Study of the causes of uncertainty in thermoelasticity measurements of mechanical components

Thermoelastic stress analysis (TSA) is a contactless technique for measuring stress distributions in mechanical components stressed by dynamic loads. The application of TSA was proposed since more than twenty years ago. In many papers available in literature thermoelasticity systems are used not to perform quantitative measure but only for non-destructive evaluation of structural integrity of components, joints etc. In the present paper a systematic experimental work is carried out in order to better understand what is possible to measure on simple specimen of mechanical components. This work describes the characteristics, analyses the main causes of uncertainty and illustrates a series of operative methods for reducing its effects. More specifically, the effects of the angle of view between the thermographic camera and the surface of the object are studied, along with those due to the heat transmission by conduction between the various parts of the thing being measured according to the stress frequencies. The analyses, both theoretical and experimental, are aimed at defining the operational limits and optimal measurement and test conditions in relation to the measurement uncertainty that is considered tolerable in the specific application.