Crushable Core Compression Fixture for Optical Strain Testing
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Solution Overview
Problem
Existing compression testing methods for large notch compression test panels of air vehicle components are inefficient due to the need for extensive installation time and labor for strain gages, obstruction of optical strain measurement systems, and wear out of base components, leading to increased costs and reduced testing rates.
Innovation Solution
A compression testing apparatus with a rigid base assembly, a support assembly featuring grid portions with window openings for optical strain measurement, and a crushable core assembly to stabilize and protect the test specimen, allowing for direct optical strain measurement and reduced setup time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gages are used to measure strain of the test specimen panel, then strain measurement can be achieved, but extensive installation time and labor are required, resulting in increased flow time and reduced testing rate
Solution Approach 1:
The patent replaces the mechanical strain gage system with an optical strain measurement system. The support plates are designed with transparent or translucent regions that allow optical access to the test specimen, enabling non-contact optical measurement methods (such as digital image correlation or other optical techniques) to measure strain without requiring physical strain gage installation, thereby eliminating the extensive installation time and labor while maintaining measurement capability
Solution Approach 2:
The patent extracts the measurement function from the mechanical support structure by creating transparent windows in the support plates. This allows the measurement function to be performed separately by an optical system rather than being integrated through mechanical strain gages, separating the support function from the measurement function and enabling more efficient optical measurement approaches
2Strength
If support plates completely cover the test specimen panel, then structural support is provided, but optical strain measurement systems cannot obtain information relating to strain measurements
Solution Approach 1:
The support plates are designed with non-uniform optical properties - most areas are opaque for structural support, but specific localized regions are transparent or translucent to allow optical access. This local quality variation enables both structural support and optical measurement functions to coexist by providing optical access only where needed for strain measurement while maintaining overall structural integrity
Solution Approach 2:
The support plates are segmented into opaque structural regions and transparent measurement regions. This segmentation allows different portions of the support plate to serve different functions - the opaque portions provide structural support while the transparent portions enable optical strain measurement, resolving the contradiction between support and measurement requirements
3Device complexity
If a thin base portion is used in the existing test fixture, then the fixture structure is simplified, but the base portion wears out after several compression tests, requiring shimming operations
Solution Approach 1:
The base portion parameters are changed by making it adjustable and replaceable rather than fixed. The base can be shimmed or adjusted to compensate for wear, and can be replaced when excessively worn. This parameter flexibility maintains structural integrity and reliability over time without requiring complete fixture redesign, balancing simplicity with durability
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 solution enables faster testing rates, reduced labor and costs, and improved durability of the testing apparatus by allowing optical strain measurement and minimizing wear on base components, potentially increasing testing capacity by 10 to 20 times compared to traditional methods.
Implementation Method 1
the core assembly being crushable and configured to stabilize the test specimen and protect the support assembly and the base assembly from fracture loads generated by the test specimen adjacent the core assembly during compression testing by absorbing energy that is released sideways from the test specimen upon fracture or breaking of the test specimen
Data Source
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AI summary
There is provided an apparatus (30) for compression testing. The apparatus (30) has a base assembly (60) having an end load element (74) attached to the base assembly (60), the base assembly (60) being rigid. The apparatus (30) has a support assembly (32) attached to the base assembly (60), and having a plurality of window portions (44). The apparatus (30) has a core assembly (46) installed within the support assembly (32), the core assembly (46) being crushable and configured to protect the support assembly (32) and the base assembly (60) from fracture loads (53) generated during compression testing. The base assembly (60), the support assembly (32), and the core assembly (46) together form an apparatus (30) for compression testing of a test specimen (80) having a notch portion (82). The apparatus (30) is configured for use with an optical strain measurement system (120). When the test specimen (80) is installed in the support assembly (32), the test specimen (80) and the notch portion (82) are visible to the optical strain measurement system (120) through the plurality of window portions (44).