Browsing by Author "Hartmaier, Alexander"
Now showing 1 - 1 of 1
- Results Per Page
- Sort Options
Item Open Access Modeling of crack-tip plasticity in tungsten single crystals(2000) Hartmaier, Alexander; Arzt, Eduard (Prof. Dr. phil.)Many materials exhibit a transition from brittle behavior at low temperatures to ductile response at higher temperatures. The mechanisms controlling this brittle-to-ductile transition (BDT) remain unclear despite the large efforts made in experimental and theoretical investigations. In particular, the question whether it is dislocation nucleation or dislocation mobility which controls crack-tip plasticity and thus the brittle-to-ductile transition is still unanswered. This problem is tackled again here by studying the plastic deformation of the crack-tip region on the basis of discrete dislocation models. The results of the numerical studies performed in this work and their comparison with the results of an experimental study on tungsten single crystals leads to new insights on crack-tip plasticity and the BDT. The results are valid primarily for tungsten, but it can safely be assumed that they are transferable at least to other transition metals. A main conclusion drawn in this work is that crack-tip plasticity is limited by dislocation nucleation in well-annealed material at low temperatures. The lack of active dislocation sources prevents the emission of a sufficient number of dislocations to provide an efficient shielding of the crack tip. At higher temperatures the dislocation sources along the crack front become increasingly active and dislocation mobility starts to limit crack-tip plasticity and thus fracture toughness. The dislocations, which are generated in larger numbers, cannot leave the crack-tip region fast enough and thus inhibit the instantaneous nucleation of further dislocations.