The two common methods of creating motion from electricity are by motors and solenoids. There is also another very different and much newer way to create motion from electricity byshape memory alloys (SMAs). These special metals undergo changes in shape and hardness when heated or cooled, and do so with great force approximately up to 20 times to their weight.
Among these shape memory alloys, Nitinol is one of the most prominent Shape memory material widely used across different sectors of defense, automotive,aerospace and medical applications.
Nitinol alloy is typically made of 55%-56% Nickel and 44%-45% Titanium. Small changes in composition can significantly impact the properties of the material.With minute changes in Alloy composition, transition temperature of Nnitinol varies from -10°C to 90°C.
Transition temperature is the temperature at which shape memory alloys change their shape on heating or on supply of electricity.
Nitinol wires with transition temperature -10°C to 25°C are called super elastic alloys. 25°C to 40°C are called body temperature alloy and beyond 50°C are called thermal shape memory wires. Super elastic wires are also referred as mechanical shape memory wires.
Heat engine is the common application of SMA. A straightened shape memory Nitinol wire is formed into a loop and by passing it thru baths of cold and hot water, is used to convert heat energy to mechanical energy.
Other applications of SMA wires are automatic green house vents, hot water valves and Fan clutches etc. Nitinol wire can be used as both sensor and actuator at the same time and is used in some coffee makers for sense and activate the temperature.
Most recent innovations include micro robots and ultra small machines with thermally activated Nitinol wires. Robot arm motion is created by contraction of wires.
Shape setting is the procedure used to form Nitinol wire to required shape. Shape setting is done by firmly clamping the wire on fixture or mandrel in required shape and heating it at 550°C for 5 to 10 minutes and quenching it immediately in water or salt bath,also called annealing process.
When cooled, the shape can be easily deformed and when it heated to its transition temperature of 50°C it regains its annealed shape.
Hobbyists and experimenters most frequently use SMAs in wire form, as they can be easily cut and can be activated electrically. Muscle wire is a form of SMA, which contracts on power supply and is designed for precision motion generation like all kind of mechanical movements like linear, triangle and lever motions.
Pseudo/Super-Elasticity describes Nitinol’s ability to dynamically change from austenite to marten site and back again with the application and release of applied stress. This mechanism allows Nitinol to recover much larger amounts of deformation than could be recovered through standard elasticity.
Nitinol has roughly 10 times the deformation recovery capability compared to that of typical stainless steel
Super Elastic Nitinol is typically used in Medical applications like Catheter shafts, Stents, Valve frames. Needles, Orthodontic guide wires, Endoscopic guide tubes, Occluder. Retrievers, Laparo scopes, Orthodontic braces and eyeglasses, Shape Memory Alloys, Mechanical Engineering, Robotics,Mechatronics, Metallurgy & Projects.
Future development of Nitinol Muscle wire involves using multiple wires to create larger and stronger devices. When acting together, groups of muscle wire can exert very large forces. Compact, light and very strong actuators can be built by combining many wires into a single device.
To increase the total force available in a muscle wire powered device, the basic modules would combine groups of wires with force and position sensors, thermal insulation, communication and active cooling systems. Groups of these actuators can create quiet, efficient linear motion without hydraulic or pneumatic pressure sources and massive motor components.
These actuators programmed properly with PLC can be used for android robots, robot limbs and also for artificial limbs.
Nitinol wires are used for build of model rail roads, science fair projects, custom electronic devices, animated models, radio control vehicles, movie special effects, computer controlled systems, ultra small machines and robots.
you can make your unique projects with this fascinating material now from Nitinol wires and other products available at www.vras.in/shop.