Generative 3D Shape Optimization Under Fatigue Thickness Constraints
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Solution Overview
Problem
Current CAD software limitations in generative design for additive and subtractive manufacturing fail to effectively optimize 3D structures for size-limited fatigue damage, as they do not directly operate on exact surface boundary representations, leading to inefficiencies in simulating and manufacturing structures that can withstand fatigue without catastrophic failure.
Innovation Solution
A computer-aided design program iteratively modifies 3D shapes based on design criteria, including fatigue constraints, by performing numerical simulations, calculating stress and strain elements, and redefining fatigue safety factors to enforce minimum thickness and volume fraction constraints, using level-set representations and PID controllers for stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If B-Reps are sampled and replaced with volumetric representations such as level sets or meshes, then computational efficiency for physical simulations is improved, but manufacturing precision and surface accuracy deteriorate
Solution Approach 1:
The design process is segmented into distinct phases: generative design and optimization using volumetric representations (level sets/meshes) for computational efficiency, followed by a conversion phase to B-Rep format for manufacturing precision. This segmentation allows each phase to use the most appropriate representation type for its specific requirements.
Solution Approach 2:
The patent introduces an intermediary conversion process that transforms the optimized volumetric representation into an exact B-Rep format. This intermediary step acts as a bridge, preserving the computational benefits of volumetric methods while delivering the surface accuracy required for manufacturing.
2Quantity of substance
If generative design optimizes for minimum weight or volume, then material usage is reduced, but structural reliability under fatigue loading deteriorates
Solution Approach 1:
The patent changes the optimization parameters to include fatigue-based constraints (minimum thickness, volume fraction) alongside traditional objectives. This allows the generative design to explore weight reduction while maintaining reliability through physically-based failure criteria rather than simple stress constraints.
Solution Approach 2:
The patent replaces traditional mechanical stress-based design criteria with a more comprehensive fatigue damage model that incorporates crack growth mechanics and damage tolerance principles. This substitution enables better prediction of actual fatigue behavior while optimizing material usage.
3Reliability
If design constraints enforce minimum thickness based on critical fatigue crack length, then fatigue damage is limited, but design flexibility and weight optimization deteriorate
Solution Approach 1:
The patent implements dynamic, spatially-varying thickness constraints rather than uniform minimum thickness requirements. The constraints adapt locally based on the critical fatigue crack length at each location, allowing the design to be flexible where fatigue damage is tolerable and more restrictive where it is critical, thus maintaining design freedom while ensuring reliability.
Data Source
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AI summary
Methods, systems, and apparatus, including medium-encoded computer program products, for computer aided design of physical structures using generative design processes, A method includes obtaining, by a computer aided design program, a design space for a modeled object, one or more design criteria for the modeled object, one or more in-use load cases, and a critical fatigue crack length for a material from which A physical structure will be manufactured; iteratively modifying a generatively designed three dimensional shape of the modeled object in the design space in accordance with the critical fatigue crack length for the material, wherein the iteratively modifying comprises enforcing a design criterion that limits a minimum thickness of the generatively designed three dimensional shape, the minimum thickness being based on the critical fatigue crack length for the material.