The Added Value of Infrared Thermography in the Measurement of Temperature-stress Coupled Effects

Abstract

The attention of the present paper is focused on the use of infrared thermography to measure the very small temperature variations which are linked to thermo- elastic effects. Hereafter, the latter are associated with material volume variations undergone by a cantilever beam under cyclic bending load. This is a difficult task since the temperature variations can be very small and at the edge of the instrument resolution. The task creates the problem of the infrared camera choice since the sensor should have high thermal sensitivity and low noise, which may be almost impossible to achieve. In fact, a quantum well infrared photodetector (QWIP) is well suited for sensing the small thermal radiation associated with thermo-elastic phenomena, but it is affected by noise, mainly dark current effects, which can be of the same order of magnitude of the quantity to be measured. However, with the aid of a reference sample (reference-area method) it is possible to eliminate most of the instrumental and environmental noise so as to obtain reliable measurements. This method allows extending the use of an infrared imaging device outside its stated resolution range and has been proposed and described in previous work. The intention now is to better validate the reference-area method as applied to a QWIP detector, an indium antimonide (InSb) detector and a microbolometer one, also with the aid of a black body. Indeed, the method represents a simple noise correction approach to be used with any detector and which may open the door to a wider exploitation of remote infrared imaging devices.

Keywords

• Infrared thermography
• Cyclic bending tests
• Thermo-elastic effect
• Temperature variations
• Radiation sensing
• Signal treatment
• Correction of infrared detector noise.