Transparent Indenter Creep Test Apparatus
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Solution Overview
Problem
Conventional creep test methods require extensive time and struggle to simultaneously determine creep index n and creep constant k due to difficulties in measuring contact area and stress during indentation creep tests.
Innovation Solution
A measurement apparatus and method that uses a transparent indenter with an image capturing device to analyze the contact area, allowing for the calculation of viscoelastic contact area and stress, enabling the simultaneous determination of creep index n and creep constant k through linear regression analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional uniaxial creep testing is used to determine creep index and creep constant, then measurement precision is improved, but productivity deteriorates due to requiring multiple separate tests
Solution Approach 1:
The patent combines multiple creep tests with different stress levels into a single indentation test by applying a loading history that includes multiple stress levels sequentially. This allows determination of both creep index and creep constant from one test rather than requiring multiple separate tests, thereby improving productivity while maintaining measurement precision.
Solution Approach 2:
The patent changes the stress parameter dynamically during the test by applying a loading history with multiple stress levels. This enables extraction of creep behavior at different stress conditions from a single test, improving testing efficiency while preserving the ability to accurately determine creep physical properties.
2Device complexity
If indentation depth is used as alternative to contact area measurement, then device complexity is reduced, but measurement precision deteriorates due to conversion formula requirements
Solution Approach 1:
The patent replaces the mechanical measurement approach (direct contact area measurement requiring complex imaging systems) with an optical interference-based method. The transparent indenter allows light transmission, and interference patterns are used to determine contact area, reducing device complexity while maintaining or improving measurement precision.
Solution Approach 2:
The patent utilizes optical interference color patterns that appear when light passes through the transparent indenter and reflects off the contact interface. These color/fringe patterns provide direct visual information about contact area, eliminating the need for complex mechanical measurement systems while achieving high measurement precision.
3Ease of operation
If theoretical solution is used for surface deformation parameter, then ease of operation is improved, but measurement precision deteriorates due to approximation errors
Solution Approach 1:
The patent replaces the theoretical approximation approach with direct optical measurement using interference patterns. The fringe patterns provide direct information about surface deformation and contact area, eliminating the need for theoretical solutions and their associated approximation errors, while maintaining ease of operation.
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
Enables easy and quick evaluation of creep physical property values by directly measuring contact area and stress under constant load, removing the influence of plasticity and avoiding the need for complex parameter measurements.
Implementation Method 1
a constant-load compression device comprising a transparent indenter (4) including one protrusion on its tip... an image capturing device (7) configured to optically capture an image including a contact area portion
Data Source
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AI summary
A measurement apparatus for carrying out an indentation creep test on a specimen, including a measurement control apparatus that includes a load measurement device configured to measure a load, a constant-load compression device configured to compress a tip of a transparent indenter to a surface of the specimen, and an image capturing device configured to optically capture an image including a contact area portion which is a part of the specimen to which the load is applied by the constant-load compression device; and including an information processing apparatus that includes an image analysis unit configured to analyze a contact area, and a physical property value calculation unit. The physical property value calculation unit includes a first calculation unit configured to subtract a plastic contact area to be obtained analytically from the contact area so as to calculate a viscoelastic contact area, a second calculation unit configured to calculate contact stress based on the viscoelastic contact area and the constant load value, and a third calculation unit configured to calculate a contact strain rate based on the viscoelastic contact area, the physical property value calculation unit being configured to conduct linear regression with respect to a plot of a logarithmic value of the contact stress and a logarithmic value of the contact strain rate so as to determine a creep index n and creep constant k. Accordingly, it is possible to evaluate a creep index n and a creep constant k, which are creep physical property values, simultaneously, easily, and quickly.