A Non-Contact Varying Temperature Strain Measuring System Based on Digital Image Correlation

Abstract

An effective varying temperature digital image correlation (DIC) measurement is established for non-contact full-field deformation and strain measurement at varying temperatures. The test planar specimen can be heated from room temperature to 200 °C accurately using the temperature-controlled chamber. The digital images of the test specimen surface at various temperatures are recorded using an ordinary optical imaging system. In order to avoid the influence of variations in refractive index of the air at different temperatures, image averaging method was used to obtain high quality images of the specimen surface. The gradient-based DIC technique is used to extract full-field inplane thermal deformation from the corrected images. For verification, the thermal deformation fields and the values of coefficient of thermal expansion (CTEs) of 45 steel specimen are measured and compared with the literature values, confirming the effectiveness and accuracy of the proposed technique and method. The experimental results reveal that the proposed technique with image averaging method is able to accurately extract full-field thermal deformation at the temperature range of room temperature up to 200 °C.