The Axisymmetric Extrusion of Solid Chocolate and the Effect of Die Geometry

摘要

This paper investigates some of the effects of axisymmetric die geometry and flowrate during the isothermal extrusion of solid chocolate. Experimental observations, such as the material exhibiting a yield stress, flowrate independence and irreversible deformation, indicate that solid chocolate can be modelled using a rigid perfect plastic constitutive model (usually applied to the characterisation of metal forming processes). Numerically obtained extrusion pressures for a range of area reductions, using a commercial finite element package (ABAQUS) in combination with a remeshing code, are compared to experimental data to determine the uniaxial yield stress of the material. Analytical approximations are used to verify the numerical results. A study of the material behaviour in the die land, however, shows that the perfect plastic description can be inadequate in predicting extrusion pressures under certain conditions.