Investigating tool engagement in groundwood pulping: finite element modelling and in-situ observations at the microscale

Abstract

With industrial groundwood pulping processes relying on carefully designed grit surfaces being developed for commercial use, it is increasingly important to understand the mechanisms occurring in the contact between wood and tool. We present a methodology to experimentally and numerically analyse the effect of different tool geometries on the groundwood pulping defibration process. Using a combination of high-resolution experimental and numerical methods, including finite element (FE) models, digital volume correlation (DVC) of synchrotron radiation-based X-ray computed tomography (CT) of initial grinding and lab-scale grinding experiments, this paper aims to study such mechanisms. Three different asperity geometries were studied in FE simulations and in grinding of wood from Norway spruce. We found a good correlation between strains obtained from FE models and strains calculated using DVC from stacks of CT images of initial grinding. We also correlate the strains obtained from numerical models to the integrity of the separated fibres in lab-scale grinding experiments. In conclusion, we found that, by modifying the asperity geometries, it is, to some extent, possible to control the underlying mechanisms, enabling development of better tools in terms of efficiency, quality of the fibres and stability of the groundwood pulping process.

Digital Volume Correlation analyses to study deformation and damage mechanisms of teak in torsion

“…Global DVC was utilized to assess swelling of spruce wood from dry to wet humidity states with 27 µm elements [26]. Indentation tests on Norway spruce were also studied with such approach with elements of the order of 130 µm in length [27]. To the best of the authors' knowledge, no in situ torsion test has so far been reported for wood.…”

In-situ quantification of microscopic contributions of individual cells to macroscopic wood deformation with synchrotron computed tomography

“…Best wood species can then be chosen according to mechanical stability for a certain application. Wood-based composite production processes can be optimized 18 , 19 . New, more damage resistant wood-based products with better performance and improved durability can be designed 20 .…”