Non-destructive CTE Measurement via Digital Image Correlation
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Solution Overview
Problem
Conventional methods for measuring thermal characteristics of materials are destructive, require small sample sizes, and can only measure one direction at a time, making them unsuitable for larger structures and anisotropic materials, as well as failing to account for localized thermal gradients common in real-world applications.
Innovation Solution
A method using Digital Image Correlation (DIC) analysis with infrared and optical sensors to measure the coefficient of thermal expansion (CTE) of a test object by capturing reference images, applying thermal loads, and correlating strain information with temperature changes, allowing for non-destructive, scalable measurement of CTE and fiber orientation in various materials and structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional thermal measurement methods (thermal mechanical analysis, dilatometry) are used, then measurement precision is achieved, but the test object is destroyed and only small samples can be measured
Solution Approach 1:
The patent replaces conventional mechanical/destructive measurement methods with an optical measurement system. An optical sensor captures images of the test object before and after thermal loading, and a processor analyzes the images to calculate thermal expansion. This substitution eliminates the need for physical contact and destructive testing while maintaining measurement precision through digital image correlation analysis.
Solution Approach 2:
The patent creates optical copies (images) of the test object's surface before and after thermal expansion. By analyzing the displacement of features between these images through digital image correlation, the system determines thermal expansion characteristics without physically altering or destroying the test object. This copying approach enables non-destructive measurement of larger structures.
2Measurement precision
If conventional methods are used, then measurement precision is achieved, but only one direction can be measured at a time
Solution Approach 1:
The patent transitions from one-dimensional sequential measurement to two-dimensional simultaneous measurement. The optical sensor captures images containing information about thermal expansion in multiple directions (x, y, and z dimensions) at the same time. The processor analyzes these multi-directional displacement fields to calculate CTE values for different orientations, enabling comprehensive characterization of anisotropic materials in a single test.
3Measurement precision
If conventional methods are used, then measurement precision is achieved, but multiple samples with different orientations are required for anisotropic materials
Solution Approach 1:
The patent creates a universal measurement system that can characterize all directional thermal expansion properties of a single test object simultaneously. The optical measurement and digital image correlation analysis can detect thermal expansion in any direction, making the system universally applicable to anisotropic materials without requiring multiple oriented samples. This multi-functional approach eliminates the need for preparing and testing multiple separate samples with different orientations.
4Measurement precision
If conventional methods are used, then measurement precision is achieved, but localized and thermal gradients cannot be tested
Solution Approach 1:
The patent implements local quality measurement by capturing detailed images of specific regions on the test object surface before and after thermal loading. The optical sensor can be positioned to monitor particular areas of interest, and the digital image correlation analysis can calculate thermal expansion characteristics for each local region independently. This enables the system to detect and characterize localized thermal gradients and non-uniform thermal expansion patterns that conventional methods cannot resolve.
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 non-destructive, scalable measurement of thermal characteristics and fiber orientation in materials and structures, addressing the limitations of conventional methods by providing accurate CTE data and detecting defects in a variety of applications, including aerospace and rail transport.
Implementation Method 1
measuring, using an infrared sensor, a change in temperature of the portion of the test object
Implementation Method 2
producing, using an optical sensor, information describing an image of thermal change in displacement of the portion of the test object
Implementation Method 3
imparting, using a laser, laser light on the portion of the test object
Implementation Method 4
imparting, using a laser, laser light on the portion of the test object
Data Source
AI summary
Provided are methods and apparatus for determining a coefficient of thermal expansion (CTE) of at least a portion of a test object. An example provided method includes (i) producing information describing a reference image of the test object portion during low-temperature excitation; (ii) heating the test object portion to a higher temperature; (iii) measuring a change in temperature of the test object portion; (iv) producing information describing an image of thermal change in displacement of the test object portion at the higher temperature; (v) comparing the information describing the image of thermal change in displacement of the test object portion at the higher temperature to the information describing the reference image to produce strain information describing heating-induced changes in strain in the test object portion; and (vi) producing CTE information by correlating the strain information with the change in temperature of the test object portion.