Thermographic Nondestructive Evaluation of Porosity and Diffusivity
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Solution Overview
Problem
Existing nondestructive testing methods, such as ultrasonic measurements, are cumbersome, time-consuming, and impractical for large or complex objects, while infrared transient thermography is faster but requires thickness information and is affected by surface emissivity variations and reflections.
Innovation Solution
A method using thermal time of flight analysis to determine thermal diffusivity and porosity without requiring exact thickness information, using a heat source and a focal plane array camera to capture lateral heat flow images, and applying time of flight analysis to determine diffusivity and porosity values independently of surface emissivity and reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic measurements are used to determine cross-sectional thickness, then measurement precision is improved, but testing time and device complexity increase significantly
Solution Approach 1:
The patent replaces the mechanical ultrasonic scanning system with an infrared thermographic system. Instead of using mechanical scanning and acoustic waves, the method uses infrared radiation to detect thermal patterns caused by heat transfer through the material, thereby reducing testing time while maintaining measurement capability.
Solution Approach 2:
The patent changes the measurement parameter from acoustic wave reflection time (ultrasonic method) to infrared thermal pattern analysis (thermographic method). By measuring thermal diffusion patterns instead of acoustic echo times, the system achieves rapid non-contact measurement without requiring mechanical scanning.
2Measurement precision
If ultrasonic measurements are performed on large objects, then measurement precision is maintained, but device complexity and operational difficulty increase
Solution Approach 1:
The patent eliminates the complex mechanical scanning system by using non-contact infrared thermography. The infrared camera captures thermal patterns across the entire surface simultaneously without mechanical movement, greatly simplifying the device while maintaining measurement precision for large objects.
Solution Approach 2:
The patent transitions from point-by-point mechanical scanning (1D/2D traversal) to area-wide simultaneous capture (2D/3D imaging). By using infrared cameras to capture thermal patterns across the entire surface at once, the system reduces device complexity while maintaining comprehensive measurement capability.
3Productivity
If infrared transient thermography is used to determine diffusivity, then productivity is improved, but measurement precision deteriorates due to surface emissivity variations and reflections
Solution Approach 1:
The patent addresses the harmful effect of surface emissivity variations and reflections by using a differential measurement approach. Instead of measuring absolute temperature values (which are affected by surface properties), the system measures temperature changes over time and spatial patterns, converting the surface property variations from a source of error into a non-interfering factor that cancels out in the analysis.
Solution Approach 2:
The patent introduces thermal diffusion patterns as an intermediary that mediates between the heat source and the measurement. By analyzing how heat spreads through the material over time, the system creates a measurement pathway that is independent of surface emissivity properties, using the material's thermal properties as the true signal carrier.
4Measurement precision
If conventional infrared thermography requires thickness information for calibration, then measurement precision is maintained, but device complexity and operational difficulty increase
Solution Approach 1:
The patent enables the system to be self-calibrating by using the material's own thermal response to the heat source as the measurement basis. The thermal diffusion patterns captured by the infrared camera inherently contain the diffusivity information, eliminating the need for external calibration standards or prior thickness information, thereby reducing device complexity.
Solution Approach 2:
The patent extracts the diffusivity measurement capability from the calibration process. By using non-contact infrared thermography with thermal pattern analysis, the system extracts thermal diffusivity information directly from the material's thermal response without requiring separate calibration measurements or thickness inputs, separating the measurement function from calibration requirements.
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 rapid, non-destructive evaluation of porosity and diffusivity in composite materials without needing thickness information, eliminating the need for calibration and curve fitting, and is unaffected by surface emissivity variations or reflections, providing reliable diffusivity and porosity measurements.
Implementation Method 1
heating a surface of the article; capturing image data corresponding to an evolution of lateral heat flow from the surface
Implementation Method 2
a focal plane array camera configured to capture a plurality of images corresponding to an evolution of lateral heat flow
Implementation Method 3
applying a thermal time of flight analysis on the image data; determining thermal diffusivity and porosity values
Data Source
AI summary
A method and system for determining thermal diffusivity and porosity of an article are provided. The method comprises heating a surface of the article, capturing image data corresponding to an evolution of lateral heat flow from the surface of the article, applying a thermal time of flight analysis on the image data and determining thermal diffusivity and porosity values of the article using the thermal time of flight analysis for the lateral heat flow.