Nitinol - Shape Memory Alloy: Introduction

Nitinol belongs to a type of material called shape memory alloy (SMA). SMA has interesting mechanical properties. Flexynol is the trade name of a nitinol actuator wire trained to contract upon heating, as opposed to the expansion of the standard metal upon heating. This alloy not only shrinks but is 100 times bigger than the thermal motion of the standard metal (expansion - contraction).

Another interesting feature of SMA is what is called shape memory effect (SME). Alloys can be stored for specific shapes. Once the shape is memorized, the alloy will bend or deform. After that, the original shape is restored by heating the alloy transition temperature. This SME attribute is for toys called Nitinol Memory Wire. See figure

You can bend the Nitinol Memory Wire toy in whatever form you want, then put it in hot water and immediately change its shape into a shape. Interestingly, looking at this wire spreads almost magically and returns to its original shape. Nitinol memory toy is made of nitinol wire, transition temperature (hot water temperature) is low. The force generated when the wire is repaired is very strong. Nitinol material of 1 square inch creates return force of shape of + 30,000 PSI

Nitinol alloys have two closely related unique properties of shape memory effect (SME) and superelasticity (SE; pseudoelasticity, also known as PE). Shape memory is the ability to restore the original undeformed shape when Nitinol deforms at a certain temperature and is heated beyond its "transition temperature". The superelasticity takes place in a narrow temperature range just above its transition temperature, in this case there is no need to heat it to recover the undeformed shape, the material shows 10 to 30 times more elasticity than the usual metal .

Features of NiTi or Nitinol include shape memory effect, super elasticity and high damping capacity. By changing composition, machining and heat treatment these technical properties of the NiTi shape memory alloys can be changed drastically to suit Johnson Matthey's specific customer application. In the nickel-titanium shape memory alloy of Johnson Matthey Medical Components Components, the temperature of the SMA memory of its high temperature form can be adjusted by heat treatment, the composition of the alloy varies from 0 ° C to + 105 ° C. Shape recovery occurs within a few degrees, and start / end points of shape recovery can be controlled within a few degrees Celsius