In the present work, the squeeze flow geometry is used to investigate the properties of concentrated suspensions. The suspensions consist on hard glass spherical particles dispersed in a viscoplastic fluid. With such a material, following the solid volume fraction, the material rheological behaviour ranges from purely viscoplastic fluid to granular media. During the squeezing action, the materi...

A viscoplastic deformation model considering material damage is used to predict hot tear formation in a permanent mold magnesium alloy casting. The simulation model calculates the solid deformation and ductile damage. The viscoplastic constitutive theory accounts for temperature dependent properties and includes creep and isotropic hardening. Ductile damage theory is used to find mechanically i...

In order to investigate the impact of microstructures and deformation mechanisms on the ductility of materials, the criterion first proposed by Rice is applied to elastic-plastic tangent moduli derived from a large strain micromechanical model combined with a self-consistent scale transition technique. This approach takes into account several microstructural aspects for polycrystalline aggregat...

We studied the elastic moduli, ductile creep behavior, and brittle strength of shale-gas reservoir rocks from Barnett, Haynesville, Eagle Ford, and Fort St. John shale in a series of triaxial laboratory experiments. We found a strong correlation between the shale compositions, in particular, the volume of clay plus kerogen and intact rock strength, frictional strength, and viscoplastic creep. V...

The viscoplastic behavior of a carbon-fiber/polymer matrix composite was investigated through two different modeling efforts. The first model is phenomenological in nature and utilizes the tensile and stress relaxation experiments to predict the creep strain. The phenomenological model was constructed based on the overstress viscoplastic model. In the second model, the composite viscoplastic be...

Recent studies of excessive multidecade deflections of prestressed segmentally erected box girders revealed that more accurate predictions of the prestress loss due to steel relaxation are needed for the design of large-span creep-sensitive structures. In particular, the loss needs to be calculated as part of creep structural analysis, during which the strain of concrete to which the prestressi...

ABSTRACT. This work is focused on the numerical implementation of thermo-viscoplastic constitutive equations in small and finite strain contexts using FEM. A length scale parameter is introduced implicitly through viscosity in order to address strain localization in the (initial) boundary value problems. The mathematical structure of the infinitesimal viscoplasticity theory is concise and simil...

Cam-Clay nonassociative plasticity exhibits both hardening and softening behaviour, depending on the loading. For many initial data the classical formulation of the quasistatic evolution problem has no smooth solution. We propose here a notion of generalized solution, based on a viscoplastic approximation. To study the limit of the viscoplastic evolutions we rescale time, in such a way that the...

This paper deals with unified elastoplastic and elastic-viscoplastic constitutive equations for metals submitted to large deformations. We present here a newly developed time integration algorithm which is an extension to the viscoplastic range of the classical radial return algorithm for plasticity. The resulting implicit algorithm is both efficient and very inexpensive. This algorithm is also...