Eliminating environmental effects from Lamb wave-basedstructural health monitoring

摘要

Structural Health Monitoring using Lamb waves is based on the theory of elastic waves propagating inrnplates. Signal attenuation and mode conversion are used for damage detection. It is well known that thernvoltage amplitude from low-profile piezoceramic sensors used for inspection may change not only due torndamage but also due to inappropriate transducer coupling and temperature effects. This paper studies therneffect of temperature on Lamb wave responses and attempts to alleviate the problem. The work involvesrna simple experiment in which two piezoelectric ceramics are bonded on an aluminium plate. The plate isrnexposed to various levels of temperature. A visualisation technique and a novelty detection technique arernused to show the effect of the temperature changes. The plate was then subjected to damage and the series ofrntests and analysis repeated in order to give some comparison between the effects of damage and temperaturernchange upon the responses. Several methods are investigated to try to eliminate the effects of the temperaturernvariation whilst retaining the sensitivity to the damage.