STRAIN LOCALIZATION, STRONG DISCONTINUITIES AND MATERIAL FRACTURE: MATCHES, MISMATCHES AND STRAIN INJECTION PROCEDURES

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

San Pablo

Congreso; 10th World Congress on Computational Mechanics (WCCM-2012), San Pablo, Brasil, 8-13 Julio 201210th World Congress on Computational Mechanics (WCCM-2012),; 2012

IACM

The work explores the links of classical strain localization methods and strongdiscontinuity approaches for the purposes of modelling material failure in quasibrittlematerials.First, a procedure to evaluate the quality of the strain-localization results, interms of some proposed localization indicators that measure its match/mismatchwith a strong discontinuity embedded into the localization band, is presentedand assessed by comparison with some classical benchmarks.Then, the so-called strain injection procedures applied to computational modelingof material failure are presented. A combination of strain localization techniquesand strong discontinuity kinematics is used to remove the typical flaws (stresslockingand mesh bias dependence) of the classical strain localization methods,and reduce the sophistication of the strong-discontinuity based methods(avoiding tracking algorithms). The concept of strong discontinuity is initiallysubstituted by that of weak discontinuity capturing the displacement jumpthrough its distribution (smearing) in a finite length: the oriented with of a finiteelement through which the fracture passes in a rather diffuse manner. In otherwords, the classical strain localization concept is brought to the approach, nostrong discontinuity enrichment is made and standard constitutive models areused in a classical strain localization setting. However, in order to remove thespurious mesh orientation dependence, constant strain localization modes areinjected, via mixed finite elements formulations, to the path of elements that aregoing to capture the cracks. Moreover, in a second stage, and in order tominimize stress locking, the elemental kinematics is enhanced by the injection ofan elemental strong discontinuity mode, to those elements that belong to thelocalization band. These modes, as well as their injection time, are characterizedfrom the information provided by the SDA. Then, the obtained approach enjoysthe benefits of the strong discontinuities one, at a complexity similar to theclassical, and simpler, localization methods. Representative numericalapplications illustrate the performance of the method.