Computational and experimental modelling of the crushing of prepared sugar cane

This thesis presents the investigation and application of porous media mechanics and elasto-plastic constitutive theory for the crushing of prepared sugar cane using finite element simulation. This research specifically investigates the experiments carried out on C. R. Murry Advanced Experimental Milling Facility using cane that has also passed through a series of basic tests to characterise its properties for the computational models. For isotropic plastic material behaviour, constitutive models that represent yielding under hydrostatic pressures are applied. The constitutive behaviour of the solid skeleton, and the plastic strain hardening response are derived from a series of slow speed confined uniaxial compression experiments. The liquid flow within fibrous solid matrix of prepared cane is modelled by applying Darcy's law, and the coefficient of permeability therefore was determined experimentally. The finite element technique applied to the crushing process, couple the elastoplastic constitutive theory for the solid fibre and the Darcy's liquid flow theory for the liquid juice in conjunction with the frictional relation between the roller and blanket material. The material law has been coded initially into a two-dimensional plane strain computer model. Series of experiments on two-roll mill was conducted. The two-dimensional plane strain model predicted the roll load in agreement with experimental values, however failed to capture the tangential component of compression and the torque values were 50% lower than the experimental values. However, numerical prediction of a flat roll surface matched well in roll load and torque with experimental values as the stress levels associated with grooves are absent. The rolls were then modelled with grooves in threedimension. The three-dimensional model captured high and low compression regions in groove tip and base respectively. The roll loads as well as roll torques matched well with experimental values