Shape memory alloys
A collection of resources to support teaching students about shape memory alloys.
Using shape memory alloys
A Catalyst article describing the use of smart materials to help people with disabilities. Many more people with physical and mental disabilities are leading independent lives at home, thanks in part to recent technological developments. The article focuses on one project which makes use of smart materials to help people with dementia.
Shape Memory Alloys
This film clip shows some of the latest ideas for aeroplanes being trialled by NASA. Amongst the concepts are wings which change shape while in the air to make the aeroplane faster and more fuel efficient. This is only possible due to a remarkable range of smart materials. One of the materials being used is a nickel titanium shape memory alloy. It can be bent and twisted like ordinary steel wire, but when an electric current or heat is used to raise it above its threshold temperature it enters a super elastic state and returns to its original shape. When the wire is coiled into a spring, it can be used to generate a pulling force. Known as muscle wire, this is increasingly being used in low cost actuators and switches.
Two Way Memory Spring
This short film from the Technology Enhancement Programme (TEP) is one of a series of clips which were produced to demonstrate the properties and use of a range of smart materials.
These springs, based on a brass alloy, ‘remember’ to open up at around 90°C and close again when cool. Such springs have many industrial applications, such as in sprinkler and fire damping systems where they replace expensive single-use only fusible links. Memory springs open and close with considerable force and are used in countless applications where movement is wanted at the opening and closure threshold temperatures.
Metals and Smart Alloys
This booklet produced by the Science Enhancement Programme (SEP) is mainly aimed at Key Stage 4 but can be used as an introduction to Memory Shape Alloys. The following two activities can be used to model the way in which the latest ‘smart’ or ‘shape memory’ alloys work and introduces some of their applications.
Activity B1 page 36 shows a good way of introducing the principles of the shape memory effect using a model of a robotic arm. The model uses two pieces of thin smart wire connected to a lever on either side of a pivot. When a battery is connected to one of the smart wires, the wire contracts (by about 5%) and the lever moves. If the battery is disconnected, and current is now passed through the other wire, the lever moves back in the opposite direction. When a smart wire is used like this it is also called muscle wire.
Activity B5 page 41 demonstrates how the principles of training a smart alloy can be explored quite simply using a piece of memory wire. Training a sample of a smart alloy generally involves a complex process of treatment over a number of cycles in which it is deformed, heated and cooled.