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In this paper the problem of a plane strain hydraulic fracture propagating in an elasto-plastic material is analyzed. A new stress redistribution model for the proximity of the fracture tip is formulated and a resulting plasticity-dependent crack propagation condition is introduced. A modified variant of the KGD problem that accounts for the plastic deformations in the near-tip zone only is proposed. It is demonstrated that this model can be a credible substitute for the full elasto-plastic hydraulic fracture problem in the case of moderate plastic deformation. The crack-tip shielding effect introduced by the plastic deformation is quantified. [ABSTRACT FROM AUTHOR]

We present results of a parametric study on shearband formation in geomaterials, examining the influence of material dilatancy on shearband properties. The study is based on a new higher order continuum theory, called gradient elastoplasticity, developed to model localization of deformation. We present results for two problems with different initial stress fields: The biaxial test and the hollow cylinder test. We show that nonassociativity promotes bifurcation at lower deformation, leading to localized deformation and more abrupt final failure. Both the inclination and thickness of the calculated shearbands decrease with increasing nonassociativity. Gradient elastoplasticity is capable of reproducing the experimentally observed localized failure modes, including details such as reorientation of shearband close to a free boundary. [ABSTRACT FROM AUTHOR]

Presents information on a study which focused on a linear bifurcation analysis for pressure sensitive elastoplastic hollow cylinders under radial surface loads. Derivation of perturbed equilibrium equations; Eigenmodes solution and constitutive specification; Numerical examples; Conclusions.

Abstract: This paper presents a decoupled Arbitrary Lagrangian–Eulerian (ALE) approach for the large deformation analysis of plane-strain elastoplastic problems. In this decoupled approach, the Eulerian step consists of first remeshing the deformed continuum and then remapping the state variables at the new quadrature points. Remeshing is performed without altering the element topology of the original mesh with the aid of the Spring Analogy Method enhanced with torsional springs. Before remeshing, nodes at free boundaries are relocated using an analytical approach, in order to preserve a good node distribution throughout the analysis. State variable remapping is achieved through the Radial Basis Point Interpolation Functions scheme. Large deformation elastoplastic analyses of two plane strain example problems are conducted using the presented ALE approach to test its robustness and effectiveness. The continuum is modeled as a Tresca or Mohr–Coulomb elastic–perfectly plastic material, while the meshes consist of second-order finite elements. The numerical results demonstrate that the present methodology is capable of predicting with adequate accuracy the load–displacement response even in analyses involving very large translations of the loaded boundary. [Copyright &y& Elsevier]