High-Temperature, Imaging-Based Strain and Temperature Measurement Method for Ground Testing Hypersonic Structures

Completed TRL 4 (started at 3, targeting 4)

Description

This technology is ultimately the simultaneous application of two techniques which will be used to collect two data sets that will be fused together to calculate a third quantity, mechanical strain, by accounting for the thermal component of strain. The first technique, high-temperature thermography, has been a mature field for decades [13]. The second technique, high-temperature Digital Image Correlation for strain measurements, is a relatively young technology and many of the applications only apply in very special conditions. Some examples include: 2D conditions on a coupon test article, in a vacuum or in a furnace, or possibly heated by induction coils or joule heating via direct current through the coupon, as opposed to Infrared radiation heating from lamps [2,3,4,5,8,9,10,11]. These special conditions lend themselves conveniently to testing coupons in 2D. This is very limiting. Substructures used on hypersonic vehicles are more complex as they are three dimensional, can be composed of multiple parts, and the only practical heating method that simulates hypersonic conditions is radiative heating via infrared lamps--typically quartz lamps. There has been one attempt that I’m aware of to combine the two measurement techniques, but the research’s method was not capable of collocating the measurements, and therefore could not separate mechanical strain from thermal strain [6]. GOM, a company that produces Digital Image Correlation systems, claims to have solved the colocation problem with their software. However, they are unable to provide evidence that their system can work at elevated temperatures. So, many pieces of the puzzle have been solved individually, but so far none have combined all the solutions and applied them simultaneously to solve the entire problem.
Below is a bibliography that summarizes the literature that I have reviewed that is related to this problem and an imaging-based solution.

Benefits

This innovation will fulfill unmeet ground testing requirements and proved a better solution to existing ground testing needs. Specifically, customers would like to ground test aerostructures at extreme temperatures, measure the surface temperature, mechanical strain, and thermal strain. However modern strain gage and fiber optics techniques fail prematurely due to complications at elevated temperatures. This novel imaging-based technique will permit the simultaneous measurement of strain and temperature up to (but not limited to) 1,200°C. The temperature and strain measurements will be collocated, meaning that the strain measurement and temperature measurement will be made at effectively the same location. This permits one to use the temperature measurement to separate out the mechanical strain from the thermal strain, which is highly valuable for model validation. Additionally, because the technique is imaging-based (that is, it uses cameras to make both the strain and temperature measurements) the measurement spatial resolution is tied to the resolution of the cameras used. This results in significantly higher spatial resolution of both the temperature and strain measurements, roughly at least two orders of magnitude higher, possibly three. Future increases in infrared camera resolution and digital camera resolution would continue to grow the utility of this technology. Finally, this technique would permit measurements in small corners where traditional techniques are unable to reach because of their large footprint.

Details

Technology area	Materials, Structures, Mechanical Systems, and Manufacturing
Program	Center Innovation Fund: AFRC CIF (AFRC CIF)
Lead organization	Armstrong Flight Research Center, Edwards, CA
Start date	2020-10-01
End date	2021-09-30

Project contacts

Listed on TechPort itself — the most direct way to ask about this specific project.

Erick R Rossi De La Fuente — erick.r.rossidelafuente@nasa.gov

How to get involved

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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