Nitinol (NiTi)
Never heard of it? Ninitol the name of a Nickel-Titanium alloy in approx 50-50 composition.
The world hardly uses any nitinol at all, because itβs kinda expensive, and itβs because of process chemistry, but itβs a super interesting engineering material with incredible properties.
Hereβs why we should use it moreβ¦
It has a combination of steelβs strength but has super elasticity up to 8% elongation in its stress/strain curve, this means it can bend, stretch and twist a lot and then still return to its original shape.
It has shape memory.
This makes it super compliant in assemblies, reducing demands of precision.
Often⦠A single Ninitol spacer can soak up all your tolerance stack ups, and save you $$$ of precision machining cost (see the curve below).
Few mechanical designers have any experience with super elastics metals, but think of gaskets and seals, springs, cages, clutches, torque limiters, the list is long.
Shape memory is the ability of nitinol to undergo deformation, stay in its deformed shape when the external force is removed, and then recover its original undeformed shape when you heat it above its transformation temperature.
Superelasticity is the ability for the metal to undergo large deformations and immediately return to its undeformed shape upon removal of the external load. Nitinol can undergo elastic deformations 10 to 30 times larger than alternative metals.
Ninitol has both of these unusual behaviours.
Whether nitinol behaves with shape memory effect or superelasticity depends on whether it is above its transformation temperature during the action.
You can tailor the transformation temperature from -20Β°C to 110Β°C (-4Β°F to 230Β°F).
Itβs highly biocompatible, and you can put the transformation temperature in human bodyheat range.
There are lots of clever design uses of these two behaviours and almost zero real world examples.
Ninitol is vastly unexploited, the global economy use 5,000 tonnes / year. We should be using 200x that amount.
Self regulating thermal control, heat harvesting, mechanical compliance, there are huge problems that are ignorant of existing material solutions.
I find it puzzling that robotics companies arenβt building ninitol actuators. Itβs practically a sort of metallic muscle tissue if you cut a mesh and twist it round a mandrel.
It should be a foundational smart material that we should be exploiting by now. 5kT/yr is pitiful.