Analysis of temperature treatments and manufacture methods of superelastic niti bending springs with complex-shape

Resumo

The application of smart materials in mechanical systems has been increasing, due to these materials
presenting a capacity to reduce undesirable vibrations with a small increase of mass in the system. The most
applied material is the Shape Memory Alloys (SMA), which change their characteristics with variations in
temperature or mechanical stress. SMAs have two effects: shape memory effect (SME); which changes its phase
with temperature variation, and superelasticity (SE); which modifies its phase with the change in mechanical stress.
For the SMA-SE, properties such as damping capacity and complex stiffness are relevant for application in systems
with undesirable vibrations, principally considering some external parameters such as temperature, frequency, and
amplitude can change the properties of the material. However, if the SMA-SE device has a complex shape, more
procedures are needed to achieve it. Thus, complex-shaped devices tend to be more liable to changes in the starting
properties of the material during the process of obtaining the sought shape, due to the forming process. Therefore,
focusing on obtaining balanced properties, such as damping capacity, complex stiffness, and transformation
temperatures on the SMA-SE devices, several parameters should be considered during the manufacturing, such as
time and temperature of the treatment, cooling speed, and the method of material forming. This paper aims to
evaluate types of heat treatments, application of mechanical forming, and different types of cooling applied in the
manufacture of superelastic NiTi bending springs with complex-shape, to obtain balanced properties for
application in the rotating system to intend to reduce vibration in a passive form.