Shape memory alloy is an alloy that can automatically restore its own plastic deformation to its original shape at a certain temperature.
In addition to its unique shape memory function, memory alloys also have excellent characteristics such as wear resistance, corrosion resistance, Gaozuni and hyperelasticity.
The telescopic rate is more than 20 %. The fatigue life reaches 107 times, the damping characteristic is 10 times higher than the ordinary spring, and its corrosion resistance is excellent.
The best medical stainless steel at present, so it can meet the needs of various engineering and medical applications, is a very excellent
Functional material.
Production can be used for glasses legs, women's bras, mobile phone antennas,
High Quality Memory in Women's Nursery Ring, Tooth Bow Silk, Instrument, etc..
Alloy.
In 1963, the US Naval Ordnance Research Office needed some nickel-titanium alloy wire in an experiment. The alloy wire they brought back was curved. For ease of use, these twisted filaments are straightened and used root by root.
In the follow-up experiment, a strange phenomenon occurred: when the temperature rose to a certain value, these alloy wires, which had been pulled straight, suddenly and magically quickly returned to the original curved shape, and it was not inferior to the original shape. Again and again, the results are exactly the same each time. As long as the straight alloy wire reaches a certain temperature, it immediately returns to the original curved appearance.
It was as if they had been changed by people when they had been "frozen" and lost consciousness. When the temperature rose to a certain value, they suddenly "awakened" and "remembered" themselves. So he desperately restored his "true face."
The crystal structures of nickel-titanium alloys above 40oC and below 40oC are different, but when the temperature changes above 40oC, the alloy contracts or expands, causing its morphology to change.
Here, 40oC is the "abnormal temperature" of the nickel-titanium memory alloy. All kinds of alloys have their own abnormal temperatures.
Memory alloys have been used for pipe binding and automated control. The use of memory alloys to make casings can replace welding by fully expanding the end of the pipe at low temperatures. When assembled, they are put together. Once heated, the casings shrink to restore the original shape. To form a tight joint.
The United States Navy aircraft's hydraulic system uses 100,000 such connections and has not experienced oil spills or damage for many years. Ship and undersea oil field pipeline damage, with memory alloy accessories repaired, very convenient. In some inconvenient parts of construction, pins are made of memory alloys and heated in holes. The tail ends are automatically curled separately to form single-sided fittings.
Memory alloys are particularly suitable for thermal machinery and thermothermal automatic control. They have been made into room temperature automatic open and closed arms, can open ventilation Windows during the sunlit day, and automatically close when room temperature drops at night.
There are also many design solutions for memory alloy heat engines. They can work between two media with low temperature difference, thus opening new ways to use industrial cooling water, nuclear reactor heat, ocean temperature difference and solar energy. The prevailing problem is that the efficiency is not high, only 4 to 6, and it needs to be further improved.
The medical application of memory alloys is also very noticeable.
For example, bone plates used for grafting can not only fix two broken bones, but also generate compression force in the process of restoring the original shape, forcing the broken bones to join together. Orthodontic filaments used in dentistry, long clips for ligation of brain aneurysms and vasectomy, and branch plates for spinal straightening are all initiated by the effect of body temperature after implantation in the human body. The thrombus filter is also a new memory alloy product. After the straight filter is implanted into the vein, it gradually returns to the mesh, preventing the 95-inch clotting block from flowing to the heart and lungs.
The artificial heart is a more complex organ. The muscle fibers made of memory alloys are combined with the elastic thin film ventricle and can imitate the ventricular contraction movement. Now the pump has been successful.
Since memory alloys are "living alloys", the use of their shape at a certain temperature can be used to design a variety of self-control devices. Its use is constantly expanding.