Research on the structure stress analysis based on IR lock in thermography

This paper describes a theoretical and experimental analysis on full-filed stress distribution from thermoelastic measurements and its application to determination of stress concentration. The sum of the principle stress can be measured by TSA. The IR Lock in Thermography has been applied to measure the structure stress distribution by its high thermal resolving. In this study, the thermoelastic effect model is developed to study the relationship between the temperature and the applied stress in an elastic material. The FEM is used to study the thermodynamic effect with classical thermoelastic equation, and the valid condition is obtained that the adiabatic loading conditions prevail. The applied loading frequency directly effect on the adiabatic loading conditions for given elastic material. The experiment was carried out with carbon steel structure with a hole for various loading frequency by Lock in thermography. The experimental results show the stress distribution can be measure and a factor is obtained to measure stress in the non-adiabatic conditions (Low loading frequency). It was found that the structure stress can be evaluated with good accuracies by the lock in thermography.