Future applications of Ni-Ti alloys in automotive safety systems

The shape memory alloys present unusual thermo-mechanical properties. The most important of them are pseudo-elasticity and memory effect. The paper investigates this behaviour for the Ni-Ti wires under static (v < 50 mm/s) and dynamic conditions (v > 50 mm/s) at different temperatures. Ni-Ti actuator and pseudoelastic wires with diameter between 0.1 mm to 0.5 mm are being tested. For dynamic investigation a new testing plant able to satisfy the testing conditions is created. This new testing plant is still under development and the reported results originate from the first tests on this new machine. The new device is designed to reach speeds higher than 50 mm/s. These speeds can be achieved using a drop weight which will hit a bottom plate and by this the kinetic energy is transferred to the sample. Because the weight is dropped, the stroke for the sample is measured in two points. The force of this impact will be in-line measured and, if the sample will be electrically activated during this test, it is also possible to log the electrical voltage. To widen the application range of the shape memory alloys it is necessary to study their behaviour in the dynamic region. With the new testing facility, it is expected to test the damping properties of SMA wires. In that case, these results can generate the basis for finding new applications for shape memory alloys especially in the automotive safety industry.