Mixed finite element formulations and localized strain injection in fracture modeling of Quasi-brittle materials

J. OLIVER; I.F.DIAS; A.E. HUESPE

Barrcelona

Conferencia; Int. Conf. on Comput. Modeling of Fracture and Failure of Materials and Struct. (CFRAC-2011); 2011

ECCOMAS

The presented work explores a combination of strain localization methods [1] and strongdiscontinuity approaches [2] to remove the flaws (stress-locking and mesh bias dependence) of theclassical strain localization methods, and reduce the sophistication of the strong-discontinuity basedmethods (avoid tracking algorithms). The concept of strong discontinuity is initially substituted bythat of weak discontinuity capturing the displacement jump through its distribution (smearing) in afinite length: the oriented with of a finite element through which the fracture passes in a ratherdiffuse manner. In other words, the classical strain localization concept is brought to the approach, nostrong discontinuity enrichment is made and standard constitutive models are used in a classicalstrain localization setting. The standard mesh refinement recovers the strong discontinuity concept bytaking the element width to zero. However, in order to remove the spurious mesh orientationdependence, in a second stage specific localization modes are injected, via mixed finite elementsformulations, to the path of elements that are going to capture the cracks. These modes, as well astheir injection time, are characterized from the information provided by the SDA. Then, the obtainedapproach enjoys the benefits of the strong discontinuities one, at a complexity similar to the classical,and simpler, localization methods. Representative numerical applications are presented in the finalpart of the paper.