Abstract. Material nonlinearity is of great importance in many engineering problems. In this paper, we exploit NURBS-based isogeometric approach in solving materially nonlinear problems, i.e. elastoplastic problems. The von Mises model with linear isotropic hardening and kinematic hardening is presented, and furthermore the method can also be applied to other elastoplastic models without any loss of generality. The NURBS basis functions allow us to describe exactly the curved geometry of underlying problems and control efficiently the accuracy of approximation solution. Once the discretized system of non-linear equilibrium equation is obtained, the Newton-Raphson iterative scheme is used. Several numerical examples are tested. The accuracy and reliability of the proposed method are verified by comparing with results from ANSYS Workbench software.

In this paper, prediction of failed evolution of anisotropic voided ductile materials will be developed based on Dung’s microscopic damage model. An isotropic and anisotropic formulation of the Dung’s damage model that using von Mises yield criterion and Hill’s quadratic anisotropic yield criterion (1948) integrated with isotropic hardening rules of matrix material used to simulate the deep drawing process of aluminum alloy sheets. The model is implemented as a vectorized user-defined material subroutine (VUMAT) in the ABAQUS/Explicit commercial finite element code. The predictions of ductile crack behavior in the specimens based on void nucleation, growth and coelescence are compared with Gurson – Tvergaard – Needleman (GTN) model and experiment results from reference.

In this paper, the Dung’s microscopic damage model which depicts void growth under plastic deformation is applied to predict ductile fractures in high strength steel API X65. The model is implemented as a vectorized userdefined material subroutine (VUMAT) in the ABAQUS/Explicit commercial finite element code. Notched and smooth round bars under uniaxial tension loading are simulated to show the effect of equivalent plastic strain versus the void volume fraction growth of the material at and after crack initiation. Predictions of the ductile behavior from void nucleation to final failure stage are compared with the built-in Gurson – Tvergaard – Needleman (GTN) model in ABAQUS. Also, comparison with experimental results from the literature is discussed.