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

Abstract

The glass industry requires the use of innovative ceramics that enable for long lifetimes. At very high temperatures, one of the key parameters for ceramics is their creep resistance. The characterization of the creep behavior, usually assessed through flexural tests, can be complex when an asymmetry appears between tension and compression. To detect and quantify such asymmetrical behaviors, the use of Digital Image Correlation (DIC) is proposed. First, several challenges are to be tackled for DIC at high temperature, namely, the random pattern stability, the radiation filtering and the heat haze. They are exacerbated by the limited possibilities to heat ceramics, the nonuniform strain fields and their low levels. Beyond several experimental developments, the strain uncertainties are decreased thanks to the use of two global approaches of DIC based on ad hoc finite‐element kinematics. Last, the proposed methodology is applied to the analysis of asymmetric creep at 1350°C of an industrial zircon ceramic designed for its high creep resistance.

Spatiotemporal regularization for digital image correlation: Application to infrared camera frames

“…This approach somehow extends the strategy used for fighting the adverse effect of turbulent thermal plumes in high-temperature mechanical tests that consisted in averaging images with a long exposure time. 40 In the latter case, the time average of convective displacements is expected to be null, whereas in the present study, it is expected to be orthogonal to the model-based dominant temporal evolution. The effects of convection on images are still present but not captured by the constrained kinematics.…”

“…It is important for the success of this strategy that the temporal mode of the convection part of the displacement field has a small projection (ideally null) with respect to those of the physical displacement. This approach somehow extends the strategy used for fighting the adverse effect of turbulent thermal plumes in high‐temperature mechanical tests that consisted in averaging images with a long exposure time . In the latter case, the time average of convective displacements is expected to be null, whereas in the present study, it is expected to be orthogonal to the model‐based dominant temporal evolution.…”

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

“…It is also possible to calculate that the neutral axis has shifted by + 1.3 mm towards the top of the sample. This work has proven the feasibility of using DIC at high temperature to have access to unique information during conventional tests -bending tests in our case [14]. When this method has been applied to asymmetrical creep, it has been possible to reveal a difference in creep rates of 1.5 between tension and compression.…”

“…Modelling the in-use behaviour of refractory structures requires a suitable model that is able to describe the asymmetric creep as evidenced by the experiment [11,14,17]. In the case of refractory concrete, the variability inherent to the material necessitates to identify the parameters of the models for many samples and several processing and testing conditions.…”

“…However, this is often very complex at high temperature on ceramics [12]. A second possibility consists of running classical bending tests that are monitored via Digital Image Correlation to measure tensile and compressive creep rates in the same time [13] using reverse identification to obtain the uniaxial creep parameters [14]. This method requires dedicated experimental and numerical developments that will be presented hereafter.…”