association for Mechanical Engineering (the FKM guideline).Based on optimal material utilization, a geometry of the bearing cap is developed. Using the fatigue software RIFEST, it is demonstrated that the analyzed geometry can withstand 1E7 load cycles due to propeller excitation. Keywords: mechanical dimensioning, optimal material utilization, FKM guideline, electric aircraft 1. Introduction One of most important parameters for components in aircraft applications is the specific power SP (power-to-mass ratio ). For electric motors used in today’s aircraft propulsion, the average SP equals approx.5 kW/kg[1], [2], [3], whiles future aircraft propulsion motors require the SP of approx. 13 kW/kg[4],[5]. An elimination of conventional gearbox can lead to a smaller structural mass of an overall drive system. It can be achieved by applying of the magnetically geared motor drive trains[6], [7], [8], [9], [10]and by a direct coupling of a propeller [11], [12], [13], Fatigue Design 2025 (FatDes 2025) Fatigue dimensioning of a bearing cap of an electric motor for a commuter aircraft Robert Goraj a, * a Rolls-Royce Deutschland Lfd & Co KG, Otto-Hahn-Ring 6, 81739 Munich, Germany Abstract Click here and insert your abstract text. An aircraft propeller is directly connected to the rotor shaft of an electric motor. Rotating components are axially supported by a bearing cap. A semi-analytical parametric (second moment of area dependent) mathematical model is built using the Laplace transform. The model is implemented in MATLAB to dimension he bearing cap. Static, modal, frequency response and transient analyses are performed on semi-analytical base. The determined mechanical stresses and deformations are verified in NX NASTRAN by means of the finite element method (FEM). Structural results are used as an input for fatigue calculations performed according to the analytical strength assessment guideline of the Cooperative Research Association for Mechanical Engineering (the FKM guideline).Based on optimal material utilization, a geometry of the bearing cap is developed. Using the fatigue software RIFEST, it is demonstrated that the analyzed geometry can withstand 1E7 load cycles due to propeller excitation. Keywords: mechanical dimensioning, optimal material utilization, FKM guideline, electric aircraft 1. Introduction One of most important parameters for components in aircraft applications is the specific power SP (power-to-mass ratio ). For electric motors used in today’s aircraft propulsion, the average SP equals approx.5 kW/kg[1], [2], [3], whiles future aircraft propulsion motors require the SP of approx. 13 kW/kg[4],[5]. An elimination of conventional gearbox can lead to a smaller structural mass of an overall drive system. It can be achieved by applying of the magnetically geared motor drive trains[6], [7], [8], [9], [10]and by a direct coupling of a propeller [11], [12], [13], © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of Dr Fabien Lefebvre with at least 2 reviewers per paper Abstract Click here and insert your abstract text. * Corresponding author. E-mail address: robertgoraj@gmx.de