Implementation of Virtual Internal Bond model to investigate fracture behavior in quasi brittle material

Abstract

The Virtual Internal Bond is a model in which domain is assumed to be consisting of material points connected through random virtual internal bonds and behavior of bond is describe through Xu Needleman potential function. This function basically encompasses normal and tangential separation and hence capable to capture mode I and mode II fracture. The speciality of virtual internal bond model is that crack initiation, propagation and complete fracture mechanism is in built using constitutive model and hence no separate fracture criteria are required. Virtual Internal Bond model is implement by using vu-mat subroutine code, this is a mathematical code written in FORTRAN language, which describe the constitutive relation of unit cell. Implementation of virtual internal bond model is used to solved different problems such plate with a hole, inclined notch in a plate and three-point bending. The simulation test carried out for a plate with hole problem revealed that the response of the model is insensitive to element type, mesh density, mesh layout. Also, simulation test is carried for an inclined notch in a plate problem to check response for that material. VIB is applied in uniaxial, biaxial and triaxial loading problem, which shows that for triaxial problem peak stress value occurs less critical strain value. Hence triaxial loading is more dangerous while investigating fracture behavior in material. The Three point bending test is carried out on UTM machine and investigate behavior in brittle material i.e. concrete beam to revealed that fracture behavior is carried out by stretching in bond. Also examined nonlinear effect developed due to non-homogenous property. Our developed code is capable successive capture mode I and mode II fracture.