Mechanical properties of agglomerates

The mechanical properties of dry and wet agglomerates are reviewed in the c ontext of continuum solid and fluid mechanics and fracture mechanics. The f ocus is on practical measurements of tensile strength, yield strength, hard ness and fracture toughness, and how they define the attrition behavior of agglomerates. Well-established mechanical testing methods can be applied to agglomerates, but certain limitations apply due to the nature of agglomera tes being inherently non-equilibrium (glassy), anisotropic, and compressibl e. The mechanical response of agglomerates may vary from brittle, elastic-p lastic (for most dry agglomerates) to elastoviscoplastic and fully plastic (for wet agglomerates) depending on preparation method, environment, struct ure and loading conditions. This transition from solid to liquid-like behav ior can be followed by applying solid/fracture mechanics and theology-based testing, respectively. It is clear that most available practical measures of agglomerate mechanical behavior are not intrinsic, i.e. independent of t est specimen geometry and the manner in which stress is applied. Therefore, selection and execution of measurements must be guided by loading conditio ns and agglomerate size and structure from the process of concern. Micromec hanical modeling addresses some of the dependence of mechanical properties on the structure of agglomerates [e.g., porosity] and the properties of the ir primary constituents, but it cannot describe quantitatively bulk deforma tion and fracture of agglomerates. For this reason, agglomerate formulation s are still tailored to achieve desired performance by empirical correlatio n of primary particle and agglomerate structure to mechanical properties. ( C) 2001 Elsevier Science B.V. All rights reserved.