Loading-unloading contact law for micro-crystalline cellulose particles under large deformations

Abstract

A semi-empirical mechanistic contact law for micro-crystalline cellulose (Avicel PH-200) particles is proposed and characterized experimentally using force-displacement curves obtained from diametrical compression of single particles. The concepts of a shape factor and a master contact law are introduced first for elastic ellipsoidal particles, and subsequently generalized to plastic irregular particles. The proposed loading-unloading contact law is a function of three characteristic diameters (lengths of the principal axes of an approximated ellipsoid), a geometric parameter associated with the loading condition, three plastic and one elastic material properties. The force-displacement curves obtained using a micro-compression tester exhibit an apparent strain-hardening at distinctly different strain values, which is captured by the shape factor function and its geometric parameter. The three plastic material properties are log-normal distributions estimated from the loading experimental curves, while the elastic property is estimated from the unloading experimental curves. The study shows a very good agreement between predictions of the calibrated loading-unloading contact law and the experimental values.

Microfluidic In-Situ Measurement of Poisson’s Ratio of Hydrogels

“…Our characterization method is not limited to particles directly fabricated inside a microchannel but can also be used, for example, for protein or cell aggregates that can be flown into the microchannel. However, their potentially more complex shape and porosity can make the analysis less straightforward [31] and would require the use of effective strains and stresses to describe the particle deformation [32]. Moreover, if the condition σ zz = 0 is not verified, our method could be adapted to measure Poisson's ratio, which in that case derives from the formula ν/(1 − ν) = − xx /( yy + zz ).…”

Avian mud nest architecture by self-secreted saliva

“…The force, F , and displacement, δ, during the compression were recorded using a universal testing machine (Instron 3343). The tensile stress developed along the shortest principal axis is approximately σ = kF /(π R e ) 2 where R e = ab /(2 c ) and k is a constant that can vary between 2/π and 4/π depending on the geometry of the pellet ( 31 – 33 ). In our experiment, we kept k = 1 for simplicity.…”

A Review of Computational Models for the Flow of Milled Biomass Part I: Discrete-Particle Models

“…Second, particle–particle and particle–wall contact models to be developed and calibrated specifically for woody biomass such as loblolly pine are as important as good particle shape approximations but usually are not known a priori. The contact models for biomass materials and walls of specific types may be derived from physical tests in the form of semiempirical mechanistic contact laws . By using those laws in DEM simulations, it may allow even the conventional spherical DEM model to reproduce the bulk stress–strain behavior of certain biomass materials subjected to axial compression.…”