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Numerical Evaluation of Crack Initiation and Propagation in WC/Co Hardmetal under Monotonic Loads: a Comparative Study based on Conventional FEM and XFEM

  • : Utku Ahmet Özden1, Geng Chen1, Alexander Bezold1, Christoph Broeckmann1
  • : 1RWTH Aachen University
  • : PDF Download
  • : 2012

Abstract

Tungsten carbide-cobalt hardmetals (WC/Co) with high volume percent of WC (70-90 %) are interpenetrating microstructural composites whose two constitutive crystalline phases with widely differing properties (hard, brittle carbides and a tough metallic binder) contribute to one of the most technically successful materials currently in engineering use. Micro crack initiation and propagation in hardmetals under monotonic loading conditions has long been the interest of many researchers and different numerical approaches to predict the material damage behavior have been developed. In the framework of fracture mechanics, the accurate modeling of the deformation discontinuity and stress singularity near the crack front, as well as the precise evaluation of stress intensity factors and strain energy release rates are always in focus. Although conventional FEM has provided a mechanism to handle these kinds of problems, its lack of flexibility caused by requiring the user to define various properties, such as the crack tip and the normal of the crack surface, makes the method difficult to be applied in dealing with large scale and practical engineering problems. However, another approach on modeling of discontinues is the recently developed extended finite element method (XFEM) in which the discrete crack initiation and propagation, along an arbitrary solution dependent path, is possible without the crack front mesh conformability and predefined crack paths. In the current study, the micro crack initiation and propagation in WC/Co based on both conventional FEM and XFEM approaches are evaluated. In order to examine the potential of the XFEM approach, a 2D plane stress representative volume element (RVE) is generated based on SEM images of the material. Identical loading schemes and boundary conditions are applied and the evaluation of damage in both cases is compared on a theoretical and application basis.

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