Nickel‐titanium Wires in Tension Test
High‐resolution high‐speed thermography with ImageIR® 9300
How do solid materials change structurally? The engineers Prof. Stefan
Seelecke and Marvin Schmidt from Saarland University investigate thisfundamental question in materials research. Both consider this topic with thehelp of microthermography. Their cutting‐edge basic research ensures that wewill have even more energy‐efficient electric devices to use at home in future.

Saarland University
Zentrum für Mechatronik u.
Automatisierungstechnik
www.zema.deInfraTec solution:ImageIR® 9300

In the last few decades, researchers have worked increasingly on alternative cooling technologies that do not use
refrigerants containing fluorocarbons. Technologies such as ferroelastic cooling promise high effectiveness, a more
efficient use of resources and reduction of greenhouse gas emissions. This form of cooling uses wires of a pseudo‐
elastic shape memory alloy based on nickel/titanium (NiTi). A mechanical load on the NiTi wires causes large,
reversible deformations due to a stress‐induced martensitic transformation. A martensitic structure is created, andthermal energy is given off to the surroundings. With removal of the load, the stress‐induced martensitic structurechanges back into the original austenite. Thermal energy from the surroundings must be expended for this.
To achieve the maximum savings potential of ferroelastic cooling, the entire deformation process must be regulatedoptimally. The researchers want to control parameters independently, such as frequency or phase shift between themechanical stress and heat transfer. In addition, they want to measure the resulting cooling performance for a specificmaterial and a specific device geometry. To do this, Seelecke and Schmidt have developed an imaging measurement
platform.
It works with an ImageIR® 9300. The high‐end thermal imaging
camera is equipped with a 1x microscope lens and detects thewire to be measured, whose diameter is only approximately
150 µm. Exact thermographic temperature measurement even on longer
wire sections is ensured through the geometric resolution of 15 µm. In thisway, the researchers can retrace the ferroelastic cooling
effects very precisely. Thanks to the camera's (1,280 x 1,024)
IR‐pixel detector, the Saarbrücken‐based scientists canmonitor long parts of the tiny wire and record the structuralchanges. The high temporal resolution of the ImageIR® 9300 ofup to 106 Hz in full‐frame format also lets them follow evenbrief temperature changes.
The images clearly show how a NiTi wire heats up throughstretching and cools off when relaxed.

Evaluation of the thermograms is just as sophisticated. Reflection effects and emission coefficients that arecomplicated to determine are among the regular challenges. Seelecke and his team therefore value the integrated
correction model of the supplied IRBIS® 3. “With the software we can compensate for astonishingly many effects. Thatclearly makes our work easier.” The software, together with the large detector format and the high geometric,
thermal and temporal resolution, forms a package that makes the ImageIR® 9300 ideally qualified for use in materials
research. And by the way, this combination will hopefully do its part to ensure that we all can save more energy andprotect the environment in the foreseeable future.

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