Application of digital image analysis to strain measurement at elevated temperature

Abstract

Digital imaging techniques are applied to the measurement of surface displacement and strain at elevated temperatures. A simple surface preparation using high temperature paint together with a CCD video camera for digital imaging serve as the basis for the measurements. Mathemetical correlation of the surface intensity pattern between reference and deformed states is used to measure local surface deformation. The method is non‐contacting and full field. Displacement and strain measurements have been made at temperatures to 600°. Coefficients of thermal expansion of three metals have been measured using this technique and compared to strain gauge and handbook values. Limitations and potential extensions of the method are discussed.