Dynamic failure simulation of quasi‐brittle material in dual particle dynamics

Abstract

The feasibility of simulating dynamic fracture in quasi-brittle material using a dual particle computational method with a smeared-crack representation of material failure is explored. The computational approach utilized is dual particle dynamics, which incorporates a moving least squares interpolation of field variables between two sets of particles that discretize the spatial domain, and a Lagrangian description of the moving least squares weight function. Material failure is represented by an inelastic continuum strain contribution obtained from smearing the effect of a cohesive failure model over a discrete volume of material. A threedimensional simulation of the initiation and development of a dynamic mode I failure is performed for the case of approximate plane wave propagation. Post failure wave interaction with the resulting global failure surface replicates the behavior of a stress-free boundary condition. The computational material failure approach is applied to problems of spalling in split Hopkinson pressure bar tests. Experimental failure trends are reproduced successfully.The use of zero thickness interface elements placed along inter-element boundaries is a widely used approach for simulation of material failure [2,3]. In this failure representation, the discrete constitutive model (traction versus displacement discontinuity) is applied across the interface element to model localization and fracture. The downside of using interface elements is that the macro-crack trajectory is restricted to follow the element boundaries. Consequently, the results are always mesh dependent. A summary of interface elements is provided by Rots [4].Computational failure methods based on automatic mesh generation have also been utilized [5,6]. Like the interface element method, cracks are confined to element boundaries, but the mesh structure changes throughout the computation to accommodate the changing crack path. The discontinuity is the result of the changing mesh structure, and remeshing only needs to be performed locally near the crack tip. The drawback of this approach is the complicated implementation of the automated meshing procedure and the potentially high computational cost of remeshing many times throughout the course of the simulation.The smeared-crack representation of material failure utilizes a classical continuum description of the problem. In this method, also known as a crack band model [7], the fracture process zone is idealized as a band of finite width, as opposed to a discrete surface. The effect of localization within the band is represented by an inelastic strain contribution. Consequently, the effect of failure is "smeared" across the width of the band. The smeared-crack approach has been utilized to model failure of concrete structures [8,9]. A thorough overview of smeared-crack models is provided by Rots [4,10,11]. Implementation of smeared-crack failure representation is straightforward and can be done with minimal changes to existing codes. Limitations of the method in FEM are mesh orien...

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