Fatigue Damage Sensitivity Computation for Mechanical Design
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Solution Overview
Problem
Current computer-aided design systems for mechanical products are limited in handling non-proportional fatigue loading and critical plane analysis, requiring substantial code changes and analytical derivative computations, which are impractical for mechanical loads.
Innovation Solution
A computer-implemented method for designing mechanical products that computes fatigue damage and sensitivities over a finite element model using finite difference approximations, allowing for updates in design variables to optimize product performance, incorporating critical plane analysis and rainflow-counting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pre-coded fatigue calculation schemes are used, then implementation is simplified, but flexibility to handle non-proportional loading and critical plane analysis is lost
Solution Approach 1:
The patent implements a universal fatigue calculation framework that can handle multiple fatigue theories (Walker, Brown-Miller, Critical Plane) and loading conditions (proportional, non-proportional, variable amplitude) through a single adaptable algorithm structure, eliminating the need for separate pre-coded schemes for each case
2Measurement precision
If analytical derivative computations are used, then sensitivity calculation is exact, but computational complexity and implementation difficulty increase
Solution Approach 1:
The patent replaces complex analytical derivative computations with numerical differentiation techniques (finite differences) that approximate sensitivities through small perturbations in design variables, eliminating the need for complex analytical formulations while maintaining sufficient accuracy for optimization
3Measurement precision
If critical plane analysis is implemented, then fatigue damage assessment accuracy is improved, but computational cost and code complexity increase
Solution Approach 1:
The patent segments the fatigue damage assessment into independent steps: stress computation, fatigue parameter calculation for each critical plane, and damage accumulation, allowing critical plane analysis to be integrated systematically without overwhelming code complexity
Data Source
AI summary
A computer-implemented method for designing a mechanical product formed in one or more materials including obtaining inputs including a finite element model representing the mechanical product and having an initial value of design variables, one or more load cases, a corresponding load history for each load case, boundary conditions, fatigue properties of the one or more materials, and a fatigue calculation scheme. The method further includes computing a distribution of fatigue damage over the finite element model based on the inputs, computing a distribution of sets of fatigue damage sensitivities over the finite element model based on the computed distribution of fatigue damage, each fatigue damage sensitivity of each set approximating a derivative of the fatigue damage relative to a respective design variable, and updating the value of the design variables based on the fatigue damage sensitivities.