<title>New Developments In The Use Of Thermal Measurement Techniques For Structural Design Engineering</title>

Abstract

This paper describes a novel method of stress determination in structures under dynamic loading conditions. The principle is based on the thermodynamic property of a material in which, under adiabatic conditions, heat is produced or absorbed in direct proportion to the magnitude of the stresses to which it is being subjected. An instrument is described which uses infra -red radiation to measure, remotely, the resulting minute local temperature changes in the material, with oscillating mirrors to provide a raster type scan of the item under test. Spatial resolution down to 1 mm and a temperature discrimination of about 0.002 °C have been achieved, this latter representing a stress change of less than 300 lb /in2 in steel.