A Framework to Implement Probabilistic Fatigue Design of Safe-Life Components

Abstract

Safety-critical components, such as aircraft landing gear, are designed using the 'safelife' fatigue analysis process. Variability exists within materials data, loads data and component dimensions and is currently mitigated using safety factors. Probabilistic approaches to safe-life fatigue design have been proposed to better represent this variability. However, challenges currently exist that prevent the wider utilisation of a probabilistic approach. This paper presents a framework that aims to overcome these challenges. The statistical characterisation, probabilistic, surrogate modelling and sensitivity analysis methods required to implement the framework are introduced. Finally, a discussion of how recent advances within aerospace fatigue design, such as 'big-data', can be used to support a probabilistic framework is presented.

Certification Approach for Physics Informed Machine Learning and its Application in Landing Gear Life Assessment

“…The algorithm should be able to categorize input data with respect to its importance to the end result and the evaluation of the fatigue damage limits of the landing gear as well as compare validated values of stress and loading with the filtered input data in order to result with a precise final value, e.g. with the use of probabilistic approaches [11] . For the control of data and the optimization of its importance to the end result, Higgins et al recommend the usage of 'fencing' wherein a three-step approach includes:…”

Landing gear ground manoeuvre statistics from automatic dependent surveillance-broadcast transponder data

“…Within existing landing gear fatigue design practice, the occurrence and sequencing of ground manoeuvres and their resulting loads must be accounted for within the landing gear load spectrum (3,4,5,6,7) . The definition of a landing gear load spectrum is required to provide the cyclic loads applied to the landing gear to support fatigue design, analysis and substantiation activities (2,8) . Currently, the construction of landing gear load spectra requires assumptions to be made regarding the variability of ground manoeuvre occurrence and sequencing (5,6,9) .…”

“…In addition, sensitivity analysis methods have been applied to landing gear loads to identify the most influential flight and aircraft parameters regarding landing gear loads during hard landings (14) . The load factors applied to landing gear during specific manoeuvres are typically represented using exceedance curves (3) , such that ‘blocking’ can be performed to construct the load spectrum (8) . Exceedance curves have been produced for specific landing gear loads by Laddda and Struck (2) and Buxbaum (3) for a wide-body civil aircraft.…”

“…In addition, existing assumptions must be validated and challenged to ensure that they are not over-conservative, resulting in a less optimum design. A challenge of potential load spectrum conservatism could support the design of more efficient landing gear components which are still safe and reliable in-service (8) .…”