The strain brain

A wireless ‘nervous system’ for measuring stress could be used to prolong the life of anything from vehicle suspension systems to bridges, oil rigs and artillery equipment.

A wireless ‘nervous system’ for measuring stress could be used to prolong the life of anything from vehicle suspension systems to bridges, oil rigs and artillery equipment says its UK developer.

The structural integrity monitor, being developed by University College London spin-out Fiostec, is based on an electrical resistance strain gauge.

Strain alters the electrical properties of the sensor, allowing the device to measure and record the information. But unlike existing strain gauge equipment it is self-contained, carrying out all the measurement and analysis locally.

This makes the device much more robust, and means it is not prone to interference caused by sending information down long lengths of copper wire, said Feargal Brennan, reader in mechanical engineering at the university. ‘We are providing laboratory quality information in the field, with a device that people do not need PhDs in stress analysis to use.’

Existing systems are also expensive and cumbersome, while the wireless device will cost less than £100 when it is ready for commercialisation. The prototype is the size of a PDA, but the team would have no difficulty in reducing it to half that size, he said.

The device has sufficient battery and memory power for it to stay in the field for the lifetime of the structure it is monitoring. ‘It recognises and measures any structurally significant event, and remembers it so that when you go along as part of your normal maintenance check or after any event, you can interrogate it.’

The self-calibrating device could be used as a stress memory tool for the railways, where it would allow track inspections to be targeted on areas that really need them, said Brennan. ‘It can point to where you should be looking for rail cracks, and where you should not bother wasting your resources. Invariably you are going to have a lower chance of success if you spend 90 per cent of your time looking in the wrong place.’

The company is already running field trials of the system with a major rail operator, and has also been talking to transport fleets about using it to monitor the stress placed on truck suspensions. With huge variations in road conditions throughout the world, installing two or three sensors along a vehicle’s suspension system would alert fleet managers to when any maintenance work is needed.

‘We are not interested in dictating to people where they should take their measurements,’ said Brennan. ‘they would identify the critical points themselves. all we would provide is a miniature sensor that allows them to measure stress wherever they want.’

The MoD is also interested in the device for collecting information on the frequency that artillery equipment is fired in battle, and for planning logistical support. By placing the recording devices on bridges, logistics teams can learn whether tanks, trucks or troops are moving towards them.