Fatigue Analysis and Load Spectrum Generation for Wing‐Fuselage Lug Joint With a Focus on Human Safety Transport Category Aircraft

ABSTRACT This research work focuses on fluctuating load spectrum generation and fatigue analysis of a wing‐fuselage attachment lug joint, in accordance with the requirements outlined in 14 CFR Part 25 for transport category aircraft. The study involves the generation of a fatigue load spectrum using an exceedance curve, followed by finite element analysis of a simple round‐ended lug. The exceedance curve is a statistical tool used to represent the probability of a variable exceeding a particular threshold over a specified time period. It is particularly useful in fatigue analysis as it helps quantify the likelihood of stress levels surpassing critical limits, aiding in the assessment of structural integrity and durability. The CAD model of the lug is created in CATIA, and the corresponding FE model is obtained using Altair HyperMesh. The investigation pertains to a turboprop aircraft weighing approximately 25,000 kg and accommodating 70–90 seats, with ATR 72 and Dash Q 400 being the prominent choices in this category within India. Mission Profiles for these aircraft are obtained from the Directorate General of Civil Aviation (DGCA) website, utilizing scheduled flight data. To ensure the structural integrity of the lug, a static analysis is performed for FE model convergence, leading to the determination of stress concentration factors. Subsequently, fatigue analysis is conducted using Nastran Embedded Fatigue (NEF), considering constant amplitude loading with stress ratios of −1 and 0.1. the fatigue life of the component is predicted based on Goodman and Gerber failure criteria. The analysis yields crucial insights into the fatigue life of the lug and its damage accumulation over time.