EVOLUTION OF CRACK-TIP PROCESS ZONES

A variety of crack tip profiles can appear under the fracture processes controlled by an anisotropic damage law taking into account the deterioration effects of plastic flow, stress triaxiality and initial draw direction. When combined with a hyperelastic and viscoplastic constitutive framework at finite deformation, the anisotropic damage theory enables us to simulate numerically five typical crack tip profiles: crack tip superblunting, a branching or spearhead profile, trident damage channeling, sharp notch and blunted notch. To obtain a combined micro/macroscopic appreciation on interfacial fracture along a metal/ceramic interface, a triple-layer configuration is proposed which consists of a nanoscopic core disc made by atomistic assembly, an overlapping elastic annulus incorporating discrete plasticity accumulated by dislocation motion, and an enveloping macroscopic layer described by an elastic-viscoplastic continuum. Preliminary computations are conducted to characterize the zigzag formation of a thermally adhered metal/ceramic interface, to delineate the atomistic determination of interfacial fracture patterns, and to simulate the transmission of crack tip dislocations from the atomistic assembly to the overlapping continuum.