Virtual Grid Stress Intensity Factor Evaluation
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Solution Overview
Problem
Generating high-quality finite element meshes near complex crack tips is time-consuming and challenging, especially for three-dimensional nonplanar cracks, leading to inaccurate stress intensity factor evaluations in existing methods.
Innovation Solution
A stress intensity factor evaluation system using a virtual grid, which includes a virtual grid generation unit, nodal displacement calculation unit, stress field calculation unit, and stress intensity factor evaluation unit, allowing for accurate stress field calculation and stress intensity factor determination even with low-quality meshes through interpolation and least squares methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-quality finite element mesh is generated near crack tip, then stress intensity factor evaluation accuracy is improved, but mesh generation time and effort increase significantly
Solution Approach 1:
The domain is divided into two distinct parts: a virtual grid domain surrounding the crack tip where high accuracy is needed, and the surrounding finite element mesh domain. This segmentation allows applying different meshing strategies to different regions, achieving high accuracy at the crack tip without requiring the entire domain to have high-quality mesh.
Solution Approach 2:
A virtual grid is introduced as an intermediary structure between the crack tip and the surrounding finite element mesh. This virtual grid serves as a mediator that captures the singular stress field behavior near the crack tip using simple geometric shapes, while the surrounding mesh handles the broader domain. The two domains are coupled through displacement compatibility conditions at their interface.
2Measurement precision
If high-quality finite element mesh is generated for complex crack shapes, then stress field accuracy is improved, but complexity of mesh generation process increases
Solution Approach 1:
The complex mesh generation problem is segmented into two parts: generating a simple virtual grid around the crack tip (which can be done automatically without user intervention) and generating the surrounding finite element mesh (which can use standard meshing algorithms). This segmentation avoids the need to generate a single complex high-quality mesh that conforms to arbitrary crack geometries.
Solution Approach 2:
Different mesh quality requirements are applied locally to different regions. The virtual grid region near the crack tip uses a simple, regular structure that is easy to generate, while the surrounding region uses the original finite element mesh. This local differentiation allows each region to have appropriate mesh characteristics without requiring the entire domain to meet the most stringent quality requirements.
3Productivity
If standard finite element analysis is used with low-quality mesh, then analysis speed is improved, but stress intensity factor accuracy deteriorates
Solution Approach 1:
The analysis domain is segmented such that the virtual grid region handles the stress concentration analysis with simple geometry (enabling fast computation), while the surrounding finite element region handles the broader structural response. This segmentation allows the critical near-tip region to be analyzed with a computationally efficient virtual grid structure.
Solution Approach 2:
The virtual grid uses a regular, structured geometry with uniform element sizes, which simplifies the numerical computation compared to irregular finite element meshes. This parameter change in mesh structure (from irregular to regular) improves computational efficiency for the stress intensity factor calculation while maintaining accuracy through the specialized virtual grid formulation.
Data Source
AI summary
Disclosed herein is a stress intensity factor evaluation system using a virtual grid in which a control server having a computational function is executed via a computer. The control server includes: a virtual grid generation unit configured to generate a virtual grid; a nodal displacement calculation unit configured to calculate the nodal displacement of the generated virtual grid; a stress field calculation unit configured to calculate the stress field of the virtual grid; and a stress intensity factor evaluation unit configured to calculate a J-integral value and a stress intensity factor.