Effects of Sample Shapes and Thickness on Distribution of Temperature inside the Mineral Ilmenite Due to Microwave Heating

Abstract

The study of interaction between microwave radiation and minerals is gaining increasing interest in the field of minerals and material processing. Further studies are, however, still required to deepen the understanding of such microwave heating mechanisms in order to develop innovative techniques for mineral treatment using microwave heating. In this paper, effects of sample shapes and thickness on the distribution of temperature inside the mineral ilmenite (FeTiO3) due to microwave heating were numerically studied using the finite element (FE) method. The analysis was carried out in such a way that the flux of microwave energy was converted into an equivalent amount of heat generation in the mineral through the Poynting theorem of conservation of energy for the electromagnetic field. In this study, as a first attempt, the cylinder and slab of ilmenite were modeled to be irradiated from top and bottom surfaces with the variation of cylinder and slab thicknesses. Temperature-dependent material properties of ilmenite were taken into account in the FE simulation. Corresponding boundary conditions were then applied accordingly to the cylinder and slab of ilmenite with comparable characteristic length. Numerical results showed that, in terms of temperature differences between locations having maximum and minimum temperatures, slab geometries tended to produce higher values in comparison to those of cylinder geometries with the thickness variation, while the profiles of temperature inside the ilmenite samples were similar for both geometries. For the same duration of microwave heating, the slab geometry, hence, induced greater non-uniformity of temperature inside the ilmenite. It was also observed that, for the ilmenite samples with thickness value greater than 1.5 cm, the hotspot locations were not in the center of the sample, but on the surface of sample. Moreover, from several thickness values considered in this study, the ilmenite sample with thickness value of 3 cm gave a good trade-off between the maximum temperature value attained and temperature differences inside the sample, for both geometries. Thus, the shape and thickness of ilmenite samples affect the effectiveness of microwave heating of ilmenite, in terms of maximum temperature attained, temperature differences, and uniformity of temperature.

Informative Bounds of Neural Networks Prediction for Composite Fatigue Life Under Variable Amplitude Loading

“…As can be seen from Figs 6 and 7, the informative bounds of NN prediction represented as the lower and upper bounds of prediction were provided and the noticeable discrepancies were well confined within the conservative bounds of prediction from the highest estimated standard deviation value. Combined forward (Hidayat et al, 2016;Hidayat et al, 2020) and inverse techniques in fatigue life assessment of materials may be further explored to obtain deeper analysis on the aspect of prediction bounds.…”

Efficient Fatigue Life Assessment of Composite Materials by Using a Hybrid Surrogate Modeling

“…Further efforts are still required to get more comprehensive understanding on the relationship which might exist between failure mechanisms taking place in the composite materials at both micro and macro scales and the way of such mechanisms may be manifested in the corresponding fatigue data (such as the fatigue scatter), which might be possible to be captured further by some NN models. In addition, another interesting extension of study is that how to handle multivariable amplitude loadings, including multiaxial fatigue loadings, in a more integrated way in the fatigue life assessment using NN, other surrogate as well as combined forward (Hidayat et al, 2016;Hidayat et al, 2017;Hidayat et al, 2020) and inverse modelling techniques. These may be interesting as subjects of further study.…”

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