Fatigue Damage Estimation Using Generic Polynomial Functions
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Solution Overview
Problem
Current structural health monitoring methods, particularly for aircraft, are unreliable in predicting fatigue damage due to the inaccuracies of finite element load computer modeling, leading to premature retirement of aircraft and increased costs.
Innovation Solution
Implementing a method that uses a small number of sensors to collect fatigue data during flight trials, which is then used to derive a generic polynomial function via a genetic algorithm to estimate fatigue life in real-time, allowing for accurate predictions without the need for extensive sensor installation on all aircraft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If finite element load computer modeling is used to predict fatigue damage, then the method can be implemented without sensors, but the prediction accuracy deteriorates leading to premature aircraft retirement
Solution Approach 1:
The patent creates a simplified copy of the complex finite element model by deriving equivalent stress functions from comprehensive finite element analysis. These simplified stress functions capture the essential fatigue behavior at critical locations without requiring the full computational complexity, enabling accurate real-time predictions without sensors while maintaining implementation ease
Solution Approach 2:
The patent performs preliminary finite element analysis and ground-based fatigue tests before deployment to derive and validate the simplified stress functions and templates. This preliminary characterization of structural response under various loading conditions enables accurate real-time fatigue damage prediction during actual flight operations without requiring sensors or complex computations
2Measurement precision
If a small number of sensors are installed on test aircraft to collect fatigue data, then prediction accuracy improves, but the cost of sensor installation and maintenance increases
Solution Approach 1:
The patent applies partial action by installing sensors only at critical locations where fatigue damage is most likely to occur, rather than comprehensive sensor coverage throughout the aircraft structure. This selective sensing approach provides sufficient data to validate and calibrate the simplified stress functions while minimizing sensor installation complexity and cost
Solution Approach 2:
The sensors serve multiple functions: they collect real-time strain data for validating the simplified stress functions, provide calibration data for the fatigue damage prediction algorithm, and verify the accuracy of predictions against actual measured data. This multi-functional use of minimal sensors maximizes the value obtained from the sensor installation
3Measurement precision
If extensive sensor installation is performed on all aircraft, then fatigue damage prediction accuracy improves, but the cost and complexity increase significantly
Solution Approach 1:
The patent creates simplified computational copies (stress functions and templates) of the comprehensive finite element model that can be executed with minimal sensor input. These copied models capture the essential fatigue behavior and can be deployed on standard aircraft flight data systems without requiring extensive sensor installations or specialized computing hardware
Solution Approach 2:
The patent extracts only the essential stress characteristics and fatigue damage parameters from the comprehensive finite element analysis, creating simplified stress functions that focus on critical locations and loading conditions. This extraction process removes unnecessary computational complexity and sensor requirements while retaining the core predictive capability
Data Source
AI summary
A method and system method for estimating fatigue damage in a structure obtains fatigue damage data collected using at least one sensor associated with the structure during at least one test operation and also obtains structure use parameter data collected during the at least one test operation. The obtained fatigue data and the obtained use parameter data are used to compute coefficients of at least one generic polynomial function that outputs a fatigue damage value based on inputs representing use parameter data. The at least one generic polynomial function is used to output an estimated fatigue damage value based on inputs representing use parameter data collected during use of the structure.