A BETTER MATERIAL PARAMETER FOR DESCRIBING THE STRAIN HARDENING BEHAVIOUR OF BAGASSE

The prediction of roll load and mill torque in sugarcane roller mills requires knowledge of the relationship between the deformation occurring in bagasse as it passes through the mill and the pressure caused by that deformation. Such a relationship was used in the empirical models developed at the University of Queensland in the 1950s and, in an alternative form, is currently used in the computational models adopted by milling researchers. The relationships between deformation and pressure used previously were developed through linear regression analysis of load and displacement data from compression tests, and the regression constants have little physical significance. This approach is in contrast to the approach commonly used with the soils model used in current computational models. The deformation and pressure relationship in the soils model is typically defined by a material parameter called £f that has some physical significance. Sugar Research Institute researchers have calculated £f for bagasse and have found that its value changes with the pressure range being studied. This paper introduces an alternative material parameter, named £f1 to preserve its intent, which is considered appropriate to define the deformation and pressure relationship across the entire pressure range relevant to milling. Theory is also presented to convert the deformation and pressure relationship into a hardening law for direct use in the computational model.