Finite-strain formulation and FE implementation of a constitutive model for powder compaction

Abstract

A finite-strain formulation is developed, implemented and tested for a constitutive model capable of describing the transition from granular to fully dense state during cold forming of ceramic powder. This constitutive model (as well as many others employed for geomaterials) embodies a number of features, such as pressuresensitive yielding, complex hardening rules and elastoplastic coupling, posing considerable problems in a finite-strain formulation and numerical implementation. A number of strategies are proposed to overcome the related problems, in particular, a neo-Hookean type of modification to the elastic potential and the adoption of the second Piola-Kirchhoff stress referred to the intermediate configuration to describe yielding. An incremental scheme compatible with the formulation for elastoplastic coupling at finite strain is also developed, and the corresponding constitutive update problem is solved by applying a return mapping algorithm.

Thermo-mechanical modelling of rock-like materials at very high temperature: Application to ceramic refractories

“…This could be done along the lines of existing approaches, as those proposed in (e.g.) [28], [30], [18], [19], [4], [5], and [6].…”

“…However, since both N cc and N cf depend on temperature and on plastic strains through eqns. (28) and 29, the functional dependency of ψ can equivalently, but more consistently, be expressed as…”

“…In any case, due to the above assumptions, a thermal loading-unloading cycle performed at negligible applied stress aects the nal properties of the material, due to the irreversible changes of N cc and N cf induced by temperature variations through eqns. (28) and (29). The free energy density function is assumed to take the form…”

“…The number of closed and cured cracks, N cc and N cf , is evaluated by using eqns. (28) and (29). When the material is completely uncemented, N cf = 0, then the tensile strength is null P t = 0, and P c becomes equal to the preconsolidation pressure of a loose (uncemented) geomaterial plus a contribution due to closed microcracks, namely…”

Computational modelling and experimental validation of industrial forming processes by cold pressing of aluminum silicate powder

“…The constitutive model was originally developed for the description of the compaction of alumina powder by Bigoni and co-workers [12][13][14][15][16]. That model has been modified in the present work, so as to make it more suitable for the description of the compaction of aluminum silicate powder.…”