Calibration of the thermoelastic stress analysis technique under sinusoidal and random loading conditions

For the past five years the National Engineering Laboratory (NEL) has been engaged in a research programme investigating the applications of thermoelastic stress analysis to engineering structures. This paper discusses the use of a uniformly stressed component for the calibration of SPATE (Stress Pattern Analysis by Thermal Emission). Experimental results for sinusoidal loading on a carbon steel are compared with a theoretical prediction based upon material properties and instrument characteristics. A calibration technique which is suitable for the measurement of quantitative stresses under random loading, including modal behaviour, is also described.