STRAIN INJECTION, MIXED FORMULATIONS AND STRONG DISCONTINUITIES IN FRACTURE MODELING OF QUASI-BRITTLE MATERIALS

DIAS I.; OLIVER J; A.E HUESPE

Coimbra

Congreso; Congress on Numerical Methods in Engineering 2011; 2011

Associação Portuguesa de Mecânica Teórica, Aplicada e Computacional in association with SEMNI – Sociedad Española de Métodos Numéricos en Ingeniería

The presented work explores a combination of strain localization methods and strongdiscontinuity approaches to remove the flaws (stress-locking and mesh bias dependence) of theclassical strain localization methods, and reduce the sophistication of the strong-discontinuitybased methods (avoiding tracking algorithms). The concept of strong discontinuity is initiallysubstituted by that of weak discontinuity capturing the displacement jump through its distribution(smearing) in a finite length: the oriented with of a finite element through which the fracturepasses in a rather diffuse manner. In other words, the classical strain localization concept isbrought to the approach, no strong discontinuity enrichment is made and standard constitutivemodels are used in a classical strain localization setting. However, in order to remove thespurious mesh orientation dependence, constant strain localization modes are injected, via mixedfinite elements formulations, to the path of elements that are going to capture the cracks.Moreover, in a second stage, and in order to minimize stress locking, the elemental kinematics isenhanced by the injection of an elemental strong discontinuity mode, to those elements thatbelong to the localization band. These modes, as well as their injection time, are characterizedfrom the information provided by the SDA. Then, the obtained approach enjoys the benefits of thestrong discontinuities one, at a complexity similar to the classical, and simpler, localizationmethods. Representative numerical applications are presented in the final part of the paper.