Nitinol shape memory material is a special material that integrates sensing and driving. Nitinol shape memory alloy is an important part of Nitinol shape memory material. Nickel-titanium shape memory alloy is an alloy that undergoes low-temperature plastic deformation and changes its shape to another shape in a certain initial state. The temperature is increased by means such as heating and then changed to the original shape.

Characteristics of Ni-Ti shape memory alloy

(1) Shape memory

After a certain heat treatment, the shape of the nickel-titanium shape memory alloy can be restored automatically. This change is the shape memory characteristic of NiTi shape memory alloy. Shape memory can be divided into one-way shape memory, two-way shape memory and overall shape memory according to the recovery state.

(2) Super elastic

The superelasticity of NiTi shape memory alloy is that under the action of external force, NiTi shape memory alloy deforms. After the external force is eliminated, the superelasticity of NiTi shape memory alloy returns to its original state. The superelastic deformation of NiTi shape memory alloy will directly cause the martensite transformation, and the reverse martensite transformation will occur when the external force is eliminated.

(3) Damping

NiTi shape memory alloy (SMAS) has very good damping performance, which is due to the self-adjustment of the phase transition and the interface and motion generated during the phase transition.

(4) Resistance

Martensitic nickel-titanium shape memory alloy has a linear relationship between resistance and strain during deformation. When the transformation occurs, the slope of the curve decreases, but the linear relationship is maintained before and after the martensitic transformation.

two. The role of NiTi shape memory alloy

Nickel-titanium shape memory alloy (SMAS) has been widely used in many fields due to its unique functions, superelasticity, wear resistance and corrosion resistance.

(1) Mechanical engineering

Nickel-Titanium Shape Memory Alloy (SMAS) was first used in the mechanical industry of pipe joints and fasteners. Specifically, at the joints of mechanical parts, pipes, etc., when refueling in the air, Niti shape memory alloy is used to process the casing with an outer diameter 3% larger than the inner diameter. At a certain temperature, the expansion rate of the casing is about 8 %. During assembly, remove the case from liquid nitrogen and insert it from both ends. If the temperature rises to normal, it can be changed by electric heating. The filler neck Ni-Ti alloy shape memory alloy is deformed, and the casing processed by Ni-Ti alloy shape-memory alloy shrinks to form a tight seal, which achieves a tight oil leakage, which is much better than traditional welding. Therefore, nickel-titanium shape memory alloy is particularly suitable for aerospace, marine, oil pipeline and other fields. Where construction is inconvenient, the pins can be made of nickel-titanium shape memory alloy and heated inside the holes. Therefore, nickel-titanium shape memory alloys are used to drive various functions to make robots and manipulators.

(2) Construction industry

As described above, the nickel-titanium shape memory alloy has various characteristics. Combined with the structure of Ni-Ti alloy shape memory alloy, the system's damping can be improved, and the dynamic response of the structure can be reduced, thereby producing various types of damping energy dissipation devices. Vibration isolators can also be designed with nickel-titanium shape memory alloys. Deformation of the Ni-Ti shape memory alloy can increase the energy dissipation of deformation displacement, prevent the transmission of seismic energy to the upper structure, thereby protecting the superstructure and truly improving the seismic performance of the structure.

(3) Aerospace industry

In aircraft hydraulic systems, almost every aircraft requires 800 nitinol shape memory alloy joints. Since the 1970s, most naval aircraft in the United States have used this fitting, and there is no fault record. In addition, NiTi shape memory alloys can also be used in spacecraft antennas, electromechanical actuators, and so on.

(4) Automotive Industry

Nitinol shape memory alloys are mainly used in engine exhaust fan clutches, exhaust nozzles, diesel engine radiators, etc.

(5) Medical field

Nickel-titanium shape memory alloy has high mechanical properties and biocompatibility, and has been widely used in the medical field. Such as orthodontics, surgery, cardiovascular minimally invasive, etc .; thrombus filters are actually new products of nickel-titanium shape memory alloys; corrected filters gradually form a network with the implantation time.