Modelling the compression, shear and volume behaviour of final bagasse

Computer modelling of milling in combination with experimental measurements offers the promise of increased throughput, increased sugar extraction, and decreased bagasse moisture content. Central to computer modelling is a description of the deformation behaviour of the bagasse. Last year's ASSCT conference paper by the above authors showed that, for the range of compactions tested, prepared cane, first bagasse and final bagasse behave in the same manner as a soil (sand, clay) in both compression and shear. Consequently, the methodology used for the development of soils materials models is expected to be of value in the development of a bagasse material model. This paper seeks to determine physically meaningful final bagasse material parameters from measured behaviour in a direct shear test. The paper identifies the loading conditions from which the material parameters can be obtained, and their magnitudes. Finally, the relevance of loading situations in a direct shear test are compared to loading situations in a milling unit: the initial compression of the material as it moves towards the underfeed nip, the subsequent unloading and reloading as the material exits the underfeed nip and moves towards the pressure feeder nip (and subsequent unloading and then reloading to much higher pressures between the mill rolls), and the shear behaviour which is believed to have a strong bearing on the feeding performance of a mill. The ability of material models currently used in mill modelling to reproduce the above behaviour is assessed and their limitations are identified. A platform is established to identify an adequate material model.