Towards a hybrid infrared approach for damage assessment

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Description/Abstract

The thermoelastic response obtained from an infra-red (IR) detector contains two
components: the magnitude of the small stress induced temperature change caused by the
thermoelastic effect and the phase angle of the temperature change relative to a reference signal
generated by an application of a stress change. The phase angle is related to nonlinearity in the
thermoelastic response and departures from the simple linear relationship that underpins
thermoelastic stress analysis (TSA). The phase data could be used to make an assessment of
temperature evolutions caused by viscoelastic behaviour resulting from damage and provide a basis
for its evaluation. In the current paper the physics of other infra-red techniques used for nondestructive
evaluation is used to better understand the nature of the thermoelastic response. The
objective is to provide better exploitation of TSA by alternative processing of the IR measurements.
Three case studies are presented that demonstrate the potential of the alternative processing for
evaluating damage.