Analyse the Influence of Contact Loads between Gear Teeth on the behaviour of Crack Path

Abstract

The geared turbofan engines rely on their gears to perform efficiently and reliably. Safety is the top priority in aviation engines, as any failure can put the aircraft and passengers at risk. Hence, conducting a detailed analysis of potential gear failure, including crack propagation, is crucial to ensure the continued success and advancement of geared turbofan ngine technology. The main goal of this thesis is to thoroughly examine the complexities of gear design and simulation, focusing on analyzing the impact of cracks in gear teeth. This thesis provides a detailed application of the methodologies employed to evaluate gear performance and durability, leveraging intricate simulation setups including full-gear, five-teeth, and one-tooth submodels, and utilizing Time-varying mesh stiffness (TVMS) loads in Finite element (FE) simulations. The study revealed the impacts of different preloads on stress levels, and it demonstrated axial-only preloads under 0.02mm as optimal. In the fatigue study, high torque conditions facilitated the identification of potential initial crack locations. The Stress intensity factor (SIF) study emphasized calculating the peak load affected crack propagation and stress ratio experienced by the crack in cyclic loading. Crack propagation was analyzed using ANSYS© SMART crack propagation tool with submodeling techniques. It delved into the effects of different initial crack geometries and preload conditions on the rate and direction of crack propagation. The extended crack propagation method systematically simulates crack growth over multiple cycles, overcoming computational limitations and accounting for load fluctuations. The preload analysis underscored the pivotal role of axial and radial preloads in influencing stress intensity factors and crack extension rates. It revealed that while radial preload can accelerate crack growth towards risky pathways, axial preload, especially under 0.02mm, can direct the cracks towards safer paths, balancing structural integrity with operational efficiency. Furthermore, a test rig validated the numerical simulations, employing strategically placed strain gauges to monitor stress levels in real-time under various preload conditions, ensuring reliable data acquisition and immediate response to critical stress levels.