SUMMARYAn Eulerean large-strain finite element formulation is presented to simulate static soil penetration. The method is an extension of the Updated Lagrangean description to an Eulerean formulation taking into account convection of deformation-history-dependent properties as well as material properties. The strength of the soil is characterized by a non-associated Drucker-Prager criterion which depends on peak and critical friction angles. The model is applied to cone penetration in two-layer systems: (a) clay on sand and (b) sand on clay.

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Abstract. Constitutive equations for simulations of thermo-mechanical processes, involving solid-solid phase transformations are derived. The rate of phase transformation is assumed to depend on temperature as well as stress state. The constitutive equations comprise latent heat of transformation, transformation dilatation and transformation induced plasticity. Consistent moduli are derived for finite time steps. The constitutive equations are implemented in a finite element model, which has displacements and heat flows as primary variables. The temperatures, phase fractions, stresses and equivalent strains are treated as state variables and are evaluated in element integration points. The model is demonstrated on simulations of laser hardening.

A new material description for sheet metal forming has been developed. The material description exists of the Vegter yield criterion and a physically based hardening rule. In contrast to most former criteria, the Vegter yield criterion is based on measurements of multi-axial yield stress states. The yield criterion is extended with a physically based hardening rule, in which the flow stress depends on the strain and strain rate. To measure the multi-axial stress states a biaxial test equipment is being designed. The test equipment will be capable of imposing a shear deformation and a plane strain deformation, including combinations of both deformations. To check whether the bi-axial test equipment will give reliable results, a Finite Element model of a part of the test piece and the clamp equipment is constructed.

A new integration algorithm is described for large strain plastic deformations. The algorithm degenerates to the Euler forward elastoplastic-plastic model for small strain increments and to the rigid-plastic model for large strain increments. The model benefits from the advantages of both models: accuracy and fast convergence over a large range of strain increments.