Scientists from the Institute of Problems Mechanical Engineering (IPMash) of the Russian Academy of Sciences, together with colleagues from St. Petersburg State University for the first time have created a model that makes it possible to predict accurately how the shape memory alloys will protect structures from destructive vibrations and seismic impacts.
These unique materials, which are able to «remember» their shape, change their properties depending on the temperature and speed of the load. The results of the study are published in Smart Structures and Systems.
Shape memory alloys (SMA) are unique materials capable of «remembering» their original shape and returning to it after deformation. Due to this property, they are used in systems which protect buildings, bridges and industrial structures against vibrations and earthquakes.
SMA effectively dampen vibrations, reducing the destructive effects of loads, and at the same time have a high durability. The properties of these alloys depend on temperature: when heated and cooled, they change their structure, becoming either more rigid or more flexible.
This allows you to customize them for different tasks. For example, in one mode they can absorb vibration energy (damping), and in the other they can simply deflect vibrations without passing them further (isolation). This flexibility makes them ideal for protecting mission-critical facilities.The use of SMA opens up new opportunities in construction and mechanical engineering.
These materials can adapt automatically to changing loads, increasing the reliability of structures. For example, in earthquake-prone regions, buildings with SMA elements will be more resistant to earth shokes, and industrial equipment will suffer less from vibrations.

“In the published work, a one–dimensional oscillatory system, a torsional pendulum, was modeled, taking into account the influence of key factors on the temperature of the working medium: ambient temperature, heat exchange and loading rate. Experiments were modeled to identify the influence of each of the factors on the effectiveness of the vibration protection device,” said Fedor Belyaev, IPMash RAS senior researcher at.

The scientist notes that these factors influence strongly the SMA and without them it is impossible to describe accurately and simulate the operation of vibration-proof devices.

During the experiments, it turned out that these materials behave differently depending on the heating and cooling conditions. When the alloy is deformed slowly at a constant temperature (for example, under normal room conditions), and when it is done quickly (so that the heat does not have time to leave), the difference in heating can reach 20 degrees. With rapid exposure, the material becomes noticeably tougher. How exactly the alloy cools is of great importance.
If it simply cools down in the air, its behavior is close to the adiabatic case when there is no heat transfer. But if you expose it to water cooling, the heat exchange rate increases, and the ability to dampen vibrations improves significantly. It is also important to take into account the speed of impact: with sharp impacts, the material copes with vibration worse, but if it is cooled down a little beforehand, this problem disappears.

Two approaches have shown the best results in controlled vibration protection systems.

The first is to cool the alloy quickly, forcing it to enter a low-temperature phase with high damping capabilities. The second is to heat the material abruptly first before it enters the high-temperature phase, and then cool it to its initial state.

“As a result, we can say that we have developed a SMA mechanical model, which can be used in the design of new, more effective vibration and seismic protection devices. Due to the consideration of thermal processes, the model allows to obtain more accurate results, which will allow the developers to choose more suitable alloys and their operating modes. In addition, the model allows us to develop semi-active vibration protection systems and programs for their control,” said Fedor Belyaev.