Flexible Pixel Heater for Thermographic Inspection
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Solution Overview
Problem
Conventional thermographic inspection systems using optical excitation face limitations with objects having high reflectivity and low transmissivity, as well as complex shapes and curvatures, due to insufficient heat penetration and environmental interference.
Innovation Solution
A thermographic inspection system employing a flexible, sheet-configured pixel heater with independently controllable resistive heating elements for direct thermal conduction to the object's surface, allowing precise heat application and improved heat propagation, regardless of surface geometry or environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical excitation (flash lamp) is used for thermographic inspection, then the system can detect defects through thermal wave propagation, but objects with high reflectivity and low transmissivity reflect light away and prevent sufficient heat penetration
Solution Approach 1:
The patent replaces optical excitation (flash lamp) with direct contact heating elements that conduct heat thermally into the object. This substitution eliminates the problem of light reflection by using thermal conduction instead of optical radiation, allowing effective heat penetration regardless of the object's optical properties.
Solution Approach 2:
The patent introduces a coupling medium or direct contact heating element as an intermediary between the heat source and the object surface. This intermediary ensures efficient thermal conduction into the object, overcoming the barrier created by high reflectivity surfaces that would otherwise prevent heat penetration.
2Measurement precision
If optical excitation is used for thermographic inspection, then defect detection is possible, but environmental reflections and complex surface geometry interfere with the inspection
Solution Approach 1:
The patent replaces optical excitation with direct contact heating, which eliminates environmental reflections from affecting the inspection. By using thermal conduction through direct contact, the system becomes immune to optical interference from the environment and complex surface geometries.
Solution Approach 2:
The patent extracts the heating function from the optical excitation system and implements it separately through dedicated heating elements in direct contact with the object. This separation removes the harmful environmental reflections associated with optical methods while retaining the thermal wave propagation needed for defect detection.
3Temperature
If flash lamp optical excitation is used, then thermal waves can be induced in the object, but insufficient heat is transformed and entered into the object to create visible temperature differences
Solution Approach 1:
The patent replaces optical energy transformation with direct thermal conduction. Instead of relying on the flash lamp to convert optical energy to heat at the object surface (which is inefficient for high reflectivity materials), the system uses heating elements that directly conduct thermal energy into the object, dramatically improving heat transformation efficiency.
Solution Approach 2:
The patent introduces a thermal coupling intermediary (heating element in direct contact) that efficiently transfers thermal energy from the heat source into the object. This intermediary ensures maximum heat transformation efficiency by eliminating the optical reflection barrier that plagues flash lamp methods.
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
Enhances heat penetration and detection accuracy by enabling effective thermal wave propagation through direct contact, facilitating inspection of complex shapes and reducing environmental interference, while allowing for controlled heat application and improved defect detection.
Implementation Method 1
The pixel heater (12) includes a plurality of independently controllable resistive heating elements (42)
Implementation Method 2
The plurality of resistive heating elements (42) being in direct contact with an exterior surface (28) of the object (26) to be examined, allowing heat to be conducted directly into the object
Implementation Method 3
An infrared camera may be used to capture the thermal image, and namely the thermal pattern on the exterior surface
Data Source
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Figure 3
AI summary
An infrared thermographic inspection system (10) includes a heat source (12) configured to be removably attached to an exterior surface (28) of an object (26). A thermal imaging device (16) obtains a thermal image of the object (26), and an analyzing device (20) determines a location of a defect (24) in the object (26) based on the thermal image. The heat source (12) consists of a flexible polyimide heater (12) comprising a plurality of heating elements (42) which are independently controlled and the flexible heater can conform to the exterior surface (28) of the object (26).