Analysis of uniaxial tensile fracture of monomineral polycrystalline rock based on intergranular cracking

摘要

A finite element analysis of uniaxial tensile fracture was performed for specimen models of monomineral polycrystalline rock under the assumption that fracturing occurs only at the grain boundaries. The constitutive law of the grain boundaries was derived by applying the associated flow rule in the plastic theory and a tension-shear-softening curve to an extended Coulomb criterion. Unloading of intergranular cracks occurs before the peak strength when the intergranular cracks do not compose the final failure plane that is completely formed near the inflection point of the axial stress-axial strain curve after the peak. During the completion of the final failure plane, the conversion of failure mode from tension to shear occurs at intergranular cracks that have a large angle of the normal direction relative to the loading axis, for which the normal stress is in compression in both the initial elastic stage and the final failure stage.