Thursday, August 28, 2014

Orientation Dependence of the Fracture Behavior of Single-crystal Tungsten ☆


Polycrystalline tungsten at room temperature shows a brittle fracture behavior, which is also strongly influenced by the grain structure and texture as well as sample dimensions. To gain insight into the mechanical response of individual grains, an experimental program has been set up to test small scale samples under microbending starting with a notched tungsten single crystal oriented with the {110}<> crack system along the loading direction. Related to this experimental program a finite element study has been performed to analyze the crack propagation in such single-crystal tungsten micro cantilevers. The aim of the present numerical work is to investigate the influence of the single-crystal orientation on the fracture process.
A finite element (FE) model of the notched microbeam was created taking plastic deformation at the crack tip into account. Plastic deformation is implemented using a crystal plasticity approach formulated by Asaro (1983) and written by Huang (1991). Furthermore, the fracture process with crack propagation is described by a cohesive zone model. The simulations of microbending allow for evaluating the details of the fracture process more accurately. The results reveal details of the developing plastic zone as well as the current crack propagation and the J-integral in dependence of the crystal orientation and notch geometry.

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