Influence of cyclic moisture loading and unloading on the mechanical properties of alumina oxide granules

Abstract

The influence of cyclic moisture loading and unloading on the material behavior and the mechanical properties of γ -Al 2 O 3 granules has been extensively studied by uniaxial compression tests. For this purpose, the granules have been treated with two different types of moisture loading and unloading cycles. The first cycle type consists of the moistening of granules in a climate chamber using wet air and complete immersion in a water bath followed by drying in a drying chamber. The second cycle type consists only of the moistening of granules in a climate chamber followed by drying in a drying chamber. During treatment with wet air, the mechanical properties of granules decrease with increasing moisture content. The force-displacement curves flatten and the fracture force, the fracture strength as well as the specific fracture energy significantly decreases. Additional treatment by immersion in a water bath has a further, but, less intense influence on the mechanical properties. On subsequent drying of granules in a drying chamber in order to achieve regeneration, the initial condition can only be partially restored. With increasing number of moisture loading and unloading cycles, a continuous decrease in the strength of granules takes place due to non-regenerative damage of the structure. Furthermore, a significant relationship between granule size and damage could be observed. B Peter Müller

Comparison of measurement systems for free fall tests and calculations of the coefficient of restitution

“…The used hygroscopic zeolite 4A and γ-alumina granules consist of agglomerated primary granules and are held together by solid bridge bonds [30,31]. Table 2 summarizes several material properties of the granules and table 3 shows relevant properties of the impact plate.…”