CrackFirst ^TM sensor from TWI warns of fatigue failures

TWI has managed the development of a device that measures the amount of fatigue suffered by a welded structure. At the heart of the CrackFirst ^TM system is a sensor which, when installed on the structure, indicates the portion of the design life that's been consumed and enables engineers to estimate its remaining life.

Unlike a typical strain gauge, which monitors the amount of strain at the point where it is attached to the structure, CrackFirst ^TM senses the actual amount of fatigue damage that a structure has suffered. It can be used on any welded steel construction which sees cyclic loading, such as bridges, vehicle chasses, cranes and offshore structures.

The device comprises a steel shim that cracks at a rate that can be related to the fatigue damage being suffered by the structure. Thin film circuitry on the shim is used to measure the crack length, and associated electronics are used to record the sensor's performance over specified time periods.

Designed to give advanced notice of potentially catastrophic fatigue failures, the sensor will help owners avoid the high costs, and health and safety implications, of such failures. It does this by monitoring the percentage of the design fatigue life which has been used up. The warning period is variable, but it can be expected to give months or years of warning of a structure's end of life. The CrackFirst ^TM system will form an important part of many structural Health & Usage Monitoring Systems (HUMS).

The CrackFirst ^TM system was developed through the collaboration of TWI Ltd., FMB, Micro Circuit Engineering Ltd., UMIST and Caterpillar Peterlee (A division of Caterpillar (UK) Limited) in a project funded by the DTI's LINK Sensor and Sensor Systems for Industrial Applications Programme.

TWI acted as the project manager for the consortium and contributed to the design, manufacturing, laboratory testing and installation aspects of the project.

John Davenport, Programme Manager at TWI said: "TWI is very pleased to have been involved with this project. The CrackFirst? sensor system will save money for asset managers and reduce the incidence of structural failures. It's an innovative and robust solution to a real world problem."

TWI is currently involved in the final stages of development and in bringing the system to market. TWI welcomes enquiries from organisations interested in using the CrackFirst ^TM sensor system. Please contact Peter Tubby ( peter.tubby@twi.co.uk) or John Davenport ( john.davenport@twi.co.uk).

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