Alternative calibration techniques for quantitative thermoelastic stress analysis

In recent years thermoelastic stress analysis has been established as an important experimental technique. The SPATE (Stress Pattern Analysis by Thermal Emissions) system, marketed by Ometron Ltd., is the standard equipment for thermoelastic stress analysis. The signal obtained from the SPATE equipment is directly proportional to the sum of the principal stress on the surface of the structure under evaluation. For quantitative stress analysis accurate calibration constants must be obtained; these are dependent on the radiometric properties of the SPATE system detector and the material properties and condition of the surface in question. This paper describes a number of calibration techniques commonly in use. The factors which affect the accuracy of each technique are discussed in detail. An experimental calibration study of a “steel” is also included.