Residual Stress Characterization via Digital Image Correlation
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Solution Overview
Problem
Current methods for characterizing residual stresses in aeronautical parts, such as 3D-woven composite material fan blades, are inefficient, leading to geometrical deviations, material waste, and costly iterations in design, and are limited by destructive testing methods that cannot be routinely used in production.
Innovation Solution
A method involving digital image correlation to measure displacement fields and finite element simulation to determine stress fields, allowing for non-destructive characterization and predictive modeling of mechanical parts, reducing the need for iterative mold design and enabling routine testing of material health without altering the parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If destructive testing methods (drilling holes) are used to check residual stresses, then stress information can be obtained, but the part is destroyed and cannot be used for routine production testing
Solution Approach 1:
The patent replaces destructive mechanical drilling methods with non-destructive optical measurement techniques. Digital image correlation and speckle interferometry are used to measure surface deformations and calculate residual stresses without physically altering the part, thus maintaining part usability while achieving stress detection.
Solution Approach 2:
The patent introduces an intermediary measurement system consisting of speckle patterns and optical fields. These intermediaries allow indirect measurement of residual stresses through optical interference and correlation techniques, avoiding direct mechanical intervention that would destroy the part.
2Manufacturing precision
If iterative mold design is used to compensate for geometrical deviations, then geometry accuracy can be improved, but time and material are wasted through multiple iterations
Solution Approach 1:
The patent applies preliminary characterization of residual stresses during the design phase using non-destructive measurement methods. By measuring and analyzing residual stresses before final production, the design can be optimized in advance to compensate for expected deformations, eliminating the need for multiple iterative mold modifications.
Solution Approach 2:
The patent implements a feedback mechanism where residual stress measurements from prototype or test parts are used to update and refine the design model. This feedback loop allows accurate prediction and compensation of geometrical deviations in subsequent production without requiring physical iterations of mold construction.
3Measurement precision
If simple geometry parts are tested with destructive methods, then stress characterization is possible, but complex aeronautical parts cannot be routinely tested
Solution Approach 1:
The patent develops a universal non-destructive measurement system that can characterize residual stresses in parts of any geometric complexity. The digital image correlation and optical interferometry methods work on both simple and complex aeronautical components, providing a multi-functional solution that replaces geometry-limited destructive methods.
Solution Approach 2:
The patent creates optical copies (speckle patterns and interference fringes) of the part surface that encode deformation information. These optical copies can be captured and analyzed digitally, allowing stress characterization of complex geometries without physical contact or modification of the actual part.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method facilitates faster and more cost-effective design by providing accurate residual stress information, reducing material waste and enabling routine non-destructive testing of production parts, without the need for destructive methods.
Implementation Method 1
determining the displacement field between the first state and the second state of the part by a digital image correlation method
Data Source
AI summary
A method for characterizing a mechanical part making it possible to evaluate the residual stresses in the part, as well as a method for constructing a predictive model and a non-destructive testing method making it possible to easily test such a part, the characterizing method including the following steps: measuring geometrical information of the part in a first state, physically transforming the part between the first state and a second state, measuring geometrical information of the part in its second state, determining the displacement field between the first state and the second state of the part by a digital image correlation method and obtaining the deformation field between the first state and the second state of the part, determining the stress field in the second state of the part by a finite element simulation method.