Non-contact measurement of linear thermal expansion coefficients of solid materials by infrared image correlation

Abstract

A new non-contact optical method (IIC, infrared image correlation) for the determination of the coefficients of thermal expansion of solid materials is presented. The proposed method is based on performing a digital image correlation between thermal images recorded at different temperatures by means of an infrared camera. It allows the coefficient of thermal expansion of both isotropic and anisotropic solid materials to be determined by measuring simultaneously the fractional increase in length and the actual thermal field over a small region of interest in which a dual-emissivity stochastic speckle pattern has been created. The results reported in this paper prove the effectiveness of the proposed method that can be applied either to carry out reference measurements in laboratory or to evaluate thermal stresses and strains on structural components in-field.

Contactless Characterization of Metals’ Thermal Expansion Coefficient by a Free-Space RF Measurement

“…Another solution to extract β is to develop (7) and (8) using Taylor series of first order and to note that the frequency shift ∆f caused by a variation of the temperature is equal in first approximation to…”

“…convert pixel to length [7]. For some materials such as crystals, Xray diffraction can be used to measure the crystal lattice parameter as a function of the temperature in order to extract its thermal expansion [8].…”

New advances in the laboratory characterization of refractories: testing and modelling

“…Classic dilatometers are routinely used and, due to their high accuracy, allow the coefficient of thermal expansion, shrinkage induced by sintering, glassing transition, and chemical changes to be determined. Contactless optical instruments have pushed the temperature limit back and therefore can be used to melt samples during the measurement [20,21]. However, the sample size limitation of a few millimetres makes tests difficult on very heterogeneous materials that are made of aggregates of a few millimetres and, therefore, require large representative volumes.…”

Simultaneous assessment of Lagrangian strain and temperature fields by improved IR-DIC strategy

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