Applicability of image correlation techniques to characterise asymmetric refractory creep during bending tests

Abstract

The design of fibre reinforced refractory castable structures for high temperature applications requires the characterisation of the material creep behaviour. As many other heterogeneous ceramics, these materials creep faster under tensile stresses than under compressive ones because of the motion of hard particles in a soft matrix. Bending tests have been performed to characterise the creep behaviour of the considered material, and 3D digital image correlation is used to obtain strain fields after interrupted tests. The position of the neutral axis, defined here from the residual inelastic strain field, allows to highlight the asymmetry of creep and to evaluate the asymmetry ratio.

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

“…In this work, this datum is obtained using a kinematic full-field measurement performed at room temperature after the interruption of the bending creep test at 1200°C [19]. This method is much easier to apply than monitoring the test at high temperature.…”

Analysis of Asymmetrical Creep of a Ceramic at 1350°C by Digital Image Correlation

“…), or not. Several remarks are drawn: As DIC is started after the initial load has been applied, the measured strain field corresponds to the current total strain minus the initial elastic strain The strain values obtained by Q4‐DIC and Beam‐DIC are equal within ± 0.01% margin.…”

“…In Beam-DIC (right), the horizontal field varies linearly with the vertical coordinate as it is directly computed from analytical functions [Eq. (6)]. The minimum and maximum final strains are directly available, namely, e comp = À0.619% and e tens = +0.877% after 45 h. It corresponds to a ratio of about 1.42 between the tensile and compressive strains.…”

“…Most of the time, the tensile and compressive behaviors are assumed to be symmetric so that the vertical deflection measurement is sufficient to calculate the flexural creep strain assuming perfect boundary conditions. But many ceramics, especially at high temperatures, may have an asymmetric creep behavior . For such ceramics, uniaxial tensile tests may be performed, yet they are very delicate .…”

“…But many ceramics, especially at high temperatures, may have an asymmetric creep behavior. [5][6][7] For such ceramics, uniaxial tensile tests may be performed, yet they are very delicate. 8 Compression and flexural tests have been consid-ered, 9 even though the identification of the tensile behavior is not straightforward.…”