Samara Scientists and Students Have Created a Prototype of a Space Hardness Tester

Scientists and students of Samara University has developed and tested a prototype of the compact space hardness tester, a device that can be used to measure hardness of metal directly in outer space in orbit, for example, the coating of the space station or other external structures. Such measurements are needed for assessing the strength of a material: how much the metal degrades over time, “gets tired” in outer space, losing its hardness under the influence of various factors of outer space, such as micrometeorites, cosmic radiation, vacuum, temperature fluctuations.

The Samara development differs from similar “terrestrial” hardness testers in its innovative design, due to which this measuring device is lighter, more compact and energy-efficient. Among the six developers of the tool, there are scientists, engineers, and university undergraduates. The scientific supervisor is Fedor Vasilyevich Grechnikov, Academician of the Russian Academy of Sciences, Professor at Samara University’s Department of Metal Forming. The project has become one of the eight finalists of the competition of innovative projects of the accelerator of the “Energia” Rocket and Space Corporation (RSC).

“Under the influence of the outer space factors, such as high vacuum, radiation, temperature fluctuations, flows of solid microparticles, there is a constant change in the properties of various materials used in spacecrafts, primarily, of course, metals. Temperature deformations and degassing occur, the crystalline structure of the metal changes, resulting in reduced strength, reduced reliability and durability of structures. Therefore, it is very important to monitor the current state, for example, of the coating of space stations. Unfortunately, it is quite problematic to use conventional “terrestrial” hardness testers of the appropriate class in orbit: they are usually heavy, quite bulky and energy-consuming. As part of the project, a prototype demonstration sample of a compact hardness tester was developed and manufactured, which, we believe, is optimally suited for using in space. Compared with devices of the similar class, including those made abroad, our hardness tester has a much smaller mass and dimensions — about ten times; moreover, it is significantly lower energy-consuming. However, the device fully complies with all the requirements of GOST for hardness measurement,” said Fedor Grechnikov, Academician of the Russian Academy of Sciences, Professor at Samara University’s Department of Metal Forming.

There are various methods for measuring hardness and different types of hardness testers, but the principle of operation for most of them is almost the same: some kind of mechanical action is exerted on the surface of the material, the results of which (for example, by the area or depth of the formed dent — an imprint or a scratch) determine the hardness of the tested material. For such an impact on metal, the device, of course, needs the appropriate force. Stationary mechanical hardness testers use a powerful electromechanical drive with the electric motor and the gearbox. However, as a result, the weight of such a hardness tester can be several tens of kilograms, sometimes reaching up to a hundredweight, while the device is quite comparable in size to a hinged kitchen cabinet.

For creating a more compact device, the Samara developers changed its design: instead of the drive with the electric motor and the gearbox, they used a special wire power element made of nitinol (the alloy of nickel and titanium). This special superelastic alloy has “shape memory.” If you make a part out of it, even the most complex shape, and then heat this part to a certain temperature, the alloy will “remember” this shape. If, after cooling, the part is deformed — stretched, flattened, bent, and then, after a while, reheated to a temperature slightly above 40°C, the alloy will “remember” the former shape of the part and accurately restore it, and it will be restored with great force.

The force effect occurs due to restructuring the crystal lattice of the alloy heated. In the Samara hardness tester, the nitinol wire is heated to 80°C in just a few seconds by the current passing through it. However, according the experiments, a wire with a diameter of only 1 mm, when heated, develops a force of up to 50 kg, a wire with a diameter of 1.5 mm — up to 100 kg, and a power element in the form of a nitinol plate with its cross-section of 1x5 mm gives a force of over 200 kg. This force is transferred from the force element to a special “probe” — a tool with a diamond tip that presses on the measured material, and the sensors of the device help determine the hardness of this material. Dimensions of the prototype compact hardness tester are only 150x70x50 mm, the total weight of the device is about 5 kg.

“The prototype hardness tester has already been tested in practice, however, of course, on the Earth, not in outer space. The tests confirmed the operability of the applied innovative solution. In future, such a device can be used to assess the condition of the material in the examined outer points of the space station body, for example, using a robotic arm. Moreover, the hardness tester can be used for creating a test bench that will operate for a long time outside the space station, automatically measuring hardness of new promising materials for spacecraft in outer space. It is simply impossible to conduct such tests of new materials on the Earth, due to the impossibility of simultaneous exposure of the sample to all factors of outer space,” noted Vladimir Glushchenkov, Associate Professor at Samara University’s Department of Metal Forming.

The preliminary design of the test-bench with connection to the space station structure has already been developed. In the future, such a test-bench is possible to work at the Russian Space Station (RSS) being created. The results of testing new materials are planned to be used for developing and operating machines and mechanisms on the Moon and other planets. According to experts, in the long term, such equipment may be useful for studying the properties of metals that are planned to be mined on the Earth’s natural satellite.