異なる混合モード下における延性破壊の変化を予測するための結合力埋込型弾塑性構成則

Abstract

The contribution of this study is to propose a cohesive traction embedded constitutive law to predict the changes of ductile failure under different mixed mode. Flat and shear-lip fractures in ductile failure under different mixed mode are represented by the cohesive traction-separation law and shear-induced damage, respectively, reflecting that these mechanisms are different from each other. For the flat fracture, the stiffness reduction and strain softening due to void nucleation, growth, and coalescence under high stress state are realized by the cohesive traction-separation law that determines the process of stress releases along with ductile crack opening. To realize crack nucleation at an arbitrary location and propagation in an arbitrary direction, the cohesive separation law is combined with the Hencky-type hyperelastic-plastic model by the introduction of apparent deformation gradient due to crack opening and local balance equations between cohesive tractions and principal stresses. On the other hand, for the shear-lip fracture, the shrink of yield surface caused from the evolutions of micro voids in a shear band is represented by the shear-induced damage variable that is incorporated into the Tresca yield function. Moreover, the evolution of shear-induced damage is determined by the damage loading function corresponding to the plastic energy release based on thermodynamics. Simple numerical examples are presented to demonstrate that our proposed model enables us to predict the change of ductile fracture under different mixed mode.