# Experimental Analysis on the Impact of Current on the Strength and Lifespan of a Ni-Ti Element
## 5 Conclusions  
The test stand was used to test and evaluate the characteristics of smart materials, to understand how they respond to various thermal stimuli and how they can be used in the development of technical eq/uipment based on Ni-Ti with nitinol. Tests performed in the research laboratory found that Joule heating of the active elements by applying an electric current to its terminals is more efficient than heating using external sources. The elastic systems have been tested individually, and the application is intended to analyze the response to fatigue resistance. In the tests, a comparison was made applying two different stimulation currents in order to evaluate the use of active elements for the development of applications based on electric current control. The first variant, on which an \(\mathrm{I}_{1}\) current of approximately 50% of the maximum current tested in the laboratory was applied, which can damage the element, demonstrates that after a very large number of cycles repeated continuously for 19 days of operation, under the same conditions, it retains the elastic characteristics and can therefore be used in the industrial field, but also in medicine and in the automotive industry. The second test shows that when applying an \(\mathrm{I}_{2}\) current, at 85% of the maximum current, which can damage the active element, even if initially a high performance is achieved on the generated force and more precise control of the element with a reduced time constant, it it permanently loses the properties of shape memory, which decreases its lifespan by applying a higher current, elastic performance, shape and making it impossible to be reused. For the best possible analysis of Ni-Ti samples, the factors that can substantially influence their accuracy must be taken into account: the temperature of the external environment, the air flows around the active elements, the temperature at which the alloy is activated, the overall size necessary to control them. Figure 8: Ni-Ti spring after testing phase with \(\mathrm{I}_{1}\) current (**a**) and after testing phase \(\mathrm{I}_{2}\) current (**b**). Figure 7: The force variation generated by the Ni-Ti during the test period (5 days of continuous operation) at the applied electric current, \(\mathrm{I}_{2}\). The transient regime of the nitinol spring element is influenced by the ambient temperature and the small construction errors of the test stand. In order to reduce these disadvantages, a thermal insulation of the tested element and a high accuracy of the measurements regarding its movement over time can be achieved. Following the testing of nitinol elements of several types and shapes, under different conditions and through the development of applications in the Laboratory of Invention and Technology Transfer of the Stefan cel Mare University of Suceava, several aspects were highlighted regarding the behavior of the material with shape memory, namely behavior such as having a non-linear characteristic in operation, which are strongly influenced by ambient temperature and air currents. The transition temperature point is a very important aspect in choosing the alloy for various applications; it can be easily controlled by supplying it to a voltage source, with the possibility of generating the necessary force depending on the applied electric current. Additionally, it is in the form of springs and straight wire, and it is necessary to store it in certain shapes as needed; the storage methods are complex, requiring constant high temperatures and requiring the storage form to be maintained. The cycles have to be repeated several times until it is set to the desired shape. Additionally, systems that use drives using shape memory materials have high reliability, simplicity of construction and advantages in terms of size and mass, allowing many applications to be developed, the fields of application ranging from the toy industry, the energy industry, automation, the automotive industry and the aerospace industry to the field of medical engineering.