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Infrared (IR) contrast analysis and imaging augments and improves flash IR thermography
Researchers at NASA’s Johnson Space Center (JSC) have developed novel techniques for post-processing of flash IR thermography data. These methods efficiently and cost-effectively provide valuable new information when conducting NDE of nonmetallic structural composites during their manufacture as well as over the lifetime of the deployed part. Based on a novel IR contrast approach, this suite of tools is compatible with commercial IR thermography products and provides enhanced imaging, as well as both quantitative and qualitative data analysis capabilities. The methodologies provide reliable detection and characterization of anomalies (e.g., voids, cracks, and areas of delamination) in composite structures made of nonmetallic materials, such as reinforced carbon-carbon and carbon-fiber-reinforced polymers. Characterization capabilities include determining depth, size, location, and boundaries of these flaws. Calibration techniques provide detailed, systematic analysis of flash thermography data comparable to that used in advanced pulse/echo ultrasonic testing, offering performance enhancements not currently available for NDE of composite materials.
- Comprehensive: Includes complementary contrast tools that provide enhanced quantitative and qualitative data about flaws
- Detailed: Offers complementary and predictably accurate insights into defect shape, size, depth, and location
- Competitive: Provides the most precise and detailed characterization of flaws and anomalies in nonmetallic composite structures and thin metallic materials
- Cost-effective: Lowers the cost of implementation through compatibility with existing hardware systems and ability to augment single-sided IR data processing methods
- Accurate: Provides reflection correction and signal processing to improve signal-to-noise ratio, improving flaw detection sensitivity
- Efficient: Extracts and constructs images quickly and simply, saving operators the chore of manually sorting through stacks of images, enabling swifter and more accurate evaluation of thermographic data
- Easy to use: Allows for systematic analysis of flash thermography data in a manner that is similar to pulse/echo ultrasonic testing, making it familiar to technicians
This suite of tools can be applied to NDE using flash IR thermography of any nonmetallic advanced structural composite, such as those used in myriad industries:
- Aircraft fuselage and structure
- Turbine blades
- Power generation
- Turbine blades
- Chemical and petrochemical
- Fuel tanks
- Marine vehicle bodies
- Fuel tanks
- Pressure vessels
- High-performance automotive
- Racecar bodies and structures
Originally used by NASA for NDE of the Space Shuttle Orbiter, JSC’s suite of IR contrast methods and tools enhances mission-critical detection and evaluation of defects in nonmetallic composites using flash IR thermography. This helps ensure the performance, functionality, and safety of composite structures.
How It Works
The standard flash IR thermography setup (see Figure 1) consists of a flashhood, a flash power supply/trigger unit, a flash duration controller, and electronics used to capture the data from the IR camera. It also includes a data display and software for post-processing of the data (see Figure 2). The flashhood helps contain the flash and has one open side, while the other side has a window for the IR camera lens. The camera is mounted to the outside of the hood, and flash lamps direct the illumination toward the hood opening.
This setup houses the material being evaluated and directs a pulse of IR light onto it. The material’s reflected thermal response generates an IR image. When a defect is present, heat flowing at the structure’s front surface is impeded relative to the surrounding defect-free areas. Variations in the thermal diffusivity of the material manifest themselves as anomalies in the IR image of the test surface (see Figure 3).
JSC’s innovative IR contrast analysis and imaging methods post-process the IR camera data, evaluating any detected anomalies by using the evolution of measured pixel intensity over time compared with a calibrated empirical simulation.
This post-processing of the raw IR camera data provides highly detailed analysis of the size and characterization of anomalies, including both quantitative and qualitative information. Complementary contrast tools (see Figure 4) offer highly precise measurements:
- The peak contrast and peak contrast time profiles provide quantitative interpretation of the images, including detailed information about the size and shape of the anomalies.
- The persistence energy and persistence time profiles provide highly sensitive data giving indications of the worst areas of the detected anomalies.
- Peak contrast, peak time, persistence time, and persistence energy measurements also enable monitoring for flaw growth and signal response to flaw size analysis.
- The normalized temperature contrast profile provides more sensitive response than image contrast, allowing the system to detect smaller flaws.
Why It Is Better
Although optimized for performance, critical components in aerospace structures can be difficult, if not impossible, to inspect adequately due to design complexity and/or the use of advanced materials. JSC’s suite of software and tools offers a cost-effective and efficient way to provide more comprehensive, detailed, and accurate NDE detection and characterization of subsurface defects in nonmetallic composite materials having flat or curved surfaces.
Currently available commercial thermography software does not use image contrast or temperature contrast and therefore provides less accurate characterization of defects. Furthermore, because this software normalizes and calibrates data, it provides more stable measurements and greatly minimizes errors due to operator and camera variability.
NASA has received one patent for this suite of technologies (U.S. Patent No. 8,577,120) and has a second patent pending.
This suite of technologies is being made available through JSC’s Technology Transfer and Commercialization Office, which seeks to transfer technology into and out of NASA to benefit the space program and U.S. industry. NASA invites companies to consider licensing the flash IR thermography suite of software and tools (MSC-24444-1 and MSC-24506-1) for commercial applications.
Technology Transfer and Commercialization Office
NASA's Johnson Space Center