Modelling and Finite Element Analysis of a Ball Screw of an Electromechanical Flight Control Actuator to Investigate Mechanical Properties

Kurzfassung

This thesis presents a thorough finite element investigation of a ball screw assembly utilized in an electromechanical actuator for primary flight control, with a focus on evaluating mechanical behavior under different operating conditions. The objective of this study is to evaluate axial and torsional stiffness, efficiency, and backlash phenomena through high-fidelity static simulations in the finite element software ANSYS. A parametric modeling strategy was employed to capture detailed ball-groove contact interactions and assess the influence of varying boundary conditions, friction coefficients, and geometric clearances. In order to reach a conclusion regarding torsional stiffness determination, both direct torquedriven simulations and indirect conversions from axial stiffness models are compared to each other. The findings indicate that the indirect approach systematically underestimates effective torsional stiffness, a phenomenon attributable to the simplified loading path and diminished contact coupling. Furthermore, mechanical efficiency is analyzed under various contact formulations. The investigation reveals that contact status, specifically the distinction between sticking and sliding, exerts a substantial influence on frictional dissipation energy. This influence frequently overshadows the coefficient of friction in quasi-static regimes. In order to explore backlash phenomena, a dedicated model is introduced. While static simulations are capable of qualitatively capturing force decay and contact disengagement, they are limited in their ability to resolve the angular closure associated with backlash. A variety of strategies are investigated to enhance backlash modeling, including modified contact definitions and alternative friction treatments. Prospective avenues for future research include the implementation of dynamic friction models, velocity-controlled simulations, and rigid-deformable body modeling. This work establishes finite element models that capture the mechanical behavior of ball screw assemblies and offers a platform for future developments, including dynamic modeling, and reduced-order representations. The insights gained serve as a valuable reference for the evaluation of performance in aerospace applications.